I’m having a problem getting I2C running with a PIC32MX795F512L. It was not acknowledging the address byte being sent out, so I put a logic analyzer on SDA and SCL and got the trace shown below:
The two excursions on the SCL line are the only ones that occur. So I don’t understand why there are only two, instead of one per bit plus the start and stop conditions. This is obviously why I never see any acknowledgment.
Also, SCL is low all of the time before these sequence starts, and I expected it to be high and then go low with SDA high to indicate a start condition. I have checked that I have pullups on both SCL and SDA.
The code I am using is straight out of Microchip’s I2C example code. Here is the relevant part:
// Start the transfer to write data to the EEPROM
if( !StartTransfer(FALSE) )
{
while(1);
}
// Transmit all data
Index = 0;
while( Success && (Index < DataSz) )
{
// Transmit a byte
if (TransmitOneByte(i2cData[Index]))
{
// Advance to the next byte
Index++;
// Verify that the byte was acknowledged
if(!I2CByteWasAcknowledged(EEPROM_I2C_BUS))
{
DBPRINTF("Error: Sent byte was not acknowledged\n");
Success = FALSE;
}
else
{
Success = TRUE;
}
}
else
{
Success = FALSE;
}
}
// End the transfer (hang here if an error occured)
StopTransfer();
if(!Success)
{
while(1);
}
It gets to the I2CByteWasAcknowledged call and fails. Anyone have any pointers on getting I2C on a PIC32 to work with the Peripheral Library code?
