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PCF8574 - Busy signal when

Joseph Kissell
Prodigy 60 points
Other Parts Discussed in Thread: PCF8574

We have 4 identical boards using the same firmware. However, 2 of the boards fail to communicate with our PCF8574 chips.

 

I’ve debugged the code down to this line of code: I2C1_C1 |= I2C_C1_IICEN_MASK;

All I2C registers are identical up to this line of code.

 

This line “Enables I2C module operation”. On the two boards that work correctly, this bit is set as expected. On the two boards that fail, this bit gets set, but ALSO the Status Register’s Busy flag gets set. 

I feel that this busy flag is trying to tell me something, but I'm not sure how to interpret it in this case.

  • 0
    TI__Guru 64480 points

    Have you figured out the issue you were encountering?

    The above code appears to be associated with the processor that you are using rather than the PCF8574 device.

  • 0 in reply to BrandonAzbell
    Prodigy 60 points

    Yes, I worked though this issue already.

    I observed that the issue was only present when I quickly power-cycled the unit, the capacitance on the chips' power supply kept the chip powered-up, but the power-cycle generate a pulse on the SCL and SDA lines. So, the chip thought it was mid transmission (BUSY). When the issue occurred, I verified that the bus returned to a NON-busy state after I pulsed out more clock signals.