ChibiOS Free Embedded RTOS

Posted: **Mon Jun 03, 2019 3:09 pm**

Hi all,

I have a custom board on which I have an I2C chip connected on PB10/11 (I2C2). Unfortunatly, the board was made before I read the errata sheet in which it is mentionned that I2C2 on PB10/11 cannot be used in FastMode (Murphy Law

)

On this same board I have other peripherals on I2C3 that are working fine.

The problem is that I cannot managed to configure my I2C2 in standard mode so that I can be compliant with the errata and I can use those sensors.

If someone can help It would be so nice,

Regards,
Jeremy S.

Posted: **Mon Jun 03, 2019 3:16 pm**

Hi,

What is the problem exactly?

Giovanni

Posted: **Mon Jun 03, 2019 4:08 pm**

Hi Giovanni,

I forgot to post the I2C configuration. Here is the configuration:

Code: Select all

            STM32_TIMINGR_PRESC( 8U ) | STM32_TIMINGR_SCLDEL( 4U ) |
            STM32_TIMINGR_SDADEL( 2U ) | STM32_TIMINGR_SCLH( 15U ) |
            STM32_TIMINGR_SCLL( 19U ),
            0,
            0,

The problem is that with I2C2 configured on pin PB10/PB11 my chip is not responding to a ping command while on I2C3 with exact same configuration chip is working well.

Code: Select all

            // Set pad mode for I2C2
            palSetPadMode(
                GPIOB,
                10,
                PAL_MODE_ALTERNATE( 4 ) | PAL_STM32_OTYPE_OPENDRAIN );
            palSetPadMode(
                GPIOB,
                11,
                PAL_MODE_ALTERNATE( 4 ) | PAL_STM32_OTYPE_OPENDRAIN );

Posted: **Mon Jun 03, 2019 4:38 pm**

Hi again,

I found a configuration in ChibiOS testhal folder that fix my issue:

Code: Select all

  STM32_TIMINGR_PRESC(15U) |
  STM32_TIMINGR_SCLDEL(4U) | STM32_TIMINGR_SDADEL(2U) |
  STM32_TIMINGR_SCLH(15U)  | STM32_TIMINGR_SCLL(21U),
  0,
  0

Posted: **Mon Jun 03, 2019 7:28 pm**

Ah good

Do you have appropriate pullups externally?

Also note that in ChibiOS there is a little known I2C fallback implementation done in SW, when everything else fails you can try that.

Giovanni

Posted: **Fri Jun 07, 2019 8:20 am**

Thank you Giovanni for the help,

Yes my pullups are good so far.
I'll give a look at the fallback feature,

++

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