TWI in Low Power...

[Brian]

Hey guys,

Trying to use TWI in the lowest power way possible, non-blocking. Is this the right way to do it? When I run this, I get the callback event handler to execute once, and once only -- seemingly stuck in WFE() or sd_app_evt_wait() , not waking up with the callback. Any ideas as to why?

  nrf_drv_twi_init(&p_twi_instance, &p_twi_config, twi_event_handler); 
  nrf_drv_twi_enable(&p_twi_instance); // Enable the TWI instance   

while(1) {
 
    nrf_drv_twi_rx(&p_twi_instance, 0x55, dummy_data, 7, false);          

    //power_manage(); //sd_app_evt_wait(); //if using SD                                                                                                                                        
    __WFE();   
}
    
static void twi_event_handler(nrf_drv_twi_evt_t *p_evt){   
    if(p_evt->type == NRF_DRV_TWI_RX_DONE)
    {

      SEGGER_RTT_printf(0, "\n\nDATA: ", dummy_data);
      for(i=0;i<7;i++) SEGGER_RTT_printf(0, "%02x ", dummy_data[i]);

    } 
}

[Brian]

Yeah... I just put a flag around the call to nrf_drv_twi_rx and that worked.

if(RX_ready) nrf_drv_twi_rx..., then RX_ready=FALSE

Then set RX evt handler, I set RX_ready to TRUE.

Curious why we exit WFE so quickly without valid TWI data though. I don't know of anything else going on that would interrupt things. Has this TWI driver been optimized for power at all?

Thanks!

[MartinBL]

Maybe you are getting the NACK event I have mentioned in the comment above. You will get the event right after your nRF5x has transmitted the address and not gotten any response. You won't get any valid data either.