IO-EXPANDER-EVM: Cannot communicate with TCA6424A over I2C

Zekeriya Bora Sunamak

Part Number: IO-EXPANDER-EVM
Other Parts Discussed in Thread: TCA6416A, USB2ANY, TCA6424, TCA6416, TCA9539, TCA6424A

I have IO Expander EVM board with TCA6416A installed. It's address pin is pulled up by design, so the address is 0x21. I send a dummy data to it, like 0x00, it does not respond, a NACK bit is recieved. I tried other possible slave addresses, pulled that address line to ground with a jumper, and shifted both options to one bit right and left in case of need. Still, I cannot communicate with it. I was using F2803x MCU as master, but for speed and debug purposes, I have a USB2ANY, I'm trying to send data from that.

I can communicate with the other IO expander on the EVM board however, its TCA6424. It sends ACK bit.

What should I do? I run out of options.

Thanks

over 2 years ago

0 Tyler Townsend over 2 years ago

TI__Mastermind 47378 points

Hi Zekeriya,

Can you show scope captures of the I2C bus showing the NACK bit?

Are you using the pre-existing TCA6416 on the PCB, or did you solder on the TCA6416A to replace the non-A version?

Regards,

Tyler

0 Clemens Ladisch over 2 years ago

Guru 316690 points

I²C accesses to the TCA6424 and TCA6416 should work in exactly the same way, except for the address (0x23 vs. 0x21). So if only one of them works, this looks like a hardware problem. Check for soldering errors (dry joints or shorts), or try to replace the chip.

0 Zekeriya Bora Sunamak over 2 years ago in reply to Tyler Townsend

Prodigy 30 points

Here's the scope output, at 100kHz.

I tried with grounding the address pin,

one bit shifted to right/left in both cases, all are the same as this one.

I did not altered the board, however, noticed now, It says "PW539 0BKG4 A8FP" on the chip.

Is it possible that it shipped with a different chip?

Thanks, and sorry for the late response.
Scope output of I2C write to address 0x21

0 Zekeriya Bora Sunamak over 2 years ago in reply to Clemens Ladisch

Prodigy 30 points

I will check and post back again. Thanks.

+1 Clemens Ladisch over 2 years ago in reply to Zekeriya Bora Sunamak

Guru 316690 points

PW539 definitely is the TCA9539, which has address 11101xx.

The EVM documentation says: "The TCA6424A and TCA9539 come installed on the board." Where did you get the information that there would be a TCA6416A?

0 Zekeriya Bora Sunamak over 2 years ago in reply to Clemens Ladisch

Prodigy 30 points

On EVM's datasheet's schematic, the U2 chip is TCA6416A, so I thought that was it. I missed it due to the high workload going on at the moment, I felt a bit silly. Thanks a lot.

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IO-EXPANDER-EVM: Cannot communicate with TCA6424A over I2C