nRF52810_preliminary_software_tests/main.c

#include <string.h>
#include <stdio.h>

#include <zephyr/kernel.h>
#include <zephyr/device.h>
#include <zephyr/sys/printk.h>
#include <zephyr/drivers/gpio.h>

#include <nrf_gpio.h>
#include <nrf_timer.h>

/* The devicetree node identifier for the "led0" alias. */

#define TST_CLK_PIN 18 //this is led 0 pin on nrf52-dk
#define FREQ_MEASURE_PIN 18

static const struct gpio_dt_spec led = GPIO_DT_SPEC_GET(DT_ALIAS(led0), gpios);
static const struct gpio_dt_spec led1 = GPIO_DT_SPEC_GET(DT_ALIAS(led1), gpios);

int count = 0;

void configure_clock_pin(uint32_t pin_number){
    nrf_gpio_cfg(
        pin_number,
        NRF_GPIO_PIN_DIR_OUTPUT,
        NRF_GPIO_PIN_INPUT_CONNECT,
        NRF_GPIO_PIN_NOPULL,
        NRF_GPIO_PIN_S0S1,
        NRF_GPIO_PIN_NOSENSE);
		*(volatile uint32_t *)(NRF_GPIOTE_BASE + 0x600 + (4 * pin_number)) = 1;
}


void gpio_clock_8m(uint32_t pin_number) {
    
    NRF_TIMER0->PRESCALER = 0; // 16MHz
    NRF_TIMER0->SHORTS = TIMER_SHORTS_COMPARE0_CLEAR_Msk;
    NRF_TIMER0->CC[0] = 0x3; //~1KHz //1 for 16/2=8MHz for, 2 for 8/2=4MHz, 4 for 4/2=2MHz etc..
	NRF_TIMER0->BITMODE = (TIMER_BITMODE_BITMODE_16Bit << TIMER_BITMODE_BITMODE_Pos);	
	//using config [1] since [0]
    NRF_GPIOTE->CONFIG[1] = GPIOTE_CONFIG_MODE_Task | (pin_number << GPIOTE_CONFIG_PSEL_Pos) |
                            (GPIOTE_CONFIG_POLARITY_Toggle << GPIOTE_CONFIG_POLARITY_Pos);

    /*Connect TIMER event to GPIOTE out task*/
	NRF_PPI->CHEN |= 1 << 3;
    *(&(NRF_PPI->CH3_EEP)) = (uint32_t) &NRF_TIMER0->EVENTS_COMPARE[0];
    *(&(NRF_PPI->CH3_TEP)) = (uint32_t) &NRF_GPIOTE->TASKS_OUT[1];
    NRF_PPI->CHENSET |= 1 << 3;

    /*Starts clock signal*/
    NRF_TIMER0->TASKS_START = 1;
}

static void timer_init() //gate timer
{
	NRF_TIMER1->TASKS_STOP = 1; //trigger stop
	NRF_TIMER1->MODE = TIMER_MODE_MODE_Timer; //mode timer
	NRF_TIMER1->PRESCALER = 4;	// Fhck / 2^8 -1MHz
	//total gate time of timer 10000 - 100mS
	NRF_TIMER1->CC[0] = 50000;	//end gate count
	NRF_TIMER1->CC[1] = 1;	//start gate count. don't start at 0 to no start on clear.
	
	NRF_TIMER1->BITMODE = (TIMER_BITMODE_BITMODE_32Bit << TIMER_BITMODE_BITMODE_Pos);	
	
	NRF_TIMER1->TASKS_CLEAR = 1; //trigger zero timer
	NRF_TIMER1->INTENSET = (TIMER_INTENSET_COMPARE0_Enabled << TIMER_INTENSET_COMPARE0_Pos); //interrupt on end gate count
	
	NRF_TIMER1->EVENTS_COMPARE[0] = 0; //rest event flag for gate end
	NRF_TIMER1->EVENTS_COMPARE[1] = 0; //rest event flag for gate start
}

static void counter_init() //actual counter
{
	NRF_TIMER2->TASKS_STOP = 1;	//trigger stop
	NRF_TIMER2->MODE = TIMER_MODE_MODE_Counter; //counter
	NRF_TIMER2->BITMODE = (TIMER_BITMODE_BITMODE_24Bit << TIMER_BITMODE_BITMODE_Pos);
	NRF_TIMER2->TASKS_CLEAR = 1; //trigger zero counter
	NRF_TIMER2->EVENTS_COMPARE[0] = 0; //reset event for compare
}

