@@ -11,8 +11,8 @@ "github.com/iden3/go-iden3-crypto/babyjub"
 )
 
 const (
-	// L1TxBytesLen is the length of the byte array that represents the L1Tx
-	L1TxBytesLen = 72
+	// L1UserTxBytesLen is the length of the byte array that represents the L1Tx
+	L1UserTxBytesLen = 72
 	// L1CoordinatorTxBytesLen is the length of the byte array that represents the L1CoordinatorTx
 	L1CoordinatorTxBytesLen = 101
 )
@@ -27,20 +27,20 @@ // values: | type | ToForgeL1TxsNum | Position | 0 (padding) |
 	// where type:
 	// 	- L1UserTx: 0
 	// 	- L1CoordinatorTx: 1
-	TxID            TxID
-	ToForgeL1TxsNum *int64 // toForgeL1TxsNum in which the tx was forged / will be forged
-	Position        int
-	UserOrigin      bool // true if the tx was originated by a user, false if it was aoriginated by a coordinator. Note that this differ from the spec for implementation simplification purpposes
-	FromIdx         Idx  // FromIdx is used by L1Tx/Deposit to indicate the Idx receiver of the L1Tx.LoadAmount (deposit)
-	FromEthAddr     ethCommon.Address
-	FromBJJ         *babyjub.PublicKey
-	ToIdx           Idx // ToIdx is ignored in L1Tx/Deposit, but used in the L1Tx/DepositAndTransfer
-	TokenID         TokenID
-	Amount          *big.Int
-	LoadAmount      *big.Int
-	EthBlockNum     int64 // Ethereum Block Number in which this L1Tx was added to the queue
-	Type            TxType
-	BatchNum        *BatchNum
+	TxID            TxID               `meddler:"id"`
+	ToForgeL1TxsNum *int64             `meddler:"to_forge_l1_txs_num"` // toForgeL1TxsNum in which the tx was forged / will be forged
+	Position        int                `meddler:"position"`
+	UserOrigin      bool               `meddler:"user_origin"`         // true if the tx was originated by a user, false if it was aoriginated by a coordinator. Note that this differ from the spec for implementation simplification purpposes
+	FromIdx         Idx                `meddler:"from_idx,zeroisnull"` // FromIdx is used by L1Tx/Deposit to indicate the Idx receiver of the L1Tx.LoadAmount (deposit)
+	FromEthAddr     ethCommon.Address  `meddler:"from_eth_addr,zeroisnull"`
+	FromBJJ         *babyjub.PublicKey `meddler:"from_bjj,zeroisnull"`
+	ToIdx           Idx                `meddler:"to_idx"` // ToIdx is ignored in L1Tx/Deposit, but used in the L1Tx/DepositAndTransfer
+	TokenID         TokenID            `meddler:"token_id"`
+	Amount          *big.Int           `meddler:"amount,bigint"`
+	LoadAmount      *big.Int           `meddler:"load_amount,bigint"`
+	EthBlockNum     int64              `meddler:"eth_block_num"` // Ethereum Block Number in which this L1Tx was added to the queue
+	Type            TxType             `meddler:"type"`
+	BatchNum        *BatchNum          `meddler:"batch_num"`
 }
 
 // NewL1Tx returns the given L1Tx with the TxId & Type parameters calculated
@@ -146,9 +146,9 @@ }
 	return genericTx
 }
 
-// Bytes encodes a L1Tx into []byte
-func (tx *L1Tx) Bytes() ([]byte, error) {
-	var b [L1TxBytesLen]byte
+// BytesUser encodes a L1Tx into []byte
+func (tx *L1Tx) BytesUser() ([]byte, error) {
+	var b [L1UserTxBytesLen]byte
 	copy(b[0:20], tx.FromEthAddr.Bytes())
 	pkCompL := tx.FromBJJ.Compress()
 	pkCompB := SwapEndianness(pkCompL[:])
@@ -193,13 +193,15 @@ copy(b[97:101], tx.TokenID.Bytes())
 	return b[:], nil
 }
 
-// L1TxFromBytes decodes a L1Tx from []byte
-func L1TxFromBytes(b []byte) (*L1Tx, error) {
-	if len(b) != L1TxBytesLen {
+// L1UserTxFromBytes decodes a L1Tx from []byte
+func L1UserTxFromBytes(b []byte) (*L1Tx, error) {
+	if len(b) != L1UserTxBytesLen {
 		return nil, fmt.Errorf("Can not parse L1Tx bytes, expected length %d, current: %d", 68, len(b))
 	}
 
-	tx := &L1Tx{}
+	tx := &L1Tx{
+		UserOrigin: true,
+	}
 	var err error
 	tx.FromEthAddr = ethCommon.BytesToAddress(b[0:20])
 
@@ -231,8 +233,8 @@
 	return tx, nil
 }
 
-// L1TxFromCoordinatorBytes decodes a L1Tx from []byte
-func L1TxFromCoordinatorBytes(b []byte) (*L1Tx, error) {
+// L1CoordinatorTxFromBytes decodes a L1Tx from []byte
+func L1CoordinatorTxFromBytes(b []byte) (*L1Tx, error) {
 	if len(b) != L1CoordinatorTxBytesLen {
 		return nil, fmt.Errorf("Can not parse L1CoordinatorTx bytes, expected length %d, current: %d", 101, len(b))
 	}
@@ -240,7 +242,9 @@
 	bytesMessage1 := []byte("\x19Ethereum Signed Message:\n98")
 	bytesMessage2 := []byte("I authorize this babyjubjub key for hermez rollup account creation")
 
-	tx := &L1Tx{}
+	tx := &L1Tx{
+		UserOrigin: false,
+	}
 	var err error
 	// Ethereum adds 27 to v
 	v := b[0] - byte(27) //nolint:gomnd

@@ -49,7 +49,7 @@ assert.Nil(t, err)
 	assert.Equal(t, "0x01000000000000cafe005800", l1Tx.TxID.String())
 }
 
-func TestL1TxByteParsers(t *testing.T) {
+func TestL1userTxByteParsers(t *testing.T) {
 	var pkComp babyjub.PublicKeyComp
 	pkCompL := []byte("0x56ca90f80d7c374ae7485e9bcc47d4ac399460948da6aeeb899311097925a72c")
 	err := pkComp.UnmarshalText(pkCompL)
@@ -59,6 +59,7 @@ pk, err := pkComp.Decompress()
 	require.Nil(t, err)
 
 	l1Tx := &L1Tx{
+		UserOrigin:  true,
 		ToIdx:       3,
 		TokenID:     5,
 		Amount:      big.NewInt(1),
@@ -68,21 +69,21 @@ FromBJJ:     pk,
 		FromEthAddr: ethCommon.HexToAddress("0xc58d29fA6e86E4FAe04DDcEd660d45BCf3Cb2370"),
 	}
 
-	encodedData, err := l1Tx.Bytes()
+	encodedData, err := l1Tx.BytesUser()
 	require.Nil(t, err)
-	decodedData, err := L1TxFromBytes(encodedData)
+	decodedData, err := L1UserTxFromBytes(encodedData)
 	require.Nil(t, err)
 	assert.Equal(t, l1Tx, decodedData)
-	encodedData2, err := decodedData.Bytes()
+	encodedData2, err := decodedData.BytesUser()
 	require.Nil(t, err)
 	assert.Equal(t, encodedData, encodedData2)
 
 	// expect error if length!=68
-	_, err = L1TxFromBytes(encodedData[:66])
+	_, err = L1UserTxFromBytes(encodedData[:66])
 	require.NotNil(t, err)
-	_, err = L1TxFromBytes([]byte{})
+	_, err = L1UserTxFromBytes([]byte{})
 	require.NotNil(t, err)
-	_, err = L1TxFromBytes(nil)
+	_, err = L1UserTxFromBytes(nil)
 	require.NotNil(t, err)
 }
 
@@ -113,7 +114,7 @@
 	expected, err := utils.HexDecode("85dab5b9e2e361d0c208d77be90efcc0439b0a530dd02deb2c81068e7a0f7e327df80b4ab79ee1f41a7def613e73a20c32eece5a000001c638db8be880f00020039c0000053cb88d")
 	require.Nil(t, err)
 
-	encodedData, err := l1Tx.Bytes()
+	encodedData, err := l1Tx.BytesUser()
 	require.Nil(t, err)
 	assert.Equal(t, expected, encodedData)
 }
@@ -161,7 +162,7 @@ }
 
 	bytesCoordinatorL1, err := l1Tx.BytesCoordinatorTx(signature)
 	require.Nil(t, err)
-	l1txDecoded, err := L1TxFromCoordinatorBytes(bytesCoordinatorL1)
+	l1txDecoded, err := L1CoordinatorTxFromBytes(bytesCoordinatorL1)
 	require.Nil(t, err)
 	assert.Equal(t, l1Tx, l1txDecoded)
 	bytesCoordinatorL12, err := l1txDecoded.BytesCoordinatorTx(signature)
@@ -169,11 +170,11 @@ require.Nil(t, err)
 	assert.Equal(t, bytesCoordinatorL1, bytesCoordinatorL12)
 
 	// expect error if length!=68
-	_, err = L1TxFromCoordinatorBytes(bytesCoordinatorL1[:66])
+	_, err = L1CoordinatorTxFromBytes(bytesCoordinatorL1[:66])
 	require.NotNil(t, err)
-	_, err = L1TxFromCoordinatorBytes([]byte{})
+	_, err = L1CoordinatorTxFromBytes([]byte{})
 	require.NotNil(t, err)
-	_, err = L1TxFromCoordinatorBytes(nil)
+	_, err = L1CoordinatorTxFromBytes(nil)
 	require.NotNil(t, err)
 }
 

@@ -265,7 +265,7 @@ type AuctionClient struct {
 	client       *EthereumClient
 	address      ethCommon.Address
 	tokenAddress ethCommon.Address
-	gasLimit     uint64
+	auction      *HermezAuctionProtocol.HermezAuctionProtocol
 	contractAbi  abi.ABI
 }
 
