TMS320F2800156-Q1: I2C not working on the smallest package

Emil Yordanov

Part Number: TMS320F2800156-Q1
Other Parts Discussed in Thread: SYSCONFIG

Hello,

We're facing an issue with I2C not working on the smallest package of TMS320F2800156-Q1, while the same project works correctly on the F280015x controlCARD.

What works:
- Same application code and I2C driver
- I2C traffic confirmed with logic analyzer on the controlCARD
- SysConfig validated for the controlCARD pinout

What fails:
- On the production board (smallest package), no I2C activity is observed on SDA/SCL
- Logic analyzer shows no toggling at all

Key difference:
- On the small package, the selected I2C pins are shared with full JTAG TDI/TDO
- Production board uses 2-wire JTAG
- TDI/TDO pins are not connected to the JTAG header and are physically routed only to I2C (SDA/SCL)

Attached is the SysConfig (.syscfg renamed as TXT) used on the production board.

Please look into the configuration file ac2000.syscfg.txt nd advise us on possible solutions. Let us know if you require any aditional information.

Thanks in advance for your help.

7 months ago

0 Aishwarya Rajesh 7 months ago

TI__Mastermind 20695 points

Emil,

It is fine to repurpose TDI/TDO as GPIOs. Can you confirm if "the internal pullup should be enabled or an external pullup added on the board to avoid a floating GPIO input."?

Best Regards,

Aishwarya

0 Emil Yordanov 6 months ago in reply to Aishwarya Rajesh

Prodigy 100 points

Hello Aishwarya,

Yes, that was the first thing we checked. We have an external 1.2 kΩ pull‑up to 3V3 on pins 17 and 19 on TMS320F2800156-Q1 in VQFN32. We also tried configuring the internal pull‑ups. The result is the same in both cases — there is no activity on the bus.

0 Aishwarya Rajesh 6 months ago

TI__Mastermind 20695 points

Emil,

Thanks for confirming, let me try this on my end and get back to you by the end of the week.

Beat Regards,

Aishwarya

0 Aishwarya Rajesh 6 months ago

TI__Mastermind 20695 points

Emil,

Your SysConfig settings look right to me. Can the user try an I2C loopback test using I2C EX #1 with those same GPIOs? In the meantime, I will try to find a 32-pin F280015x to reproduce the issue on my end.

Best Regards,

Aishwarya

0 Emil Yordanov 6 months ago in reply to Aishwarya Rajesh

Prodigy 20 points

Yes, it would be optimal if we have the same hardware.Thank you for your effort. We continue the investigation on our side.
We have successfully run the Internal Loopback I2C example. This means that the there is successful initialization of the module. However when trying to establish communication with an external device the physical pins stay constantly HIGH and no communication is flowing. Could you please advise us on any specifics of the configuration or any other missing piece that would aid us with the physical layer issue?

0 Aishwarya Rajesh 6 months ago

TI__Mastermind 20695 points

Emil,

That is good to hear. I will keep looking at it my end, sorry the delay as I haven't been able to find a board to replicate the issue.

Best Regards,

Aishwarya

+1 Aishwarya Rajesh 6 months ago

TI__Mastermind 20695 points

Emil,

I was able to successfully run the i2c_ex3_external_loopback example with I2CA (GPIO35, GPIO37) and I2CB (GPIO28, GPIO3) on a 32-pin F280015x. For quick testing, I didn't port the example to use SysConfig, but this should still be a helpful reference.

0675.i2c_ex3_external_loopback.zip

Best Regards,

Aishwarya

C2000™︎ microcontrollers

C2000 microcontrollers forum

TMS320F2800156-Q1: I2C not working on the smallest package