RE: PPI usage white paper?

Øyvind Karlsen — Fri, 15 Jul 2016 06:21:50 GMT

Well sure, just initialize the clock through the SoftDevice API. See the updated code above. To release the hfclk call sd_clock_hfclk_release(), which will happen immediately.

RE: PPI usage white paper?

Bret Foreman — Thu, 14 Jul 2016 20:05:06 GMT

Øyvind,

Won't the direct use of TIMER1 in the way you show above cause a conflict with the SoftDevice? I'm under the impression that timer control needs to go through the SD APIs when the SD is running.

Bret

RE: PPI usage white paper?

Øyvind Karlsen — Thu, 14 Jul 2016 06:28:03 GMT

Hi,

I wrote some code for this earlier, for 4 MHz output on pin 18 set NRF_TIMER1->CC[0] = 8;.

int main(void)
{
    // Set up GPIO as output
    nrf_gpio_range_cfg_output(17, 18);
    nrf_gpio_pin_clear(17); // Light LED 1 to indicate that the code is running
    
    // Start high frequency clock without SoftDevice
    NRF_CLOCK->TASKS_HFCLKSTART = 1;
    while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0)
    {
        // Wait for clock to start
    }

    // Start high frequency clock with SoftDevice
    uint32_t running;
    sd_clock_hfclk_request();
    sd_clock_hfclk_is_running(&running);
    while(!running)
    {
        sd_clock_hfclk_is_running(&running);
        //Wait for clock to start
    }

    NRF_CLOCK->EVENTS_HFCLKSTARTED = 0;
    
    // Configure GPIOTE to toggle pin 18 
    NRF_GPIOTE->CONFIG[0] = GPIOTE_CONFIG_MODE_Task << GPIOTE_CONFIG_MODE_Pos |
                            GPIOTE_CONFIG_POLARITY_Toggle << GPIOTE_CONFIG_POLARITY_Pos |
                            18 << GPIOTE_CONFIG_PSEL_Pos | 
                            GPIOTE_CONFIG_OUTINIT_Low << GPIOTE_CONFIG_OUTINIT_Pos;
                            
    // Set up timer
    NRF_TIMER1->PRESCALER = 0;
    NRF_TIMER1->CC[0] = 2; // Adjust the output frequency by adjusting the CC.
    NRF_TIMER1->SHORTS = TIMER_SHORTS_COMPARE0_CLEAR_Enabled << TIMER_SHORTS_COMPARE0_CLEAR_Pos;
    NRF_TIMER1->TASKS_START = 1;
        
    // Set up PPI to connect the timer compare event with the GPIOTE toggle task
    NRF_PPI->CH[0].EEP = (uint32_t) &NRF_TIMER1->EVENTS_COMPARE[0];
    NRF_PPI->CH[0].TEP = (uint32_t) &NRF_GPIOTE->TASKS_OUT[0];
    
    NRF_PPI->CHENSET = PPI_CHENSET_CH0_Enabled << PPI_CHENSET_CH0_Pos;
    
    while (true)
    {
       
    }
}

You can also see this post.

Best regards,

Øyvind