@@ -275,11 +275,15 @@ contractAbi, err := abi.JSON(strings.NewReader(string(HermezAuctionProtocol.HermezAuctionProtocolABI)))
 	if err != nil {
 		return nil, err
 	}
+	auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(address, client.Client())
+	if err != nil {
+		return nil, err
+	}
 	return &AuctionClient{
 		client:       client,
 		address:      address,
 		tokenAddress: tokenAddress,
-		gasLimit:     1000000, //nolint:gomnd
+		auction:      auction,
 		contractAbi:  contractAbi,
 	}, nil
 }
@@ -289,13 +293,9 @@ func (c *AuctionClient) AuctionSetSlotDeadline(newDeadline uint8) (*types.Transaction, error) {
 	var tx *types.Transaction
 	var err error
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
-			auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-			if err != nil {
-				return nil, err
-			}
-			return auction.SetSlotDeadline(auth, newDeadline)
+			return c.auction.SetSlotDeadline(auth, newDeadline)
 		},
 	); err != nil {
 		return nil, fmt.Errorf("Failed setting slotDeadline: %w", err)
@@ -304,14 +304,9 @@ return tx, nil
 }
 
 // AuctionGetSlotDeadline is the interface to call the smart contract function
-func (c *AuctionClient) AuctionGetSlotDeadline() (uint8, error) {
-	var slotDeadline uint8
+func (c *AuctionClient) AuctionGetSlotDeadline() (slotDeadline uint8, err error) {
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-		if err != nil {
-			return err
-		}
-		slotDeadline, err = auction.GetSlotDeadline(nil)
+		slotDeadline, err = c.auction.GetSlotDeadline(nil)
 		return err
 	}); err != nil {
 		return 0, err
@@ -320,17 +315,11 @@ return slotDeadline, nil
 }
 
 // AuctionSetOpenAuctionSlots is the interface to call the smart contract function
-func (c *AuctionClient) AuctionSetOpenAuctionSlots(newOpenAuctionSlots uint16) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *AuctionClient) AuctionSetOpenAuctionSlots(newOpenAuctionSlots uint16) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
-			auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-			if err != nil {
-				return nil, err
-			}
-			return auction.SetOpenAuctionSlots(auth, newOpenAuctionSlots)
+			return c.auction.SetOpenAuctionSlots(auth, newOpenAuctionSlots)
 		},
 	); err != nil {
 		return nil, fmt.Errorf("Failed setting openAuctionSlots: %w", err)
@@ -339,14 +328,9 @@ return tx, nil
 }
 
 // AuctionGetOpenAuctionSlots is the interface to call the smart contract function
-func (c *AuctionClient) AuctionGetOpenAuctionSlots() (uint16, error) {
-	var openAuctionSlots uint16
+func (c *AuctionClient) AuctionGetOpenAuctionSlots() (openAuctionSlots uint16, err error) {
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-		if err != nil {
-			return err
-		}
-		openAuctionSlots, err = auction.GetOpenAuctionSlots(nil)
+		openAuctionSlots, err = c.auction.GetOpenAuctionSlots(nil)
 		return err
 	}); err != nil {
 		return 0, err
@@ -355,17 +339,11 @@ return openAuctionSlots, nil
 }
 
 // AuctionSetClosedAuctionSlots is the interface to call the smart contract function
-func (c *AuctionClient) AuctionSetClosedAuctionSlots(newClosedAuctionSlots uint16) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *AuctionClient) AuctionSetClosedAuctionSlots(newClosedAuctionSlots uint16) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
-			auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-			if err != nil {
-				return nil, err
-			}
-			return auction.SetClosedAuctionSlots(auth, newClosedAuctionSlots)
+			return c.auction.SetClosedAuctionSlots(auth, newClosedAuctionSlots)
 		},
 	); err != nil {
 		return nil, fmt.Errorf("Failed setting closedAuctionSlots: %w", err)
@@ -374,14 +352,9 @@ return tx, nil
 }
 
 // AuctionGetClosedAuctionSlots is the interface to call the smart contract function
-func (c *AuctionClient) AuctionGetClosedAuctionSlots() (uint16, error) {
-	var closedAuctionSlots uint16
+func (c *AuctionClient) AuctionGetClosedAuctionSlots() (closedAuctionSlots uint16, err error) {
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-		if err != nil {
-			return err
-		}
-		closedAuctionSlots, err = auction.GetClosedAuctionSlots(nil)
+		closedAuctionSlots, err = c.auction.GetClosedAuctionSlots(nil)
 		return err
 	}); err != nil {
 		return 0, err
@@ -390,17 +363,11 @@ return closedAuctionSlots, nil
 }
 
 // AuctionSetOutbidding is the interface to call the smart contract function
-func (c *AuctionClient) AuctionSetOutbidding(newOutbidding uint16) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *AuctionClient) AuctionSetOutbidding(newOutbidding uint16) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
 		12500000, //nolint:gomnd
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
-			auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-			if err != nil {
-				return nil, err
-			}
-			return auction.SetOutbidding(auth, newOutbidding)
+			return c.auction.SetOutbidding(auth, newOutbidding)
 		},
 	); err != nil {
 		return nil, fmt.Errorf("Failed setting setOutbidding: %w", err)
@@ -409,14 +376,9 @@ return tx, nil
 }
 
 // AuctionGetOutbidding is the interface to call the smart contract function
-func (c *AuctionClient) AuctionGetOutbidding() (uint16, error) {
-	var outbidding uint16
+func (c *AuctionClient) AuctionGetOutbidding() (outbidding uint16, err error) {
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-		if err != nil {
-			return err
-		}
-		outbidding, err = auction.GetOutbidding(nil)
+		outbidding, err = c.auction.GetOutbidding(nil)
 		return err
 	}); err != nil {
 		return 0, err
@@ -425,17 +387,11 @@ return outbidding, nil
 }
 
 // AuctionSetAllocationRatio is the interface to call the smart contract function
-func (c *AuctionClient) AuctionSetAllocationRatio(newAllocationRatio [3]uint16) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *AuctionClient) AuctionSetAllocationRatio(newAllocationRatio [3]uint16) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
-			auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-			if err != nil {
-				return nil, err
-			}
-			return auction.SetAllocationRatio(auth, newAllocationRatio)
+			return c.auction.SetAllocationRatio(auth, newAllocationRatio)
 		},
 	); err != nil {
 		return nil, fmt.Errorf("Failed setting allocationRatio: %w", err)
@@ -444,14 +400,9 @@ return tx, nil
 }
 
 // AuctionGetAllocationRatio is the interface to call the smart contract function
-func (c *AuctionClient) AuctionGetAllocationRatio() ([3]uint16, error) {
-	var allocationRation [3]uint16
+func (c *AuctionClient) AuctionGetAllocationRatio() (allocationRation [3]uint16, err error) {
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-		if err != nil {
-			return err
-		}
-		allocationRation, err = auction.GetAllocationRatio(nil)
+		allocationRation, err = c.auction.GetAllocationRatio(nil)
 		return err
 	}); err != nil {
 		return [3]uint16{}, err
@@ -460,17 +411,11 @@ return allocationRation, nil
 }
 
 // AuctionSetDonationAddress is the interface to call the smart contract function
-func (c *AuctionClient) AuctionSetDonationAddress(newDonationAddress ethCommon.Address) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *AuctionClient) AuctionSetDonationAddress(newDonationAddress ethCommon.Address) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
-			auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-			if err != nil {
-				return nil, err
-			}
-			return auction.SetDonationAddress(auth, newDonationAddress)
+			return c.auction.SetDonationAddress(auth, newDonationAddress)
 		},
 	); err != nil {
 		return nil, fmt.Errorf("Failed setting donationAddress: %w", err)
@@ -479,33 +424,23 @@ return tx, nil
 }
 
 // AuctionGetDonationAddress is the interface to call the smart contract function
-func (c *AuctionClient) AuctionGetDonationAddress() (*ethCommon.Address, error) {
-	var donationAddress ethCommon.Address
+func (c *AuctionClient) AuctionGetDonationAddress() (donationAddress *ethCommon.Address, err error) {
+	var _donationAddress ethCommon.Address
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-		if err != nil {
-			return err
-		}
-		donationAddress, err = auction.GetDonationAddress(nil)
+		_donationAddress, err = c.auction.GetDonationAddress(nil)
 		return err
 	}); err != nil {
 		return nil, err
 	}
-	return &donationAddress, nil
+	return &_donationAddress, nil
 }
 
 // AuctionSetBootCoordinator is the interface to call the smart contract function
-func (c *AuctionClient) AuctionSetBootCoordinator(newBootCoordinator ethCommon.Address) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *AuctionClient) AuctionSetBootCoordinator(newBootCoordinator ethCommon.Address) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
-			auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-			if err != nil {
-				return nil, err
-			}
-			return auction.SetBootCoordinator(auth, newBootCoordinator)
+			return c.auction.SetBootCoordinator(auth, newBootCoordinator)
 		},
 	); err != nil {
 		return nil, fmt.Errorf("Failed setting bootCoordinator: %w", err)
@@ -514,34 +449,24 @@ return tx, nil
 }
 
 // AuctionGetBootCoordinator is the interface to call the smart contract function
-func (c *AuctionClient) AuctionGetBootCoordinator() (*ethCommon.Address, error) {
-	var bootCoordinator ethCommon.Address
+func (c *AuctionClient) AuctionGetBootCoordinator() (bootCoordinator *ethCommon.Address, err error) {
+	var _bootCoordinator ethCommon.Address
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-		if err != nil {
-			return err
-		}
-		bootCoordinator, err = auction.GetBootCoordinator(nil)
+		_bootCoordinator, err = c.auction.GetBootCoordinator(nil)
 		return err
 	}); err != nil {
 		return nil, err
 	}
-	return &bootCoordinator, nil
+	return &_bootCoordinator, nil
 }
 
 // AuctionChangeDefaultSlotSetBid is the interface to call the smart contract function
-func (c *AuctionClient) AuctionChangeDefaultSlotSetBid(slotSet int64, newInitialMinBid *big.Int) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *AuctionClient) AuctionChangeDefaultSlotSetBid(slotSet int64, newInitialMinBid *big.Int) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
-			auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-			if err != nil {
-				return nil, err
-			}
 			slotSetToSend := big.NewInt(slotSet)
-			return auction.ChangeDefaultSlotSetBid(auth, slotSetToSend, newInitialMinBid)
+			return c.auction.ChangeDefaultSlotSetBid(auth, slotSetToSend, newInitialMinBid)
 		},
 	); err != nil {
 		return nil, fmt.Errorf("Failed changing slotSet Bid: %w", err)
@@ -550,14 +475,9 @@ return tx, nil
 }
 
