SDA pin become low in I2C communication.

Amtech

Other Parts Discussed in Thread: TMS320F28069

Dear Sir,

We are using piccolo series DSP TMS320F28069 and using I²C communication with 16k EEPROM (24LC128, Microchip). We face some problem during power off and on condition (one in out of ten trials). In this condition SDA pin become low. Below picture for detail. In this picture red shows SDA pin of DSP and blue shows XRS pin of DSP. Where shows XRS pin shows multiple time reset where SDA pin become low and low.

For this reason I2C communication cannot establish. We try to I²C reset in power on condition but can’t do. What can we do in this condition?

Waiting for prompt reply.

Regards,

Suprit

over 12 years ago

0 Adam Dunhoft over 12 years ago

TI__Expert 7885 points

Hi Suprit,

Sorry, I am unclear of what the issue is here. Is the problem that the device is continuously resetting or is the problem that the SDA pin never goes back high after going into reset?

Regards,

Adam

0 Amtech over 12 years ago in reply to Adam Dunhoft

Genius 4585 points

Dear Adam,

Problem is SDA pin never goes back high after going in to reset.

Regards,

Suprit

0 Adam Dunhoft over 12 years ago in reply to Amtech

TI__Expert 7885 points

Suprit,

It looks like XRSn is toggling, which may be caused by the watchdog. Does this toggling only happen 1 out of 10 times or do you always see this?

Regards,

Adam

0 Amtech over 12 years ago in reply to Adam Dunhoft

Genius 4585 points

Adam,

I am not using watchdog in my application and i am not able to use due to application limitation.

XRS pin toggling every time when power off.

but SDA pin become low in 1 out of 10 times. this time i power supply off and on condition.

Regards,

Suprit

0 Adam Haun over 12 years ago in reply to Amtech

TI__Expert 8950 points

Suprit,

Do you have the correct pull-ups on SDA and SCL? Are you sure that the MCU is pulling SDA low and not the EEPROM? Have you checked the GPIO registers to confirm that the I2C module has control of the pin? What happens to SCL when SDA gets stuck?

Thanks,

0 Amtech over 12 years ago in reply to Adam Haun

Genius 4585 points

Adam,

-Pull-up are OK.

-Yes, i am sure, MCU is pulling SDA low and not the EEPROM,

-GPIO registers checked and OK.

- SCL pin in high state(3.3V) when SDA stuck.

Thanks,

Suprit

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SDA pin become low in I2C communication.