How to program an Analogic output on pin 18

[PhilippeG]

Hello

I have seen in the various examples that most of the time the output are digital (0 or 1) . i program a PWM signal to make any DC output on the pin 18

but unfortunately, this occurs into a loop checking UART data coming. It is simple to let a pin at 0 or 1, but i need to constantly generate the PWM signal if something in between. if i write a while loop in this event handler, i cannot check if there is new data coming since my event handler is stuck doing the PWM. 

How is the best way to turn a pin as an analog output without condamning the event loop to detect if there is a BLE data coming to shut down this signal or modify its value?

Thanks

Philippe

[PhilippeG]

I tried to merge the PWM driver example and the UART one. but i get some issues in SES. these two examples are running perfectly independantly. but i just try to add this very first line of code, adding all the includes missing in the UART examples

static nrf_drv_pwm_t m_pwm0 = NRF_DRV_PWM_INSTANCE(0); 

I added also all the missing c files in the driver and i also get that error. i have no idea where this variable is defined

return NRF_SUCCESS;  (undeclared, first use of this function)

[haakonsh]

It's probably the sdk_config.h files that is missing the settings for the PWM. Di you merge the PWM example into the UART example or the other way around? 

[PhilippeG]

May be the GPIOTE example is the best to merge with the BLE_UARTE? But i would need to add a PWM right. 

Sincerely in all your examples, what it really misses are documentations. Could you please help me understanding what is happening in that code? There is almost no line of documentation.... 

thanks for your understanding. I really want to learn how to manage your product...

#include <stdbool.h>
#include <stdint.h>
#include "nrf.h"
#include "nrf_gpiote.h"
#include "nrf_gpio.h"
#include "boards.h"
#include "nrf_drv_ppi.h"
#include "nrf_drv_timer.h"
#include "nrf_drv_gpiote.h"
#include "app_error.h"

#ifdef BSP_LED_0
#define GPIO_OUTPUT_PIN_NUMBER BSP_LED_0 /**< Pin number for output. */
#endif
#ifndef GPIO_OUTPUT_PIN_NUMBER
#error "Please indicate output pin"
#endif

static nrf_drv_timer_t timer = NRF_DRV_TIMER_INSTANCE(0);

void timer_dummy_handler(nrf_timer_event_t event_type, void * p_context){}

static void led_blinking_setup()
{
uint32_t compare_evt_addr;
uint32_t gpiote_task_addr;
nrf_ppi_channel_t ppi_channel;
ret_code_t err_code;
nrf_drv_gpiote_out_config_t config = GPIOTE_CONFIG_OUT_TASK_TOGGLE(false);

err_code = nrf_drv_gpiote_out_init(GPIO_OUTPUT_PIN_NUMBER, &config);
APP_ERROR_CHECK(err_code);

nrf_drv_timer_extended_compare(&timer, (nrf_timer_cc_channel_t)0, 200 * 1000UL, NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK, false);

err_code = nrf_drv_ppi_channel_alloc(&ppi_channel);
APP_ERROR_CHECK(err_code);

compare_evt_addr = nrf_drv_timer_event_address_get(&timer, NRF_TIMER_EVENT_COMPARE0);
gpiote_task_addr = nrf_drv_gpiote_out_task_addr_get(GPIO_OUTPUT_PIN_NUMBER);

err_code = nrf_drv_ppi_channel_assign(ppi_channel, compare_evt_addr, gpiote_task_addr);
APP_ERROR_CHECK(err_code);

err_code = nrf_drv_ppi_channel_enable(ppi_channel);
APP_ERROR_CHECK(err_code);

nrf_drv_gpiote_out_task_enable(GPIO_OUTPUT_PIN_NUMBER);
}

/**
* @brief Function for application main entry.
*/
int main(void)
{
ret_code_t err_code;

err_code = nrf_drv_ppi_init();
APP_ERROR_CHECK(err_code);

err_code = nrf_drv_gpiote_init();
APP_ERROR_CHECK(err_code);

nrf_drv_timer_config_t timer_cfg = NRF_DRV_TIMER_DEFAULT_CONFIG;
err_code = nrf_drv_timer_init(&timer, &timer_cfg, timer_dummy_handler);
APP_ERROR_CHECK(err_code);
#ifdef NRF51
//Workaround for PAN-73.
*(uint32_t *)0x40008C0C = 1;
#endif

// Setup PPI channel with event from TIMER compare and task GPIOTE pin toggle.
led_blinking_setup();

// Enable timer
nrf_drv_timer_enable(&timer);

while (true)
{
// Do Nothing - GPIO can be toggled without software intervention.
}
}

[haakonsh]

First of it looks to me like your're using an old SDK, I suggest using SDK14.2 if you're a beginner. 

Your main source of documentation is the SDK14.2 API Reference and the nRF52832 Product Specification. The chapter on PPI and EasyDMA are must reads for the nRF5x series of devices. 

I suggest you stick to the peripheral examples until you've managed to create a PWM with a timer and gpiote. I also suggest you try out the SAADC or serial in order to test EasyDMA.

The BLE examples are a bit more complex and I suggest you do not merge a peripheral's example into it until you've understood how the peripheral's example works on its own.

I recommend that you read a peripheral's registers after you've initialized it's driver and compare it to what you'd expect them to be given the registers documentation in the datasheet. It will tell you if you've initialized the driver correctly. 

Last tip; you need to read a peripheral's chapter in the datasheet in order to understand how it's driver is used. 

[PhilippeG]

Hello 

oh great thanks for all your advices. I will follow that. I am using the SDK v15.0

Cheers

Philippe

[haakonsh]

Ahh I was thrown of by the workaround for nRF51. 

[PhilippeG]

Yes i was suprised too to see the nRF51 in that code

I am going to read all the documentation and play with the peripheral examples too. but i am worried about what could be the cause of the problem of behaviour i got today though: i mostly understood the code from gpiote checking the API reference for every line. so i copied and paste the code from main. c into the main.c of the ble_uart (removed all the ble_uart main,c code from that file). which gives me the exact same main.c than the gpiote project in the peripheral. I added the missing c into the driver folder, and made the sdk_config almost identical. 

The Led stayed lighted at High level not blinking i really have the feeling the timer wasnt working. I hope i will be able to figure that problem later after reading the documentation, I have only few days to learn before i have to make that merge working.