 // AuctionGetClaimableHEZ is the interface to call the smart contract function
-func (c *AuctionClient) AuctionGetClaimableHEZ(claimAddress ethCommon.Address) (*big.Int, error) {
-	var claimableHEZ *big.Int
+func (c *AuctionClient) AuctionGetClaimableHEZ(claimAddress ethCommon.Address) (claimableHEZ *big.Int, err error) {
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-		if err != nil {
-			return err
-		}
-		claimableHEZ, err = auction.GetClaimableHEZ(nil, claimAddress)
+		claimableHEZ, err = c.auction.GetClaimableHEZ(nil, claimAddress)
 		return err
 	}); err != nil {
 		return nil, err
@@ -566,17 +486,11 @@ return claimableHEZ, nil
 }
 
 // AuctionSetCoordinator is the interface to call the smart contract function
-func (c *AuctionClient) AuctionSetCoordinator(forger ethCommon.Address, coordinatorURL string) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *AuctionClient) AuctionSetCoordinator(forger ethCommon.Address, coordinatorURL string) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
-			auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-			if err != nil {
-				return nil, err
-			}
-			return auction.SetCoordinator(auth, forger, coordinatorURL)
+			return c.auction.SetCoordinator(auth, forger, coordinatorURL)
 		},
 	); err != nil {
 		return nil, fmt.Errorf("Failed set coordinator: %w", err)
@@ -585,32 +499,22 @@ return tx, nil
 }
 
 // AuctionGetCurrentSlotNumber is the interface to call the smart contract function
-func (c *AuctionClient) AuctionGetCurrentSlotNumber() (int64, error) {
+func (c *AuctionClient) AuctionGetCurrentSlotNumber() (currentSlotNumber int64, err error) {
 	var _currentSlotNumber *big.Int
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-		if err != nil {
-			return err
-		}
-		_currentSlotNumber, err = auction.GetCurrentSlotNumber(nil)
+		_currentSlotNumber, err = c.auction.GetCurrentSlotNumber(nil)
 		return err
 	}); err != nil {
 		return 0, err
 	}
-	currentSlotNumber := _currentSlotNumber.Int64()
-	return currentSlotNumber, nil
+	return _currentSlotNumber.Int64(), nil
 }
 
 // AuctionGetMinBidBySlot is the interface to call the smart contract function
-func (c *AuctionClient) AuctionGetMinBidBySlot(slot int64) (*big.Int, error) {
-	var minBid *big.Int
+func (c *AuctionClient) AuctionGetMinBidBySlot(slot int64) (minBid *big.Int, err error) {
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-		if err != nil {
-			return err
-		}
 		slotToSend := big.NewInt(slot)
-		minBid, err = auction.GetMinBidBySlot(nil, slotToSend)
+		minBid, err = c.auction.GetMinBidBySlot(nil, slotToSend)
 		return err
 	}); err != nil {
 		return big.NewInt(0), err
@@ -619,15 +523,10 @@ return minBid, nil
 }
 
 // AuctionGetSlotSet is the interface to call the smart contract function
-func (c *AuctionClient) AuctionGetSlotSet(slot int64) (*big.Int, error) {
-	var slotSet *big.Int
+func (c *AuctionClient) AuctionGetSlotSet(slot int64) (slotSet *big.Int, err error) {
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-		if err != nil {
-			return err
-		}
 		slotToSend := big.NewInt(slot)
-		slotSet, err = auction.GetSlotSet(nil, slotToSend)
+		slotSet, err = c.auction.GetSlotSet(nil, slotToSend)
 		return err
 	}); err != nil {
 		return big.NewInt(0), err
@@ -636,14 +535,9 @@ return slotSet, nil
 }
 
 // AuctionGetDefaultSlotSetBid is the interface to call the smart contract function
-func (c *AuctionClient) AuctionGetDefaultSlotSetBid(slotSet uint8) (*big.Int, error) {
-	var minBidSlotSet *big.Int
+func (c *AuctionClient) AuctionGetDefaultSlotSetBid(slotSet uint8) (minBidSlotSet *big.Int, err error) {
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-		if err != nil {
-			return err
-		}
-		minBidSlotSet, err = auction.GetDefaultSlotSetBid(nil, slotSet)
+		minBidSlotSet, err = c.auction.GetDefaultSlotSetBid(nil, slotSet)
 		return err
 	}); err != nil {
 		return big.NewInt(0), err
@@ -652,28 +546,21 @@ return minBidSlotSet, nil
 }
 
 // AuctionGetSlotNumber is the interface to call the smart contract function
-func (c *AuctionClient) AuctionGetSlotNumber(blockNum int64) (int64, error) {
-	var slot *big.Int
+func (c *AuctionClient) AuctionGetSlotNumber(blockNum int64) (slot int64, err error) {
+	var _slot *big.Int
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-		if err != nil {
-			return err
-		}
-		blockNumBig := big.NewInt(blockNum)
-		slot, err = auction.GetSlotNumber(nil, blockNumBig)
+		_slot, err = c.auction.GetSlotNumber(nil, big.NewInt(blockNum))
 		return err
 	}); err != nil {
 		return 0, err
 	}
-	return slot.Int64(), nil
+	return _slot.Int64(), nil
 }
 
 // AuctionBid is the interface to call the smart contract function
-func (c *AuctionClient) AuctionBid(slot int64, bidAmount *big.Int) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *AuctionClient) AuctionBid(slot int64, bidAmount *big.Int) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
 			tokens, err := ERC777.NewERC777(c.tokenAddress, ec)
 			if err != nil {
@@ -703,11 +590,10 @@ return tx, nil
 }
 
 // AuctionMultiBid is the interface to call the smart contract function
-func (c *AuctionClient) AuctionMultiBid(startingSlot int64, endingSlot int64, slotSet [6]bool, maxBid, closedMinBid, budget *big.Int) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *AuctionClient) AuctionMultiBid(startingSlot int64, endingSlot int64, slotSet [6]bool,
+	maxBid, closedMinBid, budget *big.Int) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		1000000, //nolint:gomnd
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
 			tokens, err := ERC777.NewERC777(c.tokenAddress, ec)
 			if err != nil {
@@ -752,14 +638,9 @@ return tx, nil
 }
 
 // AuctionCanForge is the interface to call the smart contract function
-func (c *AuctionClient) AuctionCanForge(forger ethCommon.Address, blockNum int64) (bool, error) {
-	var canForge bool
+func (c *AuctionClient) AuctionCanForge(forger ethCommon.Address, blockNum int64) (canForge bool, err error) {
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-		if err != nil {
-			return err
-		}
-		canForge, err = auction.CanForge(nil, forger, big.NewInt(blockNum))
+		canForge, err = c.auction.CanForge(nil, forger, big.NewInt(blockNum))
 		return err
 	}); err != nil {
 		return false, err
@@ -768,17 +649,11 @@ return canForge, nil
 }
 
 // AuctionClaimHEZ is the interface to call the smart contract function
-func (c *AuctionClient) AuctionClaimHEZ() (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *AuctionClient) AuctionClaimHEZ() (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
-			auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-			if err != nil {
-				return nil, err
-			}
-			return auction.ClaimHEZ(auth)
+			return c.auction.ClaimHEZ(auth)
 		},
 	); err != nil {
 		return nil, fmt.Errorf("Failed claim HEZ: %w", err)
@@ -787,17 +662,11 @@ return tx, nil
 }
 
 // AuctionForge is the interface to call the smart contract function
-func (c *AuctionClient) AuctionForge(forger ethCommon.Address) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *AuctionClient) AuctionForge(forger ethCommon.Address) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
-			auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-			if err != nil {
-				return nil, err
-			}
-			return auction.Forge(auth, forger)
+			return c.auction.Forge(auth, forger)
 		},
 	); err != nil {
 		return nil, fmt.Errorf("Failed forge: %w", err)
@@ -806,31 +675,27 @@ return tx, nil
 }
 
 // AuctionConstants returns the Constants of the Auction Smart Contract
-func (c *AuctionClient) AuctionConstants() (*AuctionConstants, error) {
-	auctionConstants := new(AuctionConstants)
+func (c *AuctionClient) AuctionConstants() (auctionConstants *AuctionConstants, err error) {
+	auctionConstants = new(AuctionConstants)
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		auction, err := HermezAuctionProtocol.NewHermezAuctionProtocol(c.address, ec)
-		if err != nil {
-			return err
-		}
-		auctionConstants.BlocksPerSlot, err = auction.BLOCKSPERSLOT(nil)
+		auctionConstants.BlocksPerSlot, err = c.auction.BLOCKSPERSLOT(nil)
 		if err != nil {
 			return err
 		}
-		genesisBlock, err := auction.GenesisBlock(nil)
+		genesisBlock, err := c.auction.GenesisBlock(nil)
 		if err != nil {
 			return err
 		}
 		auctionConstants.GenesisBlockNum = genesisBlock.Int64()
-		auctionConstants.HermezRollup, err = auction.HermezRollup(nil)
+		auctionConstants.HermezRollup, err = c.auction.HermezRollup(nil)
 		if err != nil {
 			return err
 		}
-		auctionConstants.InitialMinimalBidding, err = auction.INITIALMINIMALBIDDING(nil)
+		auctionConstants.InitialMinimalBidding, err = c.auction.INITIALMINIMALBIDDING(nil)
 		if err != nil {
 			return err
 		}
-		auctionConstants.TokenHEZ, err = auction.TokenHEZ(nil)
+		auctionConstants.TokenHEZ, err = c.auction.TokenHEZ(nil)
 		return err
 	}); err != nil {
 		return nil, err
@@ -839,10 +704,9 @@ return auctionConstants, nil
 }
 
 // AuctionVariables returns the variables of the Auction Smart Contract
-func (c *AuctionClient) AuctionVariables() (*AuctionVariables, error) {
-	auctionVariables := new(AuctionVariables)
+func (c *AuctionClient) AuctionVariables() (auctionVariables *AuctionVariables, err error) {
+	auctionVariables = new(AuctionVariables)
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		var err error
 		auctionVariables.AllocationRatio, err = c.AuctionGetAllocationRatio()
 		if err != nil {
 			return err

@@ -5,6 +5,7 @@ "fmt"
 
