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Original question:

TCA9555: TCA9555

TCA9555: TCA9555

Andrei Anikin
Prodigy 40 points
Part Number: TCA9555

Hi team!

I have yet one question about TCA9555.

Now I programming Atmega 2561 connected with TCA9555 throw TWI (I2C) bus.

TCA9555 works for input. All works fine - I read input pins, its state change when i connect its to ground. But one feature exists: when i connect pin P07 with ground - TWI protocol hangs.

What wrong ?

Sincerely yours,

Andrei

  • 0
    TI__Guru 62920 points

    HI Andrei,

    That sounds strange.  Is P07 configured as an input?  If so, is it able to be read normally but not when tied to ground?  How is ground connected - is it the same ground as the one shared by the chip?  (Perhaps it would be good to verify the pin voltages with respect to the IC ground just to make sure.)  Are you able to successfully pull other ports low without hanging up the protocol?

    Max

  • 0 in reply to Miguel Robertson
    Prodigy 40 points

    Hi Max,

    I agree with you that sounds strange. But...

    P07 configured as an input - i wrote nothing into Polarity inversion port (initially it has been filled 0 - as input). Ground is the one shared by the chip. Other pins has normal behavior and has no differences from P07. More over, i've perform test with inverse polarity P07. Situation with hanging TWI (I2C) repeated but when P07 pulled up to top level !

    So i think, that problem is that value from P07 go to the SDA first in READ operation (MSB). May be it interference with REPEATED START condition from master ?

    Andrei

  • 0 in reply to Andrei Anikin
    TI__Guru 62920 points

    Andrei,

    That's an interesting thought.  Do you see similar issues with P17?  I'd expect that to behave similarly since it would be the MSB when reading input port 2.  Is it possible to probe the SDA/SCL lines to see what is happening after P07 goes low?  I guess this sends an interrupt to the processor that would then try to go read the port values, so we could see if that read operation gets corrupted somehow.

    Max

  • 0 in reply to Miguel Robertson
    TI__Guru 74252 points

    Hey Andrei,

    I was just following up on this thread, were you able to address your initial issue from this thread? Or were there any other questions you had?

    Regards,