2 Timers as counter with external input capture pin

[Amigo]

Hi. I have to make mesuring impulses quantity of two external low freq signals without interrupts.

I tried to use GPIOTE EVENTS_IN[0] and 1 with PPI ch 0 and 1 to timer 2 and 3 TASKS_COUNT generate. it works, but when the event on pins polarity change occure simultaneously one of the timers counts twice. 

How to make it write to be timers counted independently of each other?

[Håkon Alseth]

Hi,

 

Could you share a piece of the code where you tie everything together, so I can look at the logic?

Are the signals occurring within a very short period of time? If yes, then it might be that you are running into this errata: http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.Rev1.errata/anomaly_832_155.html?cp=2_1_1_1_1_44

 

Best regards,

Håkon

 

[Amigo]

Delay between signals 1 - 1.5 ms/

Code (next i remake without ppi)

void in_pin_handler(nrf_drv_gpiote_pin_t pin, nrf_gpiote_polarity_t action)

void in_pin_handler(nrf_drv_gpiote_pin_t pin, nrf_gpiote_polarity_t action)

		if( pin == 4 )
		{	
			counter1++;
			SEGGER_RTT_WriteString(0,"CNT1\r\n");
		}
		else if( pin == 5 )
		{			
			counter2++;
			SEGGER_RTT_WriteString(0,"CNT2\r\n");
		}
}

static void buttons_leds_init(bool * p_erase_bonds)
{
	nrf_gpio_cfg_output(17);
	nrf_gpio_cfg_output(18);
	nrf_gpio_cfg_output(19);
	nrf_gpio_cfg_output(20);
	nrf_gpio_pin_set(17);
	nrf_gpio_pin_set(18);
	nrf_gpio_pin_set(19);
	nrf_gpio_pin_set(20);

	err_code = nrf_drv_gpiote_init();
    APP_ERROR_CHECK(err_code);
	
    nrf_drv_gpiote_in_config_t in_config = GPIOTE_CONFIG_IN_SENSE_HITOLO(true);
    in_config.pull = NRF_GPIO_PIN_PULLUP;
    nrf_drv_gpiote_in_init(4, &in_config, in_pin_handler);
    nrf_drv_gpiote_in_event_enable(4, true);
    nrf_drv_gpiote_in_init(5, &in_config, in_pin_handler);
    nrf_drv_gpiote_in_event_enable(5, true);
    
    NVIC_SetPriority(2, GPIOTE_IRQn);
    NVIC_DisableIRQ(GPIOTE_IRQn);
}

cnt2 sets twice

[Håkon Alseth]

Your code does not use PPI. Do you still see double-events with this code? Have you scoped pin 5 to see if there are any glitches or pulses that might account for this double increment?

Is your counter values declared as volatile? This is important when variables are used in interrupt vectors.

 

Best regards,

Håkon

[Amigo]

With PPi or not, it has double event. There is no pulses (i use cap 0.1 uf on input pins). Variables are volatile but SEGGER_RTT_WriteString(0,"CNT2\r\n"); prints twice

[Håkon Alseth]

I assume your inputs should then alternate between CNT1 and CNT2, ie: the input signal phase is 0/180 degrees.

Could you try to omit RTT, and do something like this to see if this might be a RTT polling/buffering issue?

void in_pin_handler(nrf_drv_gpiote_pin_t pin, nrf_gpiote_polarity_t action)
{
        static nrf_drv_gpiote_pin_t last_pin;
		if( pin == 4 )
		{	
			counter1++;
			//SEGGER_RTT_WriteString(0,"CNT1\r\n");
		}
		else if( pin == 5 )
		{			
			counter2++;
			//SEGGER_RTT_WriteString(0,"CNT2\r\n");
		}
		if (pin == last_pin)
		{
		  // Same evt happen twice in a row.
		  static uint32_t double_count;
		  double_count++;
		}
		last_pin = pin;
}

 

Best regards,

Håkon

[Amigo]

All the same. RTT does not affect

[Håkon Alseth]

Could you try to enable this errata workaround, just to see if the two signals are triggered, at some point, very close together?

http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.Rev2.errata/dita/errata/nRF52832/Rev2/latest/anomaly_832_155.html?cp=2_1_1_0_1_41

 

Best regards,

Håkon

[Amigo]

Yes, i tried, i use construction from errata with in GPIOTE initialising. if GPIOTE_CH_USED is pin number like 4 or 5, i made it write. But it has no effect.



[Håkon Alseth]

It is not the pin used, but the GPIOTE->IN[] instance used. If there are no other IN channels in use, then this is 0 and 1.