 	"github.com/ethereum/go-ethereum/accounts"
 	ethKeystore "github.com/ethereum/go-ethereum/accounts/keystore"
+	ethCommon "github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/ethclient"
 )
 
@@ -29,14 +30,38 @@ AuctionClient
 	RollupClient
 }
 
+// RollupConfig is the configuration for the Rollup smart contract interface
+type RollupConfig struct {
+	Address ethCommon.Address
+}
+
+// AuctionConfig is the configuration for the Auction smart contract interface
+type AuctionConfig struct {
+	Address         ethCommon.Address
+	TokenHEZAddress ethCommon.Address
+}
+
+// ClientConfig is the configuration of the Client
+type ClientConfig struct {
+	Ethereum EthereumConfig
+	Rollup   RollupConfig
+	Auction  AuctionConfig
+}
+
 // NewClient creates a new Client to interact with Ethereum and the Hermez smart contracts.
-func NewClient(client *ethclient.Client, account *accounts.Account, ks *ethKeystore.KeyStore, config *EthereumConfig) *Client {
-	ethereumClient := NewEthereumClient(client, account, ks, config)
-	auctionClient := &AuctionClient{}
-	rollupCient := &RollupClient{}
+func NewClient(client *ethclient.Client, account *accounts.Account, ks *ethKeystore.KeyStore, cfg *ClientConfig) (*Client, error) {
+	ethereumClient := NewEthereumClient(client, account, ks, &cfg.Ethereum)
+	auctionClient, err := NewAuctionClient(ethereumClient, cfg.Auction.Address, cfg.Auction.TokenHEZAddress)
+	if err != nil {
+		return nil, err
+	}
+	rollupCient, err := NewRollupClient(ethereumClient, cfg.Rollup.Address, cfg.Auction.TokenHEZAddress)
+	if err != nil {
+		return nil, err
+	}
 	return &Client{
 		EthereumClient: *ethereumClient,
 		AuctionClient:  *auctionClient,
 		RollupClient:   *rollupCient,
-	}
+	}, nil
 }

@@ -8,7 +8,7 @@ )
 
 func TestClientInterface(t *testing.T) {
 	var c ClientInterface
-	client := NewClient(nil, nil, nil, nil)
+	client, _ := NewClient(nil, nil, nil, &ClientConfig{})
 	c = client
 	require.NotNil(t, c)
 }

@@ -301,3 +301,8 @@ Symbol:   symbol,
 		Decimals: uint64(decimals),
 	}, nil
 }
+
+// Client returns the internal ethclient.Client
+func (c *EthereumClient) Client() *ethclient.Client {
+	return c.client
+}

@@ -153,9 +153,9 @@ }
 
 // RollupEventL1UserTx is an event of the Rollup Smart Contract
 type RollupEventL1UserTx struct {
-	ToForgeL1TxsNum int64 // QueueIndex       *big.Int
-	Position        int   // TransactionIndex *big.Int
-	L1UserTx        common.L1Tx
+	// ToForgeL1TxsNum int64 // QueueIndex       *big.Int
+	// Position        int   // TransactionIndex *big.Int
+	L1UserTx common.L1Tx
 }
 
 // RollupEventL1UserTxAux is an event of the Rollup Smart Contract
@@ -173,7 +173,8 @@ }
 
 // RollupEventForgeBatch is an event of the Rollup Smart Contract
 type RollupEventForgeBatch struct {
-	BatchNum  int64
+	BatchNum int64
+	// Sender    ethCommon.Address
 	EthTxHash ethCommon.Hash
 }
 
@@ -279,7 +280,7 @@ //
 
 	RollupConstants() (*RollupPublicConstants, error)
 	RollupEventsByBlock(blockNum int64) (*RollupEvents, *ethCommon.Hash, error)
-	RollupForgeBatchArgs(ethCommon.Hash) (*RollupForgeBatchArgs, error)
+	RollupForgeBatchArgs(ethCommon.Hash) (*RollupForgeBatchArgs, *ethCommon.Address, error)
 }
 
 //
@@ -291,13 +292,17 @@ type RollupClient struct {
 	client          *EthereumClient
 	address         ethCommon.Address
 	tokenHEZAddress ethCommon.Address
-	gasLimit        uint64
+	hermez          *Hermez.Hermez
 	contractAbi     abi.ABI
 }
 
 // NewRollupClient creates a new RollupClient
 func NewRollupClient(client *EthereumClient, address ethCommon.Address, tokenHEZAddress ethCommon.Address) (*RollupClient, error) {
 	contractAbi, err := abi.JSON(strings.NewReader(string(Hermez.HermezABI)))
+	if err != nil {
+		return nil, err
+	}
+	hermez, err := Hermez.NewHermez(address, client.Client())
 	if err != nil {
 		return nil, err
 	}
@@ -305,22 +310,16 @@ return &RollupClient{
 		client:          client,
 		address:         address,
 		tokenHEZAddress: tokenHEZAddress,
-		gasLimit:        1000000, //nolint:gomnd
+		hermez:          hermez,
 		contractAbi:     contractAbi,
 	}, nil
 }
 
 // RollupForgeBatch is the interface to call the smart contract function
-func (c *RollupClient) RollupForgeBatch(args *RollupForgeBatchArgs) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *RollupClient) RollupForgeBatch(args *RollupForgeBatchArgs) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		1000000, //nolint:gomnd
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
-			hermez, err := Hermez.NewHermez(c.address, ec)
-			if err != nil {
-				return nil, err
-			}
 			rollupConst, err := c.RollupConstants()
 			if err != nil {
 				return nil, err
@@ -362,7 +361,7 @@ return nil, err
 				}
 				feeIdxCoordinator = append(feeIdxCoordinator, bytesFeeIdx[len(bytesFeeIdx)-int(lenBytes):]...)
 			}
-			return hermez.ForgeBatch(auth, newLastIdx, args.NewStRoot, args.NewExitRoot, l1CoordinatorBytes, l2DataBytes, feeIdxCoordinator, args.VerifierIdx, args.L1Batch, args.ProofA, args.ProofB, args.ProofC)
+			return c.hermez.ForgeBatch(auth, newLastIdx, args.NewStRoot, args.NewExitRoot, l1CoordinatorBytes, l2DataBytes, feeIdxCoordinator, args.VerifierIdx, args.L1Batch, args.ProofA, args.ProofB, args.ProofC)
 		},
 	); err != nil {
 		return nil, fmt.Errorf("Failed forge batch: %w", err)
@@ -373,11 +372,9 @@
 // RollupAddToken is the interface to call the smart contract function.
 // `feeAddToken` is the amount of HEZ tokens that will be paid to add the
 // token.  `feeAddToken` must match the public value of the smart contract.
-func (c *RollupClient) RollupAddToken(tokenAddress ethCommon.Address, feeAddToken *big.Int) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *RollupClient) RollupAddToken(tokenAddress ethCommon.Address, feeAddToken *big.Int) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
 			tokens, err := ERC777.NewERC777(c.tokenHEZAddress, ec)
 			if err != nil {
@@ -403,11 +400,9 @@ return tx, nil
 }
 
 // RollupWithdrawMerkleProof is the interface to call the smart contract function
-func (c *RollupClient) RollupWithdrawMerkleProof(fromBJJ *babyjub.PublicKey, tokenID uint32, numExitRoot, idx int64, amount *big.Int, siblings []*big.Int, instantWithdraw bool) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *RollupClient) RollupWithdrawMerkleProof(fromBJJ *babyjub.PublicKey, tokenID uint32, numExitRoot, idx int64, amount *big.Int, siblings []*big.Int, instantWithdraw bool) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
 			hermez, err := Hermez.NewHermez(c.address, ec)
 			if err != nil {
@@ -433,11 +428,9 @@ return nil, errTODO
 }
 
 // RollupL1UserTxERC20ETH is the interface to call the smart contract function
-func (c *RollupClient) RollupL1UserTxERC20ETH(fromBJJ *babyjub.PublicKey, fromIdx int64, loadAmount *big.Int, amount *big.Int, tokenID uint32, toIdx int64) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *RollupClient) RollupL1UserTxERC20ETH(fromBJJ *babyjub.PublicKey, fromIdx int64, loadAmount *big.Int, amount *big.Int, tokenID uint32, toIdx int64) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
 			hermez, err := Hermez.NewHermez(c.address, ec)
 			if err != nil {
@@ -469,11 +462,9 @@ return tx, nil
 }
 
 // RollupL1UserTxERC777 is the interface to call the smart contract function
-func (c *RollupClient) RollupL1UserTxERC777(fromBJJ *babyjub.PublicKey, fromIdx int64, loadAmount *big.Int, amount *big.Int, tokenID uint32, toIdx int64) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *RollupClient) RollupL1UserTxERC777(fromBJJ *babyjub.PublicKey, fromIdx int64, loadAmount *big.Int, amount *big.Int, tokenID uint32, toIdx int64) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
 			tokens, err := ERC777.NewERC777(c.tokenHEZAddress, ec)
 			if err != nil {
@@ -544,11 +535,9 @@ return registerTokensCount, nil
 }
 
 // RollupUpdateForgeL1L2BatchTimeout is the interface to call the smart contract function
-func (c *RollupClient) RollupUpdateForgeL1L2BatchTimeout(newForgeL1L2BatchTimeout int64) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *RollupClient) RollupUpdateForgeL1L2BatchTimeout(newForgeL1L2BatchTimeout int64) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
 			hermez, err := Hermez.NewHermez(c.address, ec)
 			if err != nil {
@@ -563,11 +552,9 @@ return tx, nil
 }
 
 // RollupUpdateFeeAddToken is the interface to call the smart contract function
-func (c *RollupClient) RollupUpdateFeeAddToken(newFeeAddToken *big.Int) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *RollupClient) RollupUpdateFeeAddToken(newFeeAddToken *big.Int) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
 			hermez, err := Hermez.NewHermez(c.address, ec)
 			if err != nil {
@@ -582,25 +569,21 @@ return tx, nil
 }
 
