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TWI Clearing Bus with NRFX_TWI driver

Allen Jameson

Hello,

We are using the NRFX_TWI driver which we understand is a new and improved version of the legacy NRF_DRV_TWI driver.  However we are getting a number of apparent stuck-bus errors if our app breaks in the wrong place, and have to completely remove power from the system to get everything un-stuck (simply restarting the code does not help).

It appears this is a common problem and the solution given in https://devzone.nordicsemi.com/f/nordic-q-a/21508/twi-stuck-bus-recovery seems to be simple enough.  However I cannot find an analog for the NRFX_TWI driver, as this is not a valid parameter in the config_t struct:

static const nrfx_twi_config_t twi_config = {
.scl = TWI_SCL,
.sda = TWI_SDA,
.frequency = NRF_TWI_FREQ_400K,
//.clear_bus_init=true, //does not work
.interrupt_priority = TWI_DEFAULT_CONFIG_IRQ_PRIORITY};

Could you advise as to how to clear the bus?

Thanks!

--Allen

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  • 0

    Hi Allen,

    As I understand it, NRFX drivers are not the replacement for nrf_drv.

    We want to use the same hal layer over different solutions we have so that the underlying hal layer is not implemented in different ways in different solutions.

    So the nrf_drv_twi API is still the same, the change is that now it uses nrfx_twi below it.

    And in SDK15 you still have the same API for nrf_twi and you still have the clear_bus_init option.

    Now assuming that you know all the above, if you say that the clear_bus_init option is not working. then I am little confused as this option just uses the gpio set clear option and it has not changed at all.

        if(p_config->clear_bus_init)
    {
        /* Send clocks (max 9) until slave device back from stuck mode */
        twi_clear_bus(p_config);
    }

  • 0 in reply to Susheel Nuguru

    Aryan,

    As with Andy's reply, I also do understand it that the nrfx drivers are the replacement.  That certainly seems to be how they are described in the documentation.  The "nrf_drv" calls in SDK15 are the wrapper, but the underlying layer is now nrfx.  

    I think you are right that if we continue to use the nrf_drv wrappers (although the recommendation is to stop using them) we can use the p_config->clear_bus_init property to clear the bus on init.  But it appears that the nrf_drv wrappers will be deprecated at a certain point.

    @Andy what I did for my project was just copy the twi_clear_bus function into the nrfx_twi.c file, calling it nrfx_twi_clear_bus.  Then when I am going to call nrfx_twi_init() I first call nrfx_twi_clear_bus().  I could have instead put that call into the nrfx_twi_init function, but that would have required modifying the config structure.  

    I suspect / hope this will be included in nrfx_drv_twi in a future release.

    Best,

    --Allen

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  • 0 in reply to Susheel Nuguru

    Aryan,

    As with Andy's reply, I also do understand it that the nrfx drivers are the replacement.  That certainly seems to be how they are described in the documentation.  The "nrf_drv" calls in SDK15 are the wrapper, but the underlying layer is now nrfx.  

    I think you are right that if we continue to use the nrf_drv wrappers (although the recommendation is to stop using them) we can use the p_config->clear_bus_init property to clear the bus on init.  But it appears that the nrf_drv wrappers will be deprecated at a certain point.

    @Andy what I did for my project was just copy the twi_clear_bus function into the nrfx_twi.c file, calling it nrfx_twi_clear_bus.  Then when I am going to call nrfx_twi_init() I first call nrfx_twi_clear_bus().  I could have instead put that call into the nrfx_twi_init function, but that would have required modifying the config structure.  

    I suspect / hope this will be included in nrfx_drv_twi in a future release.

    Best,

    --Allen

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