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PPI CHANNEL USED TO generate pulse wave

Hi All,

I am using NRF51822 chip pca10001 development board.

I flashed ble_app_hrs application to the board.

I configure 3 channel for PPI.

static void ppi_init(void)
{
  
  uint32_t err_code;

	 err_code = sd_ppi_channel_assign(0,
                                     &(NRF_TIMER2->EVENTS_COMPARE[0]),
                                     &(NRF_GPIOTE->TASKS_OUT[0]));
    APP_ERROR_CHECK(err_code);
	
		
		err_code = sd_ppi_channel_assign(1,
                                     &(NRF_TIMER2->EVENTS_COMPARE[1]),
                                     &(NRF_GPIOTE->TASKS_OUT[0]));
    APP_ERROR_CHECK(err_code);
	
		err_code = sd_ppi_channel_assign(2,
                                     &(NRF_TIMER2->EVENTS_COMPARE[1]),
                                     &(NRF_TIMER2->TASKS_CLEAR));
    APP_ERROR_CHECK(err_code);
}

I configure gpiote task for channel 0.

void gpiote_channel_0_set(void)
{
	 nrf_gpiote_task_config(0, AC_OUT_PIN, NRF_GPIOTE_POLARITY_TOGGLE, \
                           NRF_GPIOTE_INITIAL_VALUE_HIGH);
}

Now i enable all 3 channels.

__inline void ppi_enable(void)
{
		uint32_t err_code;
		err_code = sd_ppi_channel_enable_set( (PPI_CHEN_CH0_Msk) |  (PPI_CHEN_CH1_Msk)| (PPI_CHEN_CH2_Msk));
    APP_ERROR_CHECK(err_code)
}

The timer2 is intialised as fallows.

static void timer2_init(void)
{
		
   /* Start 16 MHz crystal oscillator */
    NRF_CLOCK->EVENTS_HFCLKSTARTED    = 0;
    NRF_CLOCK->TASKS_HFCLKSTART       = 1;
    /* Wait for the external oscillator to start up */
    while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0)       
    {
        // Do nothing.
    }
		NRF_TIMER2->TASKS_CLEAR = 1;
    NRF_TIMER2->MODE        = TIMER_MODE_MODE_Timer;
		NRF_TIMER2->PRESCALER   = 4;

    /* Load initial values to Timer 2 CC registers */
    /* Set initial CC0 value to anything > 1 */
		NRF_TIMER2->BITMODE   = TIMER_BITMODE_BITMODE_16Bit;
	
}

Now i am updating timer2 cc0 value and cc1 value from BLE characteristic interrupt and then i start the timer.

But for constant cc0 and cc1 value its giving two waveform.

ex- cc0=1000(1ms), cc1=10000(9ms);

i am getting two wave

1ms on and 9ms off.
1ms off and 9ms on.

I need to get only first wave all the time if i write constant value to ble characteristic

Could any one tell me how to solve this?. ( I need to do this with PPI only).

I tried by reinitialising all ppi and gpiote for every ble characteristic interrupt then also it dont work.

Kindly tell me what is the issue.

Regards Punit

Parents

0 Fab1223 over 9 years ago

Hi ALL,

Here i have tried without ble but there also getting inverted ouput .

I also tried for every power reset of the board , i am getting two output.

Here is my code :

    #include <stdbool.h>
#include <stdint.h>
#include "nrf_delay.h"
#include "nrf_gpio.h"
#include "boards.h"
#include "nrf_gpiote.h"

#define AC_OUT_PIN 5
/**
 * @brief Function for application main entry.
 */
 void gpiote0_timer_dis(void)
{
	NRF_GPIOTE->CONFIG[0] = (GPIOTE_CONFIG_MODE_Disabled << GPIOTE_CONFIG_MODE_Pos);
	NRF_GPIOTE->CONFIG[2] = (GPIOTE_CONFIG_MODE_Disabled << GPIOTE_CONFIG_MODE_Pos);
	NRF_TIMER2->TASKS_STOP = 1;
	NVIC_DisableIRQ(GPIOTE_IRQn);
}
void gpiote_channel_0_set(void)
{
	 nrf_gpiote_task_config(0, AC_OUT_PIN, NRF_GPIOTE_POLARITY_TOGGLE, \
                           NRF_GPIOTE_INITIAL_VALUE_HIGH);
}

static void timer2_init(void)
{
		
//   /* Start 16 MHz crystal oscillator */
//    NRF_CLOCK->EVENTS_HFCLKSTARTED    = 0;
//    NRF_CLOCK->TASKS_HFCLKSTART       = 1;
//    /* Wait for the external oscillator to start up */
//    while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0)       
//    {
//        // Do nothing.
//    }
		NRF_TIMER2->TASKS_CLEAR = 1;
    NRF_TIMER2->MODE        = TIMER_MODE_MODE_Timer;
		NRF_TIMER2->PRESCALER   = 4;

    /* Load initial values to Timer 2 CC registers */
    /* Set initial CC0 value to anything > 1 */
  
		NRF_TIMER2->CC[0]       = 8000;//(32);
		//NRF_TIMER2->CC[1] = 10000;//10ms
		NRF_TIMER2->BITMODE   = TIMER_BITMODE_BITMODE_16Bit;
		