 // RollupConstants returns the Constants of the Rollup Smart Contract
-func (c *RollupClient) RollupConstants() (*RollupPublicConstants, error) {
-	rollupConstants := new(RollupPublicConstants)
+func (c *RollupClient) RollupConstants() (rollupConstants *RollupPublicConstants, err error) {
+	rollupConstants = new(RollupPublicConstants)
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		hermez, err := Hermez.NewHermez(c.address, ec)
-		if err != nil {
-			return err
-		}
-		absoluteMaxL1L2BatchTimeout, err := hermez.ABSOLUTEMAXL1L2BATCHTIMEOUT(nil)
+		absoluteMaxL1L2BatchTimeout, err := c.hermez.ABSOLUTEMAXL1L2BATCHTIMEOUT(nil)
 		if err != nil {
 			return err
 		}
 		rollupConstants.AbsoluteMaxL1L2BatchTimeout = int64(absoluteMaxL1L2BatchTimeout)
-		rollupConstants.TokenHEZ, err = hermez.TokenHEZ(nil)
+		rollupConstants.TokenHEZ, err = c.hermez.TokenHEZ(nil)
 		if err != nil {
 			return err
 		}
 		for i := int64(0); i < int64(LenVerifiers); i++ {
 			var newRollupVerifier RollupVerifierStruct
-			rollupVerifier, err := hermez.RollupVerifiers(nil, big.NewInt(i))
+			rollupVerifier, err := c.hermez.RollupVerifiers(nil, big.NewInt(i))
 			if err != nil {
 				return err
 			}
@@ -608,19 +591,19 @@ newRollupVerifier.MaxTx = rollupVerifier.MaxTx.Int64()
 			newRollupVerifier.NLevels = rollupVerifier.NLevels.Int64()
 			rollupConstants.Verifiers = append(rollupConstants.Verifiers, newRollupVerifier)
 		}
-		rollupConstants.HermezAuctionContract, err = hermez.HermezAuctionContract(nil)
+		rollupConstants.HermezAuctionContract, err = c.hermez.HermezAuctionContract(nil)
 		if err != nil {
 			return err
 		}
-		rollupConstants.HermezGovernanceDAOAddress, err = hermez.HermezGovernanceDAOAddress(nil)
+		rollupConstants.HermezGovernanceDAOAddress, err = c.hermez.HermezGovernanceDAOAddress(nil)
 		if err != nil {
 			return err
 		}
-		rollupConstants.SafetyAddress, err = hermez.SafetyAddress(nil)
+		rollupConstants.SafetyAddress, err = c.hermez.SafetyAddress(nil)
 		if err != nil {
 			return err
 		}
-		rollupConstants.WithdrawDelayerContract, err = hermez.WithdrawDelayerContract(nil)
+		rollupConstants.WithdrawDelayerContract, err = c.hermez.WithdrawDelayerContract(nil)
 		return err
 	}); err != nil {
 		return nil, err
@@ -670,12 +653,14 @@ err := c.contractAbi.Unpack(&L1UserTxAux, "L1UserTxEvent", vLog.Data)
 			if err != nil {
 				return nil, nil, err
 			}
-			L1Tx, err := common.L1TxFromBytes(L1UserTxAux.L1UserTx)
+			L1Tx, err := common.L1UserTxFromBytes(L1UserTxAux.L1UserTx)
 			if err != nil {
 				return nil, nil, err
 			}
-			L1UserTx.ToForgeL1TxsNum = new(big.Int).SetBytes(vLog.Topics[1][:]).Int64()
-			L1UserTx.Position = int(new(big.Int).SetBytes(vLog.Topics[2][:]).Int64())
+			toForgeL1TxsNum := new(big.Int).SetBytes(vLog.Topics[1][:]).Int64()
+			L1Tx.ToForgeL1TxsNum = &toForgeL1TxsNum
+			L1Tx.Position = int(new(big.Int).SetBytes(vLog.Topics[2][:]).Int64())
+			L1Tx.UserOrigin = true
 			L1UserTx.L1UserTx = *L1Tx
 			rollupEvents.L1UserTx = append(rollupEvents.L1UserTx, L1UserTx)
 		case logHermezAddToken:
@@ -690,6 +675,7 @@ case logHermezForgeBatch:
 			var forgeBatch RollupEventForgeBatch
 			forgeBatch.BatchNum = new(big.Int).SetBytes(vLog.Topics[1][:]).Int64()
 			forgeBatch.EthTxHash = vLog.TxHash
+			// forgeBatch.Sender = vLog.Address
 			rollupEvents.ForgeBatch = append(rollupEvents.ForgeBatch, forgeBatch)
 		case logHermezUpdateForgeL1L2BatchTimeout:
 			var updateForgeL1L2BatchTimeout struct {
@@ -724,20 +710,29 @@ }
 	return &rollupEvents, &blockHash, nil
 }
 
-// RollupForgeBatchArgs returns the arguments used in a ForgeBatch call in the Rollup Smart Contract in the given transaction
-func (c *RollupClient) RollupForgeBatchArgs(ethTxHash ethCommon.Hash) (*RollupForgeBatchArgs, error) {
+// RollupForgeBatchArgs returns the arguments used in a ForgeBatch call in the
+// Rollup Smart Contract in the given transaction, and the sender address.
+func (c *RollupClient) RollupForgeBatchArgs(ethTxHash ethCommon.Hash) (*RollupForgeBatchArgs, *ethCommon.Address, error) {
 	tx, _, err := c.client.client.TransactionByHash(context.Background(), ethTxHash)
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	txData := tx.Data()
 	method, err := c.contractAbi.MethodById(txData[:4])
 	if err != nil {
-		return nil, err
+		return nil, nil, err
+	}
+	receipt, err := c.client.client.TransactionReceipt(context.Background(), ethTxHash)
+	if err != nil {
+		return nil, nil, err
+	}
+	sender, err := c.client.client.TransactionSender(context.Background(), tx, receipt.Logs[0].BlockHash, receipt.Logs[0].Index)
+	if err != nil {
+		return nil, nil, err
 	}
 	var aux RollupForgeBatchArgsAux
 	if err := method.Inputs.Unpack(&aux, txData[4:]); err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	rollupForgeBatchArgs := RollupForgeBatchArgs{
 		L1Batch:               aux.L1Batch,
@@ -763,16 +758,16 @@ r := bytesL1Coordinator[33:65]
 		signature = append(signature, r[:]...)
 		signature = append(signature, s[:]...)
 		signature = append(signature, v)
-		l1Tx, err := common.L1TxFromCoordinatorBytes(bytesL1Coordinator)
+		l1Tx, err := common.L1CoordinatorTxFromBytes(bytesL1Coordinator)
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
 		rollupForgeBatchArgs.L1CoordinatorTxs = append(rollupForgeBatchArgs.L1CoordinatorTxs, *l1Tx)
 		rollupForgeBatchArgs.L1CoordinatorTxsAuths = append(rollupForgeBatchArgs.L1CoordinatorTxsAuths, signature)
 	}
 	rollupConsts, err := c.RollupConstants()
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	nLevels := rollupConsts.Verifiers[rollupForgeBatchArgs.VerifierIdx].NLevels
 	lenL2TxsBytes := int((nLevels/8)*2 + 2 + 1)
@@ -780,7 +775,7 @@ numTxsL2 := len(aux.L2TxsData) / lenL2TxsBytes
 	for i := 0; i < numTxsL2; i++ {
 		l2Tx, err := common.L2TxFromBytes(aux.L2TxsData[i*lenL2TxsBytes:(i+1)*lenL2TxsBytes], int(nLevels))
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
 		rollupForgeBatchArgs.L2TxsData = append(rollupForgeBatchArgs.L2TxsData, *l2Tx)
 	}
@@ -796,11 +791,11 @@ copy(paddedFeeIdx[:], aux.FeeIdxCoordinator[i*lenFeeIdxCoordinatorBytes:(i+1)*lenFeeIdxCoordinatorBytes])
 		}
 		feeIdxCoordinator, err := common.IdxFromBytes(paddedFeeIdx[:])
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
 		if feeIdxCoordinator != common.Idx(0) {
 			rollupForgeBatchArgs.FeeIdxCoordinator = append(rollupForgeBatchArgs.FeeIdxCoordinator, feeIdxCoordinator)
 		}
 	}
-	return &rollupForgeBatchArgs, nil
+	return &rollupForgeBatchArgs, &sender, nil
 }

@@ -152,7 +152,7 @@ r := bytesL1Coordinator[33:65]
 		signature = append(signature, r[:]...)
 		signature = append(signature, s[:]...)
 		signature = append(signature, v)
-		l1Tx, err := common.L1TxFromCoordinatorBytes(bytesL1Coordinator)
+		l1Tx, err := common.L1CoordinatorTxFromBytes(bytesL1Coordinator)
 		require.Nil(t, err)
 		args.L1CoordinatorTxs = append(args.L1CoordinatorTxs, *l1Tx)
 		args.L1CoordinatorTxsAuths = append(args.L1CoordinatorTxsAuths, signature)
@@ -190,8 +190,9 @@ ethHashForge = rollupEvents.ForgeBatch[0].EthTxHash
 }
 
 func TestRollupForgeBatchArgs(t *testing.T) {
-	args, err := rollupClient.RollupForgeBatchArgs(ethHashForge)
+	args, sender, err := rollupClient.RollupForgeBatchArgs(ethHashForge)
 	require.Nil(t, err)
+	assert.Equal(t, *sender, rollupClient.client.account.Address)
 	assert.Equal(t, argsForge.FeeIdxCoordinator, args.FeeIdxCoordinator)
 	assert.Equal(t, argsForge.L1Batch, args.L1Batch)
 	assert.Equal(t, argsForge.L1CoordinatorTxs, args.L1CoordinatorTxs)

@@ -136,52 +136,46 @@ // WDelayerClient is the implementation of the interface to the WithdrawDelayer Smart Contract in ethereum.
 type WDelayerClient struct {
 	client      *EthereumClient
 	address     ethCommon.Address
-	gasLimit    uint64
+	wdelayer    *WithdrawalDelayer.WithdrawalDelayer
 	contractAbi abi.ABI
 }
 
 // NewWDelayerClient creates a new WDelayerClient
 func NewWDelayerClient(client *EthereumClient, address ethCommon.Address) (*WDelayerClient, error) {
 	contractAbi, err := abi.JSON(strings.NewReader(string(WithdrawalDelayer.WithdrawalDelayerABI)))
+	if err != nil {
+		return nil, err
+	}
+	wdelayer, err := WithdrawalDelayer.NewWithdrawalDelayer(address, client.Client())
 	if err != nil {
 		return nil, err
 	}
 	return &WDelayerClient{
 		client:      client,
 		address:     address,
-		gasLimit:    1000000, //nolint:gomnd
+		wdelayer:    wdelayer,
 		contractAbi: contractAbi,
 	}, nil
 }
 
