High-frequency GPIO

RE: High-frequency GPIO

Thiago — Wed, 11 Nov 2020 11:04:59 GMT

It works fine now. Thank you very much for your help.

RE: High-frequency GPIO

Dmitry — Wed, 11 Nov 2020 08:52:06 GMT

Hi,

you have set TIMER_INSTANCE->CC[0] = 1, so CPU spends all the time in TIMER2_IRQHandler, not leaving any time for low-priority processes.

RE: High-frequency GPIO

Thiago — Wed, 11 Nov 2020 08:19:36 GMT

Hello,

After following the suggestions above:

[quote userid="5418" url="~/f/nordic-q-a/68095/high-frequency-gpio/278899#278899"] I think sprintf() and SEGGER_RTT_WriteString() eat most of these 57 microseconds, try to comment them out. To achieve maximum frequency, use HAL module functions (nrf_timer.h) instead of nrf_drv_timer[/quote]

I got an improvement in the frequency of almost 18 times as seen in this image:

I used this code to initialize the clock and for the Interrupt service routine:

#define TIMER_INSTANCE NRF_TIMER2
 /*---------------------------------------------------------------------------*/
 void
 timer2_init(void)
 {
    TIMER_INSTANCE->PRESCALER = 0;

    TIMER_INSTANCE->TASKS_STOP = 1;	/* Stop timer */
    TIMER_INSTANCE->MODE = TIMER_MODE_MODE_Timer;  /* taken from Nordic dev zone */
    TIMER_INSTANCE->BITMODE = TIMER_BITMODE_BITMODE_16Bit;
    TIMER_INSTANCE->CC[0] = 1;
    TIMER_INSTANCE->TASKS_CLEAR = 1; /* Clear timer */
    TIMER_INSTANCE->INTENSET = TIMER_INTENSET_COMPARE0_Enabled << TIMER_INTENSET_COMPARE0_Pos;
    TIMER_INSTANCE->SHORTS = (TIMER_SHORTS_COMPARE0_CLEAR_Enabled << TIMER_SHORTS_COMPARE0_CLEAR_Pos);
    
    NVIC_ClearPendingIRQ(TIMER2_IRQn);
    NVIC_SetPriority(TIMER2_IRQn, 6);
    NVIC_EnableIRQ(TIMER2_IRQn);

    

    TIMER_INSTANCE->TASKS_START = 1;
 }


 void
 TIMER2_IRQHandler(void)
 {
     if (TIMER_INSTANCE->EVENTS_COMPARE[0] != 0)
    {
    	TIMER_INSTANCE->EVENTS_COMPARE[0] = 0;

        if(currentSample < 10){
            GPIO0_OUT_R &= ~(0xFF<<18);   
            GPIO0_OUT_R |= ((SineWave[currentSample])<<18);   
            //sprintf(GPIO_Out_current_Value, "GPIO0_OUT register current value: %d\n", (GPIO0_OUT_R>>18)&0xFF);
            //SEGGER_RTT_WriteString(0, GPIO_Out_current_Value);
            currentSample++;
        }
        else{
            currentSample = 0;
        }

    	TIMER_INSTANCE->SHORTS = TIMER_SHORTS_COMPARE0_CLEAR_Msk;
    }
 }

The frequency improvement is great, but the module is not advertising anymore.

If I don't make a call for the timer2_init() function in the main(), it advertises, but not otherwise.

I wrote the code based on the ble_app_uart example. I changed nothing in the BLE configuration.

The main function is looking like this now:

/**@brief Application main function.
 */
int main(void)
 {
    bool erase_bonds;   

    //NRF_CLOCK->TASKS_HFCLKSTART = 1;

    // Initialize.
    uart_init();
    log_init();
    timers_init();    
    leds_init(&erase_bonds);
    gpio_init();
    power_management_init();
    ble_stack_init();
    conn_evt_ext_enable();
    data_len_set(DATA_LENGTH_MAX);
    gap_params_init();
    gatt_init();
    services_init();
    timer2_init();
    //digital_signal_event_init();

    //saadc_init();
    //saadc_sampling_event_init();
    

    advertising_init();
    conn_params_init();

    // Start execution.
    printf("\r\nUART started.\r\n");
    NRF_LOG_INFO("Debug logging for UART over RTT started.");
    SEGGER_RTT_WriteString(0, "Debug logging for UART over RTT started.\n");


    advertising_start();

    //saadc_sampling_event_enable();



    // Enter main loop.
    for (;;)
    {
        idle_state_handle();
              
    }
}

Would anyone have a clue why the advertising stops or what could I do to find out how to solve it?

RE: High-frequency GPIO

Thiago — Mon, 09 Nov 2020 08:28:58 GMT

Thank you.

I'll check the reference you provided.

[quote userid="5418" url="~/f/nordic-q-a/68095/high-frequency-gpio/278927#278927"]If you're using BLE stack, you'll need to configure other timer instance because TIMER0 is occupied by SoftDevice.[/quote]

Oh! I noticed that before but I didn't know why it happened. Thank you!

RE: High-frequency GPIO

Dmitry — Mon, 09 Nov 2020 07:54:22 GMT

You can look at source code of Contiki-NG timer module. If you're using BLE stack, you'll need to configure other timer instance because TIMER0 is occupied by SoftDevice.

RE: High-frequency GPIO

Thiago — Mon, 09 Nov 2020 05:27:11 GMT

Hello.

Thank you for your suggestions.

Just by removing the debugging functions I already noticed a 5x improvement in the frequency. I wrote the code based on the examples found in the nRF5_SDK_16. There, they use the functions in the nrf_drv_timer for timer initialization. Would you know where I could find examples of timer initialization using the functions in the nrf_timer.h?

RE: High-frequency GPIO

Dmitry — Sun, 08 Nov 2020 20:37:49 GMT

Hi,

as I understood from oscilloscope screenshot, you have a 57-us interval between GPIO switching. I think sprintf() and SEGGER_RTT_WriteString() eat most of these 57 microseconds, try to comment them out. To achieve maximum frequency, use HAL module functions (nrf_timer.h) instead of nrf_drv_timer, and write an irq handler (as short as possible) by yourself.