Clock inaccuracy of nRF52832 custom board

[barky]

When using uart example on my curstom board, from /examples/peripheral/uart ,at baudrate 9600, bits are read with a little offset - so that starting from 4th bit, it is mistaken with the fallowing bit.

When measuring with logic analyzer, lenght of each bit is 92us, but it should be 104us at this baudrate.

The function nrf_delay_ms(100) gives a delay of 88.67ms.

I have solderd both 32MHz and 32.768KHz crystals on board, but for this example i am pretty sure i am using internal clock.

Any suggestions? Thanks

[Kenneth]

Hi, have you started the external crystal oscillator by calling NRF_CLOCK->TASKS_HFCLKSTART = 1;?

http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/clock.html?cp=2_1_0_18_2#topic 

[barky]

As i mentioned earlier, the clock became accurate after placing crystal in correct position (90 degrees).

For example, each bit lenght of uart message is now 104uS as supposed to, but program halts on:

//while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0) {}

loop. So crystal kinda works.

As i read in other threads, maybe there is wrong capacitors placed on DEC pins...

Any suggestions?

[Kenneth]

Is the softdevice enabled? 

[barky]

Yea it is...

I used blinky example with with s132 softdevice, added lines:

NRF_CLOCK->EVENTS_HFCLKSTARTED = 0;

NRF_CLOCK->TASKS_HFCLKSTART = 1;

nrf_delay_ms(300);

// Wait for the external oscillator to start up

while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0) {}

And its still stuck...

I have the LF_clock also on the board, maybe configuration with it are messing with software.

[Kenneth]

If the softdevice is enabled, then you need to use:

sd_clock_hfclk_request();
while(!sd_clock_hfclk_is_running());

...

sd_clock_hfclk_release();

 

[barky]

int main(void)
{
    /* Configure leds. */
    nrf_gpio_cfg_output(LED_3);

    //Initialize HFCLK 
	uint32_t p_is_running;
    
    (void)sd_clock_hfclk_request();
    do { 
        sd_clock_hfclk_is_running(&p_is_running); 
    }while(p_is_running==0);

    while (true)
    {
        nrf_delay_ms(500);
        nrf_gpio_pin_set(LED_3);
        nrf_delay_ms(500);
        nrf_gpio_pin_clear(LED_3);
    }
}

I tried this code and it stuck, when using softdevice.

From infocenter: "parameter p_is_running results in 1 if the external crystal oscillator is running, 0 if not."

Moreover, return value of "sd_clock_hfclk_is_running" is 0 or "NRF_SUCCESS" if successful.

I found issue, quite relevant: Case ID: 117750 ,where DC-DC power caps were cold soldered, maybe my case is similar, even though i checked all connections and values of passive components (i am useing internal LDO configuration).

[Kenneth]

Hi, to use the softdevice api you will first need to enable the softdevice.