 // WDelayerGetHermezGovernanceDAOAddress is the interface to call the smart contract function
-func (c *WDelayerClient) WDelayerGetHermezGovernanceDAOAddress() (*ethCommon.Address, error) {
-	var hermezGovernanceDAOAddress ethCommon.Address
+func (c *WDelayerClient) WDelayerGetHermezGovernanceDAOAddress() (hermezGovernanceDAOAddress *ethCommon.Address, err error) {
+	var _hermezGovernanceDAOAddress ethCommon.Address
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		wdelayer, err := WithdrawalDelayer.NewWithdrawalDelayer(c.address, ec)
-		if err != nil {
-			return err
-		}
-		hermezGovernanceDAOAddress, err = wdelayer.GetHermezGovernanceDAOAddress(nil)
+		_hermezGovernanceDAOAddress, err = c.wdelayer.GetHermezGovernanceDAOAddress(nil)
 		return err
 	}); err != nil {
 		return nil, err
 	}
-	return &hermezGovernanceDAOAddress, nil
+	return &_hermezGovernanceDAOAddress, nil
 }
 
 // WDelayerSetHermezGovernanceDAOAddress is the interface to call the smart contract function
-func (c *WDelayerClient) WDelayerSetHermezGovernanceDAOAddress(newAddress ethCommon.Address) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *WDelayerClient) WDelayerSetHermezGovernanceDAOAddress(newAddress ethCommon.Address) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
-			wdelayer, err := WithdrawalDelayer.NewWithdrawalDelayer(c.address, ec)
-			if err != nil {
-				return nil, err
-			}
-			return wdelayer.SetHermezGovernanceDAOAddress(auth, newAddress)
+			return c.wdelayer.SetHermezGovernanceDAOAddress(auth, newAddress)
 		},
 	); err != nil {
 		return nil, fmt.Errorf("Failed setting hermezGovernanceDAOAddress: %w", err)
@@ -190,33 +184,23 @@ return tx, nil
 }
 
 // WDelayerGetHermezKeeperAddress is the interface to call the smart contract function
-func (c *WDelayerClient) WDelayerGetHermezKeeperAddress() (*ethCommon.Address, error) {
-	var hermezKeeperAddress ethCommon.Address
+func (c *WDelayerClient) WDelayerGetHermezKeeperAddress() (hermezKeeperAddress *ethCommon.Address, err error) {
+	var _hermezKeeperAddress ethCommon.Address
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		wdelayer, err := WithdrawalDelayer.NewWithdrawalDelayer(c.address, ec)
-		if err != nil {
-			return err
-		}
-		hermezKeeperAddress, err = wdelayer.GetHermezKeeperAddress(nil)
+		_hermezKeeperAddress, err = c.wdelayer.GetHermezKeeperAddress(nil)
 		return err
 	}); err != nil {
 		return nil, err
 	}
-	return &hermezKeeperAddress, nil
+	return &_hermezKeeperAddress, nil
 }
 
 // WDelayerSetHermezKeeperAddress is the interface to call the smart contract function
-func (c *WDelayerClient) WDelayerSetHermezKeeperAddress(newAddress ethCommon.Address) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *WDelayerClient) WDelayerSetHermezKeeperAddress(newAddress ethCommon.Address) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
-			wdelayer, err := WithdrawalDelayer.NewWithdrawalDelayer(c.address, ec)
-			if err != nil {
-				return nil, err
-			}
-			return wdelayer.SetHermezKeeperAddress(auth, newAddress)
+			return c.wdelayer.SetHermezKeeperAddress(auth, newAddress)
 		},
 	); err != nil {
 		return nil, fmt.Errorf("Failed setting hermezKeeperAddress: %w", err)
@@ -225,33 +209,23 @@ return tx, nil
 }
 
 // WDelayerGetWhiteHackGroupAddress is the interface to call the smart contract function
-func (c *WDelayerClient) WDelayerGetWhiteHackGroupAddress() (*ethCommon.Address, error) {
-	var whiteHackGroupAddress ethCommon.Address
+func (c *WDelayerClient) WDelayerGetWhiteHackGroupAddress() (whiteHackGroupAddress *ethCommon.Address, err error) {
+	var _whiteHackGroupAddress ethCommon.Address
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		wdelayer, err := WithdrawalDelayer.NewWithdrawalDelayer(c.address, ec)
-		if err != nil {
-			return err
-		}
-		whiteHackGroupAddress, err = wdelayer.GetWhiteHackGroupAddress(nil)
+		_whiteHackGroupAddress, err = c.wdelayer.GetWhiteHackGroupAddress(nil)
 		return err
 	}); err != nil {
 		return nil, err
 	}
-	return &whiteHackGroupAddress, nil
+	return &_whiteHackGroupAddress, nil
 }
 
 // WDelayerSetWhiteHackGroupAddress is the interface to call the smart contract function
-func (c *WDelayerClient) WDelayerSetWhiteHackGroupAddress(newAddress ethCommon.Address) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *WDelayerClient) WDelayerSetWhiteHackGroupAddress(newAddress ethCommon.Address) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
-			wdelayer, err := WithdrawalDelayer.NewWithdrawalDelayer(c.address, ec)
-			if err != nil {
-				return nil, err
-			}
-			return wdelayer.SetWhiteHackGroupAddress(auth, newAddress)
+			return c.wdelayer.SetWhiteHackGroupAddress(auth, newAddress)
 		},
 	); err != nil {
 		return nil, fmt.Errorf("Failed setting whiteHackGroupAddress: %w", err)
@@ -260,14 +234,9 @@ return tx, nil
 }
 
 // WDelayerIsEmergencyMode is the interface to call the smart contract function
-func (c *WDelayerClient) WDelayerIsEmergencyMode() (bool, error) {
-	var ermergencyMode bool
+func (c *WDelayerClient) WDelayerIsEmergencyMode() (ermergencyMode bool, err error) {
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		wdelayer, err := WithdrawalDelayer.NewWithdrawalDelayer(c.address, ec)
-		if err != nil {
-			return err
-		}
-		ermergencyMode, err = wdelayer.IsEmergencyMode(nil)
+		ermergencyMode, err = c.wdelayer.IsEmergencyMode(nil)
 		return err
 	}); err != nil {
 		return false, err
@@ -276,14 +245,9 @@ return ermergencyMode, nil
 }
 
 // WDelayerGetWithdrawalDelay is the interface to call the smart contract function
-func (c *WDelayerClient) WDelayerGetWithdrawalDelay() (*big.Int, error) {
-	var withdrawalDelay *big.Int
+func (c *WDelayerClient) WDelayerGetWithdrawalDelay() (withdrawalDelay *big.Int, err error) {
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		wdelayer, err := WithdrawalDelayer.NewWithdrawalDelayer(c.address, ec)
-		if err != nil {
-			return err
-		}
-		withdrawalDelay, err = wdelayer.GetWithdrawalDelay(nil)
+		withdrawalDelay, err = c.wdelayer.GetWithdrawalDelay(nil)
 		return err
 	}); err != nil {
 		return nil, err
@@ -292,14 +256,9 @@ return withdrawalDelay, nil
 }
 
 // WDelayerGetEmergencyModeStartingTime is the interface to call the smart contract function
-func (c *WDelayerClient) WDelayerGetEmergencyModeStartingTime() (*big.Int, error) {
-	var emergencyModeStartingTime *big.Int
+func (c *WDelayerClient) WDelayerGetEmergencyModeStartingTime() (emergencyModeStartingTime *big.Int, err error) {
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		wdelayer, err := WithdrawalDelayer.NewWithdrawalDelayer(c.address, ec)
-		if err != nil {
-			return err
-		}
-		emergencyModeStartingTime, err = wdelayer.GetEmergencyModeStartingTime(nil)
+		emergencyModeStartingTime, err = c.wdelayer.GetEmergencyModeStartingTime(nil)
 		return err
 	}); err != nil {
 		return nil, err
@@ -308,17 +267,11 @@ return emergencyModeStartingTime, nil
 }
 
 // WDelayerEnableEmergencyMode is the interface to call the smart contract function
-func (c *WDelayerClient) WDelayerEnableEmergencyMode() (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *WDelayerClient) WDelayerEnableEmergencyMode() (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
-			wdelayer, err := WithdrawalDelayer.NewWithdrawalDelayer(c.address, ec)
-			if err != nil {
-				return nil, err
-			}
-			return wdelayer.EnableEmergencyMode(auth)
+			return c.wdelayer.EnableEmergencyMode(auth)
 		},
 	); err != nil {
 		return nil, fmt.Errorf("Failed setting enable emergency mode: %w", err)
@@ -327,17 +280,11 @@ return tx, nil
 }
 
 // WDelayerChangeWithdrawalDelay is the interface to call the smart contract function
-func (c *WDelayerClient) WDelayerChangeWithdrawalDelay(newWithdrawalDelay uint64) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *WDelayerClient) WDelayerChangeWithdrawalDelay(newWithdrawalDelay uint64) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
-			wdelayer, err := WithdrawalDelayer.NewWithdrawalDelayer(c.address, ec)
-			if err != nil {
-				return nil, err
-			}
-			return wdelayer.ChangeWithdrawalDelay(auth, newWithdrawalDelay)
+			return c.wdelayer.ChangeWithdrawalDelay(auth, newWithdrawalDelay)
 		},
 	); err != nil {
 		return nil, fmt.Errorf("Failed setting withdrawal delay: %w", err)
@@ -346,14 +293,9 @@ return tx, nil
 }
 
 // WDelayerDepositInfo is the interface to call the smart contract function
-func (c *WDelayerClient) WDelayerDepositInfo(owner, token ethCommon.Address) (DepositState, error) {
-	var depositInfo DepositState
+func (c *WDelayerClient) WDelayerDepositInfo(owner, token ethCommon.Address) (depositInfo DepositState, err error) {
 	if err := c.client.Call(func(ec *ethclient.Client) error {
-		wdelayer, err := WithdrawalDelayer.NewWithdrawalDelayer(c.address, ec)
-		if err != nil {
-			return err
-		}
-		amount, depositTimestamp, err := wdelayer.DepositInfo(nil, owner, token)
+		amount, depositTimestamp, err := c.wdelayer.DepositInfo(nil, owner, token)
 		depositInfo.Amount = amount
 		depositInfo.DepositTimestamp = depositTimestamp
 		return err
@@ -364,17 +306,11 @@ return depositInfo, nil
 }
 
