PPI CHANNEL USED TO generate pulse wave

[Fab1223]

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

1. 1ms on and 9ms off.

2. 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

[Fab1223]

means by calling timer start and ppi_enable for first gpio 10ms interrupt. Now i am not getting toggle output. But with BLE i am facing fallowing issue.

1. I cant able to use ppi_enable call in gpio interrupt handler.

2. Always i need to call in BLE interrupt as fallows.

   ppi_enable(); NVIC_EnableIRQ(GPIOTE_IRQn); __enable_irq();

   __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) | (PPI_CHEN_CH3_Msk)| (PPI_CHEN_CH4_Msk));
   
    APP_ERROR_CHECK(err_code);
   

   }

Kindly let me know why i am not able to call ppi_enable in GPIOTE_IRQHandler. if i call i am not getting any PWM.

[Susheel Nuguru]

can you try not using sd_ppi function and enable ppi directly using PPI registers. If it works then something is wrong in softdevice. I am sorry for my late response, i am on vacation and wont be back to work until Monday.

[Fab1223]

Yes i tried by using PPI register directly but that is also not working, for that what i did as fallows.

1. For each ble interuppt i just first_event flag and i set one more flag in gpiote_interrupt handler.
2. i enabled the ppi in main while loop by checking gpio interrupt flag.

Here is my code in BLE.

   for (;;)
    {
				if(pwm_flag == true)
				{
					peripheral_init();
					pwm_flag = false;
				}
				if(nrf_gpio_pin_read(M_BUTTON_PIN) == 0)
				{
					button_config();
					//nrf_delay_ms(50);
				}
        app_sched_execute();
        power_manage();
    }
}

static void peripheral_init()
{
        nrf_gpio_pin_toggle(19);
				gpiote0_timer_dis();
        gpiote_channel_0_set();
        nrf_gpio_pin_clear(AC_OUT_PIN);
				NRF_TIMER2->TASKS_CLEAR=1;
				//pwm_set(2);
				pwm_set(load.slide_value);
				NRF_TIMER2->TASKS_START=1;
			  ppi_enable(); 
}

in BLE interrupt i added fallowing lines.

gpiote_channel_0_set();

										ppi_disable();
										NRF_TIMER2->TASKS_STOP = 1;
										//ppi_enable();
										load.on_off = 1;
										load.slide_value = p_evt_write->data[1];
										OneTime_gpiote_IRQ_f = true;
										NVIC_EnableIRQ(GPIOTE_IRQn);
									__enable_irq();

In gpiote_interrupt handler has fallowing code:

void GPIOTE_IRQHandler(void)
{
		uint32_t             err_code;
    // Event causing the interrupt must be cleared.
     if (NRF_GPIOTE->EVENTS_IN[2] == 1)
    {
			
			if(OneTime_gpiote_IRQ_f == true)
			{
				nrf_gpio_pin_toggle(18);
				pwm_flag=true; 
				OneTime_gpiote_IRQ_f = false;
  			}
			
			NRF_GPIOTE->EVENTS_IN[2] = 0;	
    }
}

I did same logic which is did without BLE, only change is i called pheripheral_init from main in BLE but that i called from GPIOTE_IRQhandler in without BLE.

WIthout BLE if i keep on press the button i am getting constant PWM , there is no invert output.

But with BLE getting inverted ouput some times, and Once you came from vacation , could you tell me what may the issue.

[Susheel Nuguru]

please give me your main.c file Punith, I want to replicate your problem here.

[Fab1223]

Hi Aryan.

You meant to say with BLE main.c right?.