how to wake up from IDLE mode using ppi?

RE: how to wake up from IDLE mode using ppi?

Einar Thorsrud — Tue, 06 Sep 2016 11:41:44 GMT

For debugging printf should be OK (in a loop or not), but you should not use it for production, as you will have higher current consumption etc. Also, in general debugging with printf's can be a bad idea, as it will be easy to misunderstand the order of events. Have you for example verified that there is no error check that causes a reset, which would make it seem like the looping is constant, when what might really be happening is that main() is constantly started again after each reset? How have you verified that the CPU does not go to sleep?

RE: how to wake up from IDLE mode using ppi?

Haruki Kawakami — Mon, 05 Sep 2016 06:32:02 GMT

could you answer above question?

RE: how to wake up from IDLE mode using ppi?

Haruki Kawakami — Fri, 02 Sep 2016 02:29:30 GMT

hi I tried commenting out printf in while loop, then CPU sleep again and printf in timer_event_handler runs every 2ms and BSP_LED_0_MASK(LED1) blinks. printf in while loop is bad coding?

RE: how to wake up from IDLE mode using ppi?

Haruki Kawakami — Fri, 02 Sep 2016 01:47:47 GMT

Hi, of course I defined them like below.

const nrf_drv_timer_t timer1 = NRF_DRV_TIMER_INSTANCE(1);

nrf_ppi_channel_t ppi_channel1;

void uart_error_handle(app_uart_evt_t * p_event)
{
    if (p_event->evt_type == APP_UART_COMMUNICATION_ERROR)
    {
        APP_ERROR_HANDLER(p_event->data.error_communication);
    }
    else if (p_event->evt_type == APP_UART_FIFO_ERROR)
    {
          APP_ERROR_HANDLER(p_event->data.error_code);
    }
}

RE: how to wake up from IDLE mode using ppi?

Einar Thorsrud — Thu, 01 Sep 2016 12:18:16 GMT

Can you post the rest of your code as well? For example ppi_channel1 is not defined anywhere, and neither is timer1.

RE: how to wake up from IDLE mode using ppi?

Haruki Kawakami — Thu, 01 Sep 2016 11:20:02 GMT

Hi I paste my codes.

void timer_event_handler(nrf_timer_event_t event_type, void * p_context){
    printf("kumi %d\n\r", nrf_gpio_pin_read(LED_1));
}

static void ppi_init(void)
{
    uint32_t err_code = NRF_SUCCESS;

    err_code = nrf_drv_ppi_init();
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_ppi_channel_alloc(&ppi_channel1);
    APP_ERROR_CHECK(err_code);
    err_code = nrf_drv_ppi_channel_assign(ppi_channel1,
                                          nrf_drv_timer_event_address_get(&timer1, NRF_TIMER_EVENT_COMPARE0),
                                          NRF_GPIOTE->EVENTS_PORT);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_ppi_channel_enable(ppi_channel1);
    APP_ERROR_CHECK(err_code);
}

static void timer1_init(void)
{
    ret_code_t err_code = nrf_drv_timer_init(&timer1, NULL, timer_event_handler);
    APP_ERROR_CHECK(err_code);

    nrf_drv_timer_extended_compare(&timer1, NRF_TIMER_CC_CHANNEL0, 0x7FFFUL, NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK, false);
}

int main(void)
{
    uint32_t err_code;

    timer1_init(); // Timer to generate events on even number of seconds.

    nrf_drv_timer_compare_int_enable(&timer1, NRF_TIMER_CC_CHANNEL0);
    const app_uart_comm_params_t comm_params =
     {
         RX_PIN_NUMBER,
         TX_PIN_NUMBER,
         RTS_PIN_NUMBER,
         CTS_PIN_NUMBER,
         APP_UART_FLOW_CONTROL_ENABLED,
         false,
         UART_BAUDRATE_BAUDRATE_Baud115200
     };

    APP_UART_FIFO_INIT(&comm_params,
                    UART_RX_BUF_SIZE,
                    UART_TX_BUF_SIZE,
                    uart_error_handle,
                    APP_IRQ_PRIORITY_LOW,
                    err_code);

    APP_ERROR_CHECK(err_code);

    nrf_drv_timer_enable(&timer1);

    while (true)
    {
        __WFI();
        printf("Current count\n\r");
        if(LED_IS_ON(BSP_LED_0_MASK)){
            LEDS_OFF(BSP_LED_0_MASK);
       } else {
           LEDS_ON(BSP_LED_0_MASK);
       }
    }
}

RE: how to wake up from IDLE mode using ppi?

Einar Thorsrud — Thu, 01 Sep 2016 11:11:19 GMT

When you use the driver you should not have to clear the interrupt explicitly (as you do with nrf_timer_event_clear(), as it is done by the driver. You can see this in nrf_drv_timer.c, where the irq_handler() calls nrf_timer_event_clear() just before it calls the event handler you registered with the call to nrf_drv_timer_init().

I don't understand why your CPU does not go back to sleep, though. Can you double-check?

RE: how to wake up from IDLE mode using ppi?

Haruki Kawakami — Thu, 01 Sep 2016 10:47:28 GMT

I made it to wake CPU using nrf_drv_timer_compare_int_enable(), but I can't make CPU sleep again.

It seems that compare event is always true once happened. then I've used nrf_timer_event_clear to make compare event false, but cannot resolve this problem.

how can i make CPU sleep again?

 while (true)
{
    __WFI();
    printf("Current count\n\r");
    nrf_timer_event_clear(timer1.p_reg, nrf_timer_compare_event_get(NRF_TIMER_CC_CHANNEL0));
}

RE: how to wake up from IDLE mode using ppi?

Einar Thorsrud — Thu, 01 Sep 2016 09:07:27 GMT

Yes, if you enable the interrupt for the relevant compare event in the INTENSET register (directly, or by using nrf_drv_timer_compare_int_enable() as you already use the timer driver).

RE: how to wake up from IDLE mode using ppi?

Haruki Kawakami — Thu, 01 Sep 2016 09:01:24 GMT

do the compare event wake the CPU?

RE: how to wake up from IDLE mode using ppi?

Einar Thorsrud — Thu, 01 Sep 2016 08:58:32 GMT

PPI is used to connect peripherals, for example TIMER0 and TIMER1 in your case. If you want to wake the CPU on a compare event (for example on TIMER1 which you use to stop TIMER0) you should enable the compare interrupt. Using the timer driver you can do this with nrf_drv_timer_compare_int_enable().