 // WDelayerDeposit is the interface to call the smart contract function
-func (c *WDelayerClient) WDelayerDeposit(owner, token ethCommon.Address, amount *big.Int) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *WDelayerClient) WDelayerDeposit(owner, token ethCommon.Address, amount *big.Int) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
-			wdelayer, err := WithdrawalDelayer.NewWithdrawalDelayer(c.address, ec)
-			if err != nil {
-				return nil, err
-			}
-			return wdelayer.Deposit(auth, owner, token, amount)
+			return c.wdelayer.Deposit(auth, owner, token, amount)
 		},
 	); err != nil {
 		return nil, fmt.Errorf("Failed deposit: %w", err)
@@ -383,17 +319,11 @@ return tx, nil
 }
 
 // WDelayerWithdrawal is the interface to call the smart contract function
-func (c *WDelayerClient) WDelayerWithdrawal(owner, token ethCommon.Address) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *WDelayerClient) WDelayerWithdrawal(owner, token ethCommon.Address) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
-			wdelayer, err := WithdrawalDelayer.NewWithdrawalDelayer(c.address, ec)
-			if err != nil {
-				return nil, err
-			}
-			return wdelayer.Withdrawal(auth, owner, token)
+			return c.wdelayer.Withdrawal(auth, owner, token)
 		},
 	); err != nil {
 		return nil, fmt.Errorf("Failed withdrawal: %w", err)
@@ -402,17 +332,11 @@ return tx, nil
 }
 
 // WDelayerEscapeHatchWithdrawal is the interface to call the smart contract function
-func (c *WDelayerClient) WDelayerEscapeHatchWithdrawal(to, token ethCommon.Address, amount *big.Int) (*types.Transaction, error) {
-	var tx *types.Transaction
-	var err error
+func (c *WDelayerClient) WDelayerEscapeHatchWithdrawal(to, token ethCommon.Address, amount *big.Int) (tx *types.Transaction, err error) {
 	if tx, err = c.client.CallAuth(
-		c.gasLimit,
+		0,
 		func(ec *ethclient.Client, auth *bind.TransactOpts) (*types.Transaction, error) {
-			wdelayer, err := WithdrawalDelayer.NewWithdrawalDelayer(c.address, ec)
-			if err != nil {
-				return nil, err
-			}
-			return wdelayer.EscapeHatchWithdrawal(auth, to, token, amount)
+			return c.wdelayer.EscapeHatchWithdrawal(auth, to, token, amount)
 		},
 	); err != nil {
 		return nil, fmt.Errorf("Failed escapeHatchWithdrawal: %w", err)

@@ -82,7 +82,10 @@ ethClient, err := ethclient.Dial(cfg.Web3.URL)
 	if err != nil {
 		return nil, err
 	}
-	client := eth.NewClient(ethClient, nil, nil, nil)
+	client, err := eth.NewClient(ethClient, nil, nil, nil)
+	if err != nil {
+		return nil, err
+	}
 
 	sync, err := synchronizer.NewSynchronizer(client, historyDB, stateDB)
 	if err != nil {

@@ -383,7 +383,7 @@ batchData := historydb.NewBatchData()
 		position := 0
 
 		// Get the input for each Tx
-		forgeBatchArgs, err := s.ethClient.RollupForgeBatchArgs(evtForgeBatch.EthTxHash)
+		forgeBatchArgs, sender, err := s.ethClient.RollupForgeBatchArgs(evtForgeBatch.EthTxHash)
 		if err != nil {
 			return nil, err
 		}
@@ -467,7 +467,7 @@ // Get Batch information
 		batch := &common.Batch{
 			BatchNum:    common.BatchNum(evtForgeBatch.BatchNum),
 			EthBlockNum: blockNum,
-			// ForgerAddr: , TODO: Get it from ethClient -> Add ForgerAddr to RollupEventForgeBatch
+			ForgerAddr:  *sender,
 			// CollectedFees: , TODO: Clarify where to get them if they are still needed
 			StateRoot:     common.Hash(forgeBatchArgs.NewStRoot.Bytes()),
 			NumAccounts:   numAccounts,
@@ -582,11 +582,6 @@ func getL1UserTx(eventsL1UserTx []eth.RollupEventL1UserTx, blockNum int64) ([]common.L1Tx, error) {
 	l1Txs := make([]common.L1Tx, 0)
 
 	for _, evtL1UserTx := range eventsL1UserTx {
-		// Fill aditional Tx fields
-		toForge := evtL1UserTx.ToForgeL1TxsNum
-		evtL1UserTx.L1UserTx.ToForgeL1TxsNum = &toForge
-		evtL1UserTx.L1UserTx.Position = evtL1UserTx.Position
-		evtL1UserTx.L1UserTx.UserOrigin = true
 		evtL1UserTx.L1UserTx.EthBlockNum = blockNum
 		nL1Tx, err := common.NewL1Tx(&evtL1UserTx.L1UserTx)
 		if err != nil {

@@ -57,7 +57,7 @@ require.Nil(t, err)
 
 	blocks, err := s.historyDB.GetBlocks(0, 9999)
 	require.Nil(t, err)
-	assert.Equal(t, int64(0), blocks[0].EthBlockNum)
+	assert.Equal(t, int64(1), blocks[0].EthBlockNum)
 
 	// TODO once transakcio is completed
 	/*

@@ -10,6 +10,7 @@ "reflect"
 	"sync"
 	"time"
 
+	"github.com/ethereum/go-ethereum"
 	ethCommon "github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/hermeznetwork/hermez-node/common"
@@ -225,7 +226,9 @@ AuctionVariables *eth.AuctionVariables
 	VerifyProof      bool
 }
 
-// NewClientSetupExample returns a ClientSetup example with hardcoded realistic values.
+// NewClientSetupExample returns a ClientSetup example with hardcoded realistic
+// values.  With this setup, the rollup genesis will be block 1, and block 0
+// and 1 will be premined.
 //nolint:gomnd
 func NewClientSetupExample() *ClientSetup {
 	// rfield, ok := new(big.Int).SetString("21888242871839275222246405745257275088548364400416034343698204186575808495617", 10)
@@ -259,7 +262,7 @@ }
 	auctionConstants := &eth.AuctionConstants{
 		BlocksPerSlot:         40,
 		InitialMinimalBidding: initialMinimalBidding,
-		GenesisBlockNum:       0,
+		GenesisBlockNum:       1,
 		GovernanceAddress:     governanceAddress,
 		TokenHEZ:              tokenHEZ,
 		HermezRollup:          ethCommon.HexToAddress("0x474B6e29852257491cf283EfB1A9C61eBFe48369"),
@@ -296,6 +299,11 @@ // 	blockNum  int64
 // 	blockHash ethCommon.Hash
 // }
 
+type batch struct {
+	ForgeBatchArgs eth.RollupForgeBatchArgs
+	Sender         ethCommon.Address
+}
+
 // Client implements the eth.ClientInterface interface, allowing to manipulate the
 // values for testing, working with deterministic results.
 type Client struct {
@@ -311,8 +319,8 @@ maxBlockNum int64 // highest block num calculated
 	timer       Timer
 	hasher      hasher
 
-	forgeBatchArgsPending map[ethCommon.Hash]*eth.RollupForgeBatchArgs
-	forgeBatchArgs        map[ethCommon.Hash]*eth.RollupForgeBatchArgs
+	forgeBatchArgsPending map[ethCommon.Hash]*batch
+	forgeBatchArgs        map[ethCommon.Hash]*batch
 }
 
 // NewClient returns a new test Client that implements the eth.IClient
@@ -326,7 +334,7 @@ // Add ethereum genesis block
 	mapL1TxQueue := make(map[int64]*eth.QueueStruct)
 	mapL1TxQueue[0] = eth.NewQueueStruct()
 	mapL1TxQueue[1] = eth.NewQueueStruct()
-	blockCurrent := Block{
+	blockCurrent := &Block{
 		Rollup: &RollupBlock{
 			State: eth.RollupState{
 				StateRoot:        big.NewInt(0),
@@ -367,11 +375,11 @@ },
 	}
 	blockCurrent.Rollup.Eth = blockCurrent.Eth
 	blockCurrent.Auction.Eth = blockCurrent.Eth
-	blocks[blockNum] = &blockCurrent
+	blocks[blockNum] = blockCurrent
 	blockNext := blockCurrent.Next()
 	blocks[blockNum+1] = blockNext
 
-	return &Client{
+	c := Client{
 		rw:                    &sync.RWMutex{},
 		log:                   l,
 		addr:                  addr,
@@ -380,9 +388,17 @@ auctionConstants:      setup.AuctionConstants,
 		blocks:                blocks,
 		timer:                 timer,
 		hasher:                hasher,
-		forgeBatchArgsPending: make(map[ethCommon.Hash]*eth.RollupForgeBatchArgs),
-		forgeBatchArgs:        make(map[ethCommon.Hash]*eth.RollupForgeBatchArgs),
+		forgeBatchArgsPending: make(map[ethCommon.Hash]*batch),
+		forgeBatchArgs:        make(map[ethCommon.Hash]*batch),
+		blockNum:              blockNum,
+		maxBlockNum:           blockNum,
+	}
+
+	for i := int64(1); i < setup.AuctionConstants.GenesisBlockNum+1; i++ {
+		c.CtlMineBlock()
 	}
+
+	return &c
 }
 
 //
@@ -452,7 +468,7 @@ blockCurrent.Eth.Hash = c.hasher.Next()
 	for ethTxHash, forgeBatchArgs := range c.forgeBatchArgsPending {
 		c.forgeBatchArgs[ethTxHash] = forgeBatchArgs
 	}
-	c.forgeBatchArgsPending = make(map[ethCommon.Hash]*eth.RollupForgeBatchArgs)
+	c.forgeBatchArgsPending = make(map[ethCommon.Hash]*batch)
 
 	blockNext := blockCurrent.Next()
 	c.blocks[c.blockNum+1] = blockNext
@@ -552,10 +568,10 @@ func (c *Client) EthBlockByNumber(ctx context.Context, blockNum int64) (*common.Block, error) {
 	c.rw.RLock()
 	defer c.rw.RUnlock()
 
