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Timer Issue With HX711 - Stopped By Vector Catch Error

Details: SDK v15.2.0 using HX711 sample code copy-pasted over twi_master_using_nrf_twi_mngr example. Windows 8.1, uploading to nRF52 DK.

I am having a hard time understanding this section of code. I read the timer section in the product specs v1.4, but I am clearly still not understanding it fully.

  • When I run it in the debugger, it loops through the do-while loop in the section of code below a lot and never increments any timer1 or timer2 register values. I added the NRF_LOG_INFO((int) NRF_TIMER2->CC[1]); line to try and readout the value but it just sends LOG: "blank"
  • When I build and run it on the board, it tells me "stopped by vector catch"

for (uint32_t i=0; i < ADC_RES; i++)
    {
        do
        {
            /* NRF_TIMER->CC[1] contains number of clock cycles.*/
            NRF_TIMER2->TASKS_CAPTURE[1] = 1;
            if (NRF_TIMER2->CC[1] >= ADC_RES) goto EXIT; // Readout not in sync with PD_CLK. Abort and notify error.
            else { 
              NRF_LOG_INFO((int) NRF_TIMER2->CC[1]); 
              NRF_LOG_FLUSH();
            }
        }
        while(NRF_TIMER1->EVENTS_COMPARE[0] == 0);
        NRF_TIMER1->EVENTS_COMPARE[0] = 0;
        m_sample.value |= (nrf_gpio_pin_read(DOUT) << (23 - i));
        m_sample.count++;
    }

When I read the code above, it tells me this:

  • loop through until i equals the number of ADC bits desired
  • capture timer2 value to CC[1] register
  • if: CC[1] (set to timer2 value) is equal or greater than ADC bits then exit (but timer2 was never started, why??)
  • else: logger
  • continue to do this until timer1 events_compare[0] is not zero (but CC[0] was initialised to 1, and events_compare would only go high if timer1 was equal to the value in CC[0] so unless timer1 overflows, it's unlikely it will catch??)
  • reset events_compare[0]

This code was written by Vidar so I'm sure it works fine. I feel like I'm doing something wrong

My main function looks like this:

int main(void) {
    /* Initialise logging */
    uint32_t err_code = NRF_LOG_INIT(NULL);
    APP_ERROR_CHECK(err_code);
    NRF_LOG_DEFAULT_BACKENDS_INIT();

    /* Initialise hx711 */
    hx711_mode_t mikes_mode;
    hx711_init(mikes_mode, m_evt_handler);
    hx711_start(false);
    NRF_LOG_FLUSH(); // push out message

    while(true) {
        NRF_LOG_INFO("print me");
        nrf_drv_gpiote_in_event_disable(DOUT); // maybe needed
        hx711_sample(); // Getting caught here
        nrf_delay_ms(1000);
        NRF_LOG_FLUSH();
    }
}

Parents
  • hello. I've been powering the hx711 with the VDD pin, which I saw supplies about 3V on my board. I have then been using the hx711 to supply the excitation voltage to the load cell. I realised that this reduces the sensitivity greatly. My question is if I was to externally excite the load cell, with, say 5V, would it affect my readings with the nrf52840, given that i saw the absolute maximum Vi/o rating is 3.9V?

Reply
  • hello. I've been powering the hx711 with the VDD pin, which I saw supplies about 3V on my board. I have then been using the hx711 to supply the excitation voltage to the load cell. I realised that this reduces the sensitivity greatly. My question is if I was to externally excite the load cell, with, say 5V, would it affect my readings with the nrf52840, given that i saw the absolute maximum Vi/o rating is 3.9V?

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