TWI restart condition after a rx operation (IQS263)

RE: TWI restart condition after a rx operation (IQS263)

Aurele — Wed, 10 Jun 2020 16:30:49 GMT

Hello Kenneth,

I succeeded to make what i want by modifying the current driver in the SDK16 and also with the deprecated driver but i'm facing other issues with the IQS263 that is internaly reseting because of stalling on I2C line. For instance, now, i'm only doing a single read on each event (and not 3 as i wanted at the beginnig) ...

Regards

RE: TWI restart condition after a rx operation (IQS263)

Kenneth — Tue, 09 Jun 2020 12:01:59 GMT

Hmm.. For sure the deprecated software implementation should be able to do this. Have you tried that one also?

Best regards,
Kenneth

RE: TWI restart condition after a rx operation (IQS263)

Aurele — Fri, 05 Jun 2020 09:30:31 GMT

Thank's for these informations. I tried to modify the legacy driver : nrfx_twi.c file in that way :

extern bool rx_no_stop;
static bool twi_receive_byte(NRF_TWI_Type         * p_twi,
                             twi_control_block_t  * p_cb)
{
    if (p_cb->bytes_transferred < p_cb->curr_length)
    {
        p_cb->p_curr_buf[p_cb->bytes_transferred] = nrf_twi_rxd_get(p_twi);
        ++(p_cb->bytes_transferred);

        if ((p_cb->bytes_transferred == p_cb->curr_length - 1) && (!TWI_FLAG_SUSPEND(p_cb->flags)))
        {
            nrf_twi_shorts_set(p_twi, NRF_TWI_SHORT_BB_STOP_MASK);
        }
        else if (p_cb->bytes_transferred == p_cb->curr_length && (!TWI_FLAG_SUSPEND(p_cb->flags)))
        {
            if (rx_no_stop)
            {
                nrf_twi_task_trigger(p_twi, NRF_TWI_TASK_SUSPEND);
                p_cb->prev_suspend = TWI_SUSPEND_RX;
            }
            return true;
        }
        else if (p_cb->bytes_transferred == p_cb->curr_length && TWI_FLAG_SUSPEND(p_cb->flags))
        {
            p_cb->prev_suspend = TWI_SUSPEND_RX;
            return false;
        }
        nrf_twi_task_trigger(p_twi, NRF_TWI_TASK_RESUME);
    }
    return true;
}

but without success.

I tried also to use the deprecated driver but unfortunatly it is still not working. Im still having a stop sent at the end of my RX ...

RE: TWI restart condition after a rx operation (IQS263)

Kenneth — Thu, 04 Jun 2020 11:05:23 GMT

The TWI hardware may operate in two modes; legacy TWI mode (where each byte is loaded from the CPU) and TWIM mode (where each transfer is started using EasyDMA). The mode is controlled by TWI0_USE_EASY_DMA. When using legacy mode you are including the api from nrf_twi.c and not nrfx_twim.c. I would think that using legacy is the preferred here to have better control over this, so make sure that is the case when you are modifying.

If that doesn't work, I can also find that in \components\drivers_nrf\twi_master\deprecated there are both older hardware and software implementation that may give better low level control of this. Though they are using hardcoded PPI channels, so you may need to modify that to use one that is available in your application.

Best regards,
Kenneth

RE: TWI restart condition after a rx operation (IQS263)

Aurele — Thu, 04 Jun 2020 10:45:20 GMT

Unfortunaly i tried to modify the sdk library (nrfx_twi driver), it was almost working but the bytes i'm receiving don't look good.

So i'm still looking for a solution.

RE: TWI restart condition after a rx operation (IQS263)

Kenneth — Wed, 03 Jun 2020 18:58:11 GMT

Looks like you are right. Then I suppose it may be possible by calling nrfx_twi_xfer()/nrfx_twim_xfer() directly, instead of using the nrf_drv_twi_rx() wrapper.

Best regards,
Kenneth

RE: TWI restart condition after a rx operation (IQS263)

Aurele — Tue, 02 Jun 2020 14:23:29 GMT

Hi,

Thank you very much for the reply. The NO_STOP flag seems to be available only for TX mode, not RX mode !

RE: TWI restart condition after a rx operation (IQS263)

Kenneth — Tue, 02 Jun 2020 12:29:35 GMT

I believe using the NO_STOP flag should solve this, check out:
https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v15.3.0/hardware_driver_twi.html#hardware_driver_twi_advanced