Questions about FreeRTOS and RTC on nrf52832

[Lurn_Z]

Hi all,

I am having an issue with FreeRTOS on the NRF52832 (SDK 17.1.0).

I need precise time so I use the io to measure the time. the code like this:

    nrf_gpio_cfg_output(18);
    PRINTF("nrf_gpio_cfg_output 18.");
    while(1)
    {
        nrf_gpio_pin_write(18, 1);
        vTaskDelay(1);
        nrf_gpio_pin_write(18, 0);
        vTaskDelay(1);
        nrf_gpio_pin_write(18, 1);
        nrf_delay_us(500);
        nrf_gpio_pin_write(18, 0);
        nrf_delay_us(500);
        nrf_delay_ms(10);
        PRINTF("while loop.");
    }

#define configTICK_RATE_HZ        1024

But the oscilloscope waveform shows that the interval is abnormal.

The first pullup interval is 738 us, and the first pulldown interval is 910us, but the second pullup interval is exact time 500us.

That means delay time on rtos is not accurate, but nrf_delay is accurate.

Did I set something wrong about freertos?

The config file is here.

8508.FreeRTOSConfig.h

5432.sdk_config.h

Hope you can give me some suggestions.

Best regards

Lurn

[Lurn_Z]

Hi Vidar,

After communicating the requirements, my colleagues and I believe that the focus of the problem should be on how to synchronize the three devices. Of course, time accuracy is also important, but it should be placed after synchronization. 

In this link, it shows how to sync the clock, and I will learn how to implement it, but I also have a question, after sync the time, How can I confirm that the two TX devices are separate? Like TX A at an odd time, TX B at even time.

Best regards,

Lurn

[Vidar Berg]

Discussion around device synchronization will continue in this thread:  (Missing Forum Thread)  

[Lurn_Z]

Hi Vidar,

In this link 

Vidar Berg said:

Here is the link:

 Wireless timer synchronization among nRF5 devices  

I found some IRQ_handler called by softdevice. But I didn't use the softdevice, I only use the ESB and not BLE, And I searched for some information, the timeslot looks like it should be used in BLE(I think).

So how to handle it?

BR,

Lurn