Timer Issue With HX711 - Stopped By Vector Catch Error

[mbards]

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();
    }
}

[Eugene0469]

which pins of your nrf dev kit did you use, cause I'm using Arduino pin 5 and 4 and I only seem to be reading 0 values. any help would be greatly appreciated.

[Vidar Berg]

It shouldn't be a problem to use pin 5 and 4 as long as they are not used for anything else in your code. Have you tried compiling with code optimization enabled? It may be necessary to read out the DOUT pin fast enough. Are you powering the hx711 through another GPIO?

[Eugene0469]

I am using optimization level -o3and I am powering the hx711 through the 5V pin provided by the nrf52840

[Vidar Berg]

You will exceed the maximum rating for I/O pin voltage on the chip if you supply 5v, which may damage the chip. The digital logic should be equal to VDD. 

[Eugene0469]

Thanks. I switched from the 5V pin to VDD pin and now I am getting the values

[Eugene0469]

I'd like to ask, when I went through the hx711 code written for Arduino, there was the issue of calibrating the hx711. Maybe it has already been done in the program. If so, I kindly ask for your direction to that section of the program.

[Vidar Berg]

Calibration is not included in this code unfortunately. You need to implement it in your app. E.g., implement BLE commands to set calibration points, do linear regression, and store the curve to flash. 

[Eugene0469]

Ok. Thank you very much for all the help you've offered me.