//counter input pin setting
static void gpiote_init(uint32_t pin)
{
	NRF_GPIOTE->CONFIG[0] 	= 	0x01 << 0; 								// MODE: Event
	NRF_GPIOTE->CONFIG[0] 	|= 	pin << 8;								// Pin number
	NRF_GPIOTE->CONFIG[0] 	|= 	GPIOTE_CONFIG_POLARITY_LoToHi	<< 16;		// Event rising edge 	
}

//hardware trigger: stop of counter on event of end timer1 gate
static void ppi_timer_stop_counter_init()
{
	NRF_PPI->CHEN |= 1 << 2; //channel
	*(&(NRF_PPI->CH2_EEP)) = (uint32_t)&NRF_TIMER1->EVENTS_COMPARE[0]; //attach end gate event
	*(&(NRF_PPI->CH2_TEP)) = (uint32_t)&NRF_TIMER2->TASKS_STOP; //to counter stop trigger
	NRF_PPI->CHENSET |= 1 << 2; //set channel
}

//hardware trigger: start of counter on event of begin timer1 (gate) event.gate
static void ppi_timer_start_counter_init()
{
	NRF_PPI->CHEN |= 1 << 4;// channel
	*(&(NRF_PPI->CH4_EEP)) = (uint32_t)&NRF_TIMER1->EVENTS_COMPARE[1]; //attach gate start event
	*(&(NRF_PPI->CH4_TEP)) = (uint32_t)&NRF_TIMER2->TASKS_START; //to counter start trigger
	NRF_PPI->CHENSET |= 1 << 4;
}


static void ppi_gpiote_counter_init()
//hardware attachment for the gpiote that was selected above
{
	NRF_PPI->CHEN |= 1 << 1;
	*(&(NRF_PPI->CH1_EEP)) = (uint32_t)&NRF_GPIOTE->EVENTS_IN[0]; //attach pin change
	*(&(NRF_PPI->CH1_TEP)) = (uint32_t)&NRF_TIMER2->TASKS_COUNT;//to one count
	NRF_PPI->CHENSET |= 1 << 1;
}

//gate end interrupt handler. Count is done at hardware and percice interrupt execution isnt critical
void TIMER1_IRQHandler(void) 
{
	if (NRF_TIMER1->EVENTS_COMPARE[0] != 0) //end gate event
	{
		gpio_pin_toggle_dt(&led);
		NRF_TIMER1->EVENTS_COMPARE[0] = 0; //reset end gate flag
		NRF_TIMER1->EVENTS_COMPARE[1] = 0; //reset start gate flag
		NRF_TIMER2->TASKS_CAPTURE[0] = 1; //trigger get counter value
		count = NRF_TIMER2->CC[0];
      	
		NRF_TIMER1->TASKS_CLEAR = 1; //reset timer
		NRF_TIMER2->TASKS_CLEAR = 1; //reset counter
						
		//NRF_TIMER1->TASKS_STOP = 1; //stop		
		NRF_TIMER1->TASKS_START = 1; //start next count gate		
    }
}


int main(void)
{
	printf("Helloworld! \n");
	nrf_gpio_cfg_input(14, NRF_GPIO_PIN_PULLUP);
	nrf_gpio_cfg_input(13, NRF_GPIO_PIN_PULLUP);


	int ret;
	if (!gpio_is_ready_dt(&led)) {
		return 0;
	}
	ret = gpio_pin_configure_dt(&led, GPIO_OUTPUT_ACTIVE);

	ret = gpio_pin_toggle_dt(&led);
	k_msleep(100);
	ret = gpio_pin_toggle_dt(&led);
	k_msleep(100);
	ret = gpio_pin_toggle_dt(&led);




	NVIC_ClearPendingIRQ(TIMER1_IRQn);
	NVIC_EnableIRQ(TIMER1_IRQn); //enable timer1 interrupt
	IRQ_CONNECT(TIMER1_IRQn, 5, TIMER1_IRQHandler, 0, 0); //link interrupt flag to handler

	configure_clock_pin(FREQ_MEASURE_PIN);

	counter_init();
	timer_init();
	gpiote_init(FREQ_MEASURE_PIN); // buttom in SW2
	ppi_gpiote_counter_init();
	ppi_timer_stop_counter_init();
	ppi_timer_start_counter_init();

	//test clock hardware

	gpio_clock_8m(FREQ_MEASURE_PIN);

	//start freq count task
	NRF_TIMER1->TASKS_START = 1;
	gpio_pin_set_dt(&led, 1);



	int old_count = 0;
	while (1) {
		k_msleep(100);
				
				if(old_count != count){
					printf("cc: %dHz\n", count); //report to serial console
					old_count = count;
				}
	}
}