Posted on May 17, 2011 at 13:13I've got a strange problem with I2C with DMA transfers.
If I'm transmitting to a slave, on the DMA_InitStructure.DMA_BufferSize, I have to put always a value 1byte higher than what I want to write. This doesn't happen if receiving from slave. It's wierd because it's like DMA1_FLAG_TC4 is set before transfer is complete, or something similar..
So, for example, if I set DMA_InitStructure4.DMA_BufferSize = 5, it will only read 4 bytes (checked on the oscilloscope).
Does somebody know a reason for this? I'm having problems accessing an EEPROM, and this behavior is related somehow.
Following you will find the code I'm using.
-> command I2C2_Master_BufferWrite(Buffer, TxLgth);
void I2C2_Master_BufferWrite(u8* pBuffer, u8 NumByteToWrite){
I2C2_TXOK = false;
DMA_InitStructure4.DMA_MemoryBaseAddr = (u32)pBuffer;
DMA_InitStructure4.DMA_BufferSize = (u32)NumByteToWrite
+1;
KERN_DMAChannel4Configuration();
I2C_ITConfig(I2C2, I2C_IT_EVT | I2C_IT_ERR, ENABLE);
I2C_DMACmd(I2C2, ENABLE);
/* Enable the DMA Channel4 Transfer Complete IT */
DMA_ITConfig(DMA1_Channel4, DMA_IT_TC, ENABLE);
/* Generate the START */
I2C_GenerateSTART(I2C2, ENABLE);
}
void I2C2_Master_BufferRead(u8* pBuffer, u8 NumByteToRead){
I2C2_RXOK = false;
DMA_InitStructure5.DMA_MemoryBaseAddr = (u32)pBuffer;
DMA_InitStructure5.DMA_BufferSize = (u32)NumByteToRead;
KERN_DMAChannel5Configuration();
I2C_ITConfig(I2C2, I2C_IT_EVT | I2C_IT_ERR, ENABLE);
/* Set Last bit to have a NACK on the last received byte */
I2C_DMALastTransferCmd(I2C2, ENABLE);
I2C_DMACmd(I2C2, ENABLE);
/* Enable the DMA Channel5 Transfer Complete IT */
DMA_ITConfig(DMA1_Channel5, DMA_IT_TC, ENABLE);
/* Generate the START */
I2C_GenerateSTART(I2C2, ENABLE);
}
Interrupt servicing :
void DMA1_Channel4_IRQHandler(void)
{
/* I2C2 TX */
DMA_Cmd(DMA1_Channel4, DISABLE);
DMA_ClearFlag(DMA1_FLAG_TC4);
I2C_GenerateSTOP(I2C2, ENABLE);
I2C2_TXOK = true;
}
Thanks!
J
[ This message was edited by: jvaque on 03-06-2009 09:53 ]
