Pedro , to read back the bytes sent just tranfer the content from RxBuffer int TxBuffer in the slave.

Code:
Select Case RxBuffer[0]
TxBuffer[0]=RxBuffer[0]
TxBuffer[1]=RxBuffer[1]
TxBuffer[2]=RxBuffer[2]
TxBuffer[3]=RxBuffer[3]
Case 4
High LEDT
Case 10
Low LEDT
Case 56
do anything
Case 21
do anything
End Select
From master just use this code:

Code:
I2CRead SDA,SCL,I2Caddress,[str YourBuffer\4], bogus
You will find the four bytes into the array YourBuffer

Al.