   // NRF_TIMER2->SHORTS = (TIMER_SHORTS_COMPARE1_CLEAR_Enabled << TIMER_SHORTS_COMPARE1_CLEAR_Pos);
}
static void ppi_init(void)
{
    // Configure PPI channel 0 to toggle GPIO_OUTPUT_PIN on every TIMER0 COMPARE[0] match (200 ms)
    NRF_PPI->CH[0].EEP = (uint32_t)&NRF_TIMER2->EVENTS_COMPARE[0];
    NRF_PPI->CH[0].TEP = (uint32_t)&NRF_GPIOTE->TASKS_OUT[0];
	
//		NRF_PPI->CH[1].EEP = (uint32_t)&NRF_TIMER2->EVENTS_COMPARE[1];
//    NRF_PPI->CH[1].TEP = (uint32_t)&NRF_GPIOTE->TASKS_OUT[0];

//		NRF_PPI->CH[2].EEP =  (uint32_t)&NRF_TIMER2->EVENTS_COMPARE[1];
//		NRF_PPI->CH[2].TEP =  (uint32_t)&NRF_TIMER2->TASKS_CLEAR;
//    
		NRF_PPI->CH[1].EEP = (uint32_t)&NRF_GPIOTE->EVENTS_IN[2];
    NRF_PPI->CH[1].TEP = (uint32_t)&NRF_GPIOTE->TASKS_OUT[0];

		NRF_PPI->CH[2].EEP =  (uint32_t)&NRF_GPIOTE->EVENTS_IN[2];
		NRF_PPI->CH[2].TEP =  (uint32_t)&NRF_TIMER2->TASKS_CLEAR;
    
                                     
    // Enable PPI channel 0
    NRF_PPI->CHEN = ((PPI_CHEN_CH0_Enabled << PPI_CHEN_CH0_Pos) | (PPI_CHEN_CH1_Enabled << PPI_CHEN_CH1_Pos)|(PPI_CHEN_CH2_Enabled << PPI_CHEN_CH2_Pos));
}

__inline void ppi_enable(void)
{
	NRF_PPI->CHEN = ((PPI_CHEN_CH0_Enabled << PPI_CHEN_CH0_Pos) | (PPI_CHEN_CH1_Enabled << PPI_CHEN_CH1_Pos)|(PPI_CHEN_CH2_Enabled << PPI_CHEN_CH2_Pos));
	
}
__inline static void ppi_disable(void)
{
	NRF_PPI->CHEN = ((PPI_CHEN_CH0_Disabled << PPI_CHEN_CH0_Pos) | (PPI_CHEN_CH1_Disabled << PPI_CHEN_CH1_Pos)|(PPI_CHEN_CH2_Enabled << PPI_CHEN_CH2_Pos));
	
}
static void gpiote_init(void)
{
    // Enable interrupt on input 1 event.
    NRF_GPIOTE->INTENSET = GPIOTE_INTENSET_IN3_Msk |GPIOTE_INTENSET_IN2_Msk;
		nrf_gpiote_event_config(3, 16, NRF_GPIOTE_POLARITY_HITOLO);
		nrf_gpiote_event_config(2, 20, NRF_GPIOTE_POLARITY_LOTOHI);
 
    // Configure GPIOTE channel 0 to generate event on input pin low-to-high transition.
    //nrf_gpiote_event_config(4, 16, NRF_GPIOTE_POLARITY_TOGGLE);
	  NVIC_EnableIRQ(GPIOTE_IRQn);
}


void GPIOTE_IRQHandler(void)
{
	if(NRF_GPIOTE->EVENTS_IN[3]==1)
	{
		nrf_gpio_pin_toggle(18);
		NRF_GPIOTE->EVENTS_IN[3]=0;
		gpiote0_timer_dis();	
		gpiote_channel_0_set();
		gpiote_init();
		timer2_init();
		ppi_init();
		nrf_gpio_pin_clear(AC_OUT_PIN);
		NRF_TIMER2->TASKS_START=1;

	}
	if(NRF_GPIOTE->EVENTS_IN[2]==1)
	{
		nrf_gpio_pin_toggle(19);
		NRF_GPIOTE->EVENTS_IN[2]=0;
	}	
}


int main(void)
{
	nrf_gpio_pin_set(AC_OUT_PIN);
		int i=0;
    // Configure LED-pins as outputs
		nrf_gpio_cfg_input(16,GPIO_PIN_CNF_PULL_Pullup );
		nrf_gpio_cfg_input(17,GPIO_PIN_CNF_PULL_Disabled);
		nrf_gpio_cfg_input(20,GPIO_PIN_CNF_PULL_Disabled);
    nrf_gpio_cfg_output(LED_0);
    nrf_gpio_cfg_output(LED_1);
		nrf_gpio_cfg_output(AC_OUT_PIN);
    nrf_gpio_pin_set(AC_OUT_PIN);
		gpiote_init();	
    // LED 0 and LED 1 blink alternately.
		
	  gpiote_channel_0_set();
		timer2_init();
		ppi_init();
		nrf_gpio_pin_set(AC_OUT_PIN);
		NRF_TIMER2->TASKS_START=1;
		
		while (true)
    {
	
        
    }
}

Here my gpio interrupt(pin 20) is coming for every 10ms.

Since CC0=8000 , i should get always PWM (8ms on and 2ms off). But for every power reset i am getting two PWM. 1.sometime PWM of 2ms on and 8ms off. 2.sometime PWM of 8ms on and 2ms off.

If any one know what will be the issue , kindly let me know the problem.

I need to use PPI only instead of interrupt handler.

Regards Punith

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