Asynchronous mode of timers

[kada]

Hello.

I need to count impulses going to nrf51822 in low power mode. I use the following code to configure GPIOTE and PPI to toggle counter and it works well:

#define PPI_CHANNEL 0 #define PULSE_INPUT_NUM 2 #define TIMER NRF_TIMER1

void initPulseCaptureInput (void) { // Configure GPIO nrf_gpio_cfg_sense_input(PULSE_INPUT_NUM, NRF_GPIO_PIN_NOPULL, NRF_GPIO_PIN_SENSE_HIGH);

// Clear TIMER TIMER->TASKS_CLEAR = 1;

// Configure TIMER for counter mode TIMER->MODE = TIMER_MODE_MODE_Counter; TIMER->BITMODE = TIMER_BITMODE_BITMODE_32Bit;

// Start TIMER TIMER->TASKS_START = 1;

NRF_PPI->CH[PPI_CHANNEL].EEP = (uint32_t)(&NRF_GPIOTE->EVENTS_PORT); NRF_PPI->CH[PPI_CHANNEL].TEP = (uint32_t)(&TIMER->TASKS_COUNT); NRF_PPI->CHENSET = (0x1UL << PPI_CHANNEL); }

But I noticed that current consumption is 1mA in sleep mode. So I guess that this current is high frequency oscillator supply current which need for timer operation? Is there any way to achieve low current consumption pulse counting in nrf51822?

[Hung Bui]

@kada: I can't reproduce the high current consumption as you described. In my test it's about 4 uA when idle. I attached here the test code. It's tested on PCA10028. (please ignore RTC and lfclk code). SDK v8.0 Which chip version on your board ?

rtc - GPIOPORT_COUNTER.zip

[kada]

Thank you, Hung Bui. I'm using RFduino board programming it directly from Arduino IDE. Later I can check your code when installed Keil uvision. Also my chip version is QFAACA. But I didn't find anything related to increasing power consumption when running Timer in the PAN. I guess the Timer 0, 1, 2 is in the PCLK16M domain and when you start Timer even in counter mode the HFCLK source switched on.

[Hung Bui]

@kada: The counter only requires HFCLK when it is active when COUNT task is triggered, when IDLE it should not let the HFCLK running. I suspect that you may have something else that keep the clock running.

[kada]

Just tested your code and I still have >1 mA current consumption. When I comment gpiote_init(); and counter_init(); function calls the current reduced to 2.8 uA. What is the problem? Thanks.

[Hung Bui]

@kada: I think I know the issue. It was because you are using chip version 1. If you look at the nRF51822-PAN_v2.2.pdf you can find issue #39 "GPIOTE: 1V2 + HFCLK are requested always when the GPIOTE task is configured” this causes the current consumption of 1mA.

If you remove GPIOTE Task it should drop to 2.8 uA.

I suggest you to continue development with XLR3 chip (included in nRF51 DK PCA10028)