-	block, ok := c.blocks[blockNum]
-	if !ok {
-		return nil, fmt.Errorf("block not found")
+	if blockNum > c.blockNum {
+		return nil, ethereum.NotFound
 	}
+	block := c.blocks[blockNum]
 	return &common.Block{
 		EthBlockNum: blockNum,
 		Timestamp:   time.Unix(block.Eth.Time, 0),
@@ -579,9 +595,54 @@ // Rollup
 //
 
 // CtlAddL1TxUser adds an L1TxUser to the L1UserTxs queue of the Rollup
-func (c *Client) CtlAddL1TxUser(l1Tx *common.L1Tx) {
+// func (c *Client) CtlAddL1TxUser(l1Tx *common.L1Tx) {
+// 	c.rw.Lock()
+// 	defer c.rw.Unlock()
+//
+// 	nextBlock := c.nextBlock()
+// 	r := nextBlock.Rollup
+// 	queue := r.State.MapL1TxQueue[r.State.LastToForgeL1TxsNum]
+// 	if len(queue.L1TxQueue) >= eth.RollupConstMaxL1UserTx {
+// 		r.State.LastToForgeL1TxsNum++
+// 		r.State.MapL1TxQueue[r.State.LastToForgeL1TxsNum] = eth.NewQueueStruct()
+// 		queue = r.State.MapL1TxQueue[r.State.LastToForgeL1TxsNum]
+// 	}
+// 	if int64(l1Tx.FromIdx) > r.State.CurrentIdx {
+// 		panic("l1Tx.FromIdx > r.State.CurrentIdx")
+// 	}
+// 	if int(l1Tx.TokenID)+1 > len(r.State.TokenList) {
+// 		panic("l1Tx.TokenID + 1 > len(r.State.TokenList)")
+// 	}
+// 	queue.L1TxQueue = append(queue.L1TxQueue, *l1Tx)
+// 	r.Events.L1UserTx = append(r.Events.L1UserTx, eth.RollupEventL1UserTx{
+// 		L1Tx:            *l1Tx,
+// 		ToForgeL1TxsNum: r.State.LastToForgeL1TxsNum,
+// 		Position:        len(queue.L1TxQueue) - 1,
+// 	})
+// }
+
+// RollupL1UserTxERC20ETH sends an L1UserTx to the Rollup.
+func (c *Client) RollupL1UserTxERC20ETH(
+	fromBJJ *babyjub.PublicKey,
+	fromIdx int64,
+	loadAmount *big.Int,
+	amount *big.Int,
+	tokenID uint32,
+	toIdx int64,
+) (tx *types.Transaction, err error) {
 	c.rw.Lock()
 	defer c.rw.Unlock()
+	cpy := c.nextBlock().copy()
+	defer func() { c.revertIfErr(err, cpy) }()
+
+	_, err = common.NewFloat16(amount)
+	if err != nil {
+		return nil, err
+	}
+	_, err = common.NewFloat16(loadAmount)
+	if err != nil {
+		return nil, err
+	}
 
 	nextBlock := c.nextBlock()
 	r := nextBlock.Rollup
@@ -591,24 +652,34 @@ r.State.LastToForgeL1TxsNum++
 		r.State.MapL1TxQueue[r.State.LastToForgeL1TxsNum] = eth.NewQueueStruct()
 		queue = r.State.MapL1TxQueue[r.State.LastToForgeL1TxsNum]
 	}
-	if int64(l1Tx.FromIdx) > r.State.CurrentIdx {
+	if fromIdx > r.State.CurrentIdx {
 		panic("l1Tx.FromIdx > r.State.CurrentIdx")
 	}
-	if int(l1Tx.TokenID)+1 > len(r.State.TokenList) {
+	if int(tokenID)+1 > len(r.State.TokenList) {
 		panic("l1Tx.TokenID + 1 > len(r.State.TokenList)")
 	}
-	queue.L1TxQueue = append(queue.L1TxQueue, *l1Tx)
-	r.Events.L1UserTx = append(r.Events.L1UserTx, eth.RollupEventL1UserTx{
-		L1UserTx:        *l1Tx,
-		ToForgeL1TxsNum: r.State.LastToForgeL1TxsNum,
+	toForgeL1TxsNum := r.State.LastToForgeL1TxsNum
+	l1Tx, err := common.NewL1Tx(&common.L1Tx{
+		FromIdx:         common.Idx(fromIdx),
+		FromEthAddr:     *c.addr,
+		FromBJJ:         fromBJJ,
+		Amount:          amount,
+		LoadAmount:      loadAmount,
+		TokenID:         common.TokenID(tokenID),
+		ToIdx:           common.Idx(toIdx),
+		ToForgeL1TxsNum: &toForgeL1TxsNum,
 		Position:        len(queue.L1TxQueue) - 1,
+		UserOrigin:      true,
 	})
-}
+	if err != nil {
+		return nil, err
+	}
 
-// RollupL1UserTxERC20ETH is the interface to call the smart contract function
-func (c *Client) RollupL1UserTxERC20ETH(fromBJJ *babyjub.PublicKey, fromIdx int64, loadAmount *big.Int, amount *big.Int, tokenID uint32, toIdx int64) (*types.Transaction, error) {
-	log.Error("TODO")
-	return nil, errTODO
+	queue.L1TxQueue = append(queue.L1TxQueue, *l1Tx)
+	r.Events.L1UserTx = append(r.Events.L1UserTx, eth.RollupEventL1UserTx{
+		L1UserTx: *l1Tx,
+	})
+	return r.addTransaction(newTransaction("l1UserTxERC20ETH", l1Tx)), nil
 }
 
 // RollupL1UserTxERC777 is the interface to call the smart contract function
@@ -710,7 +781,7 @@ r.State.MapL1TxQueue[r.State.LastToForgeL1TxsNum] = eth.NewQueueStruct()
 		}
 	}
 	ethTx := r.addTransaction(newTransaction("forgebatch", args))
-	c.forgeBatchArgsPending[ethTx.Hash()] = args
+	c.forgeBatchArgsPending[ethTx.Hash()] = &batch{*args, *c.addr}
 	r.Events.ForgeBatch = append(r.Events.ForgeBatch, eth.RollupEventForgeBatch{
 		BatchNum:  int64(len(r.State.ExitRoots)),
 		EthTxHash: ethTx.Hash(),
@@ -820,15 +891,15 @@ return &block.Rollup.Events, &block.Eth.Hash, nil
 }
 
 // RollupForgeBatchArgs returns the arguments used in a ForgeBatch call in the Rollup Smart Contract in the given transaction
-func (c *Client) RollupForgeBatchArgs(ethTxHash ethCommon.Hash) (*eth.RollupForgeBatchArgs, error) {
+func (c *Client) RollupForgeBatchArgs(ethTxHash ethCommon.Hash) (*eth.RollupForgeBatchArgs, *ethCommon.Address, error) {
 	c.rw.RLock()
 	defer c.rw.RUnlock()
 
-	forgeBatchArgs, ok := c.forgeBatchArgs[ethTxHash]
+	batch, ok := c.forgeBatchArgs[ethTxHash]
 	if !ok {
-		return nil, fmt.Errorf("transaction not found")
+		return nil, nil, fmt.Errorf("transaction not found")
 	}
-	return forgeBatchArgs, nil
+	return &batch.ForgeBatchArgs, &batch.Sender, nil
 }
 
 //

@@ -42,21 +42,21 @@ clientSetup := NewClientSetupExample()
 	c := NewClient(true, &timer, &ethCommon.Address{}, clientSetup)
 	blockNum, err := c.EthCurrentBlock()
 	require.Nil(t, err)
-	assert.Equal(t, int64(0), blockNum)
+	assert.Equal(t, int64(1), blockNum)
 
 	block, err := c.EthBlockByNumber(context.TODO(), 0)
 	require.Nil(t, err)
 	assert.Equal(t, int64(0), block.EthBlockNum)
 	assert.Equal(t, time.Unix(0, 0), block.Timestamp)
 	assert.Equal(t, "0x0000000000000000000000000000000000000000000000000000000000000000", block.Hash.Hex())
-	assert.Equal(t, int64(0), c.blockNum)
 
 	// Mine some empty blocks
 
-	c.CtlMineBlock()
 	assert.Equal(t, int64(1), c.blockNum)
 	c.CtlMineBlock()
 	assert.Equal(t, int64(2), c.blockNum)
+	c.CtlMineBlock()
+	assert.Equal(t, int64(3), c.blockNum)
 
 	block, err = c.EthBlockByNumber(context.TODO(), 2)
 	require.Nil(t, err)
@@ -154,14 +154,17 @@ const N = 16
 	var keys [N]*keys
 	for i := 0; i < N; i++ {
 		keys[i] = genKeys(int64(i))
-		l1UserTx := common.L1Tx{
+		tx := common.L1Tx{
 			FromIdx:     0,
 			FromEthAddr: keys[i].Addr,
 			FromBJJ:     keys[i].BJJPublicKey,
 			TokenID:     common.TokenID(0),
+			Amount:      big.NewInt(0),
 			LoadAmount:  big.NewInt(10 + int64(i)),
 		}
-		c.CtlAddL1TxUser(&l1UserTx)
+		_, err := c.RollupL1UserTxERC20ETH(tx.FromBJJ, int64(tx.FromIdx), tx.LoadAmount,
+			tx.Amount, uint32(tx.TokenID), int64(tx.ToIdx))
+		require.Nil(t, err)
 	}
 	c.CtlMineBlock()
 
@@ -231,8 +234,9 @@ require.Nil(t, err)
 	rollupEvents, _, err = c.RollupEventsByBlock(blockNum)
 	require.Nil(t, err)
 
-	rollupForgeBatchArgs1, err := c.RollupForgeBatchArgs(rollupEvents.ForgeBatch[0].EthTxHash)
+	rollupForgeBatchArgs1, sender, err := c.RollupForgeBatchArgs(rollupEvents.ForgeBatch[0].EthTxHash)
 	require.Nil(t, err)
+	assert.Equal(t, *c.addr, *sender)
 	assert.Equal(t, rollupForgeBatchArgs0, rollupForgeBatchArgs1)
 }