Correct use of NRF_LOG for display on Termite

[JK0201]

#include <stdbool.h>    //Permite usar funciones booleanas de C++
#include <stdint.h>     //Permite usar funciones generales de C++

#include "nrf.h"
#include <stdbool.h>   
#include <stdint.h>   

#include "nrf.h"
#include "nordic_common.h"
#include "boards.h"
#include "nrf_gpio.h"
#include "nrf_delay.h"  
#include "nrf_log.h"   

/**
 * @brief Function for application main entry.
 */
int main(void)
{
   nrf_gpio_cfg_input(26, NRF_GPIO_PIN_PULLDOWN);

    while (true)
    { 
				NRF_LOG_INFO(26);
    }
}
/** @} */

Hello to everyone.

I have a doubt about the function of NRF_LOG library in nRF52 DK.
I´m trying to display the voltaje value from pin P0.26 on Termite, so I saw in this page that NRF_LOG_ENABLED and NRF_LOG_BACKEND_UART_ENABLED must be in 1 on sdk_config.h, so that´s ready.
Then I try to use NRF_LOG_INFO() to display the value but I found that NRF_LOG_INFO() it´s only for char parameters.
My question is, does NRF_LOG library has a function to be used with integer value or there´s a way to convert int values into char? (line 20).
This project is the "ble_app_blinky_pca10040_s132", so contains its sdk_config.h file, but I replaced the .c file with one mine.
I hope you can help me.

[Jørgen Holmefjord]

Hi,

If you want to get the state of the pin, you need to read the pin and store its value to a variable. You can then pass the variable to NRF_LOG:

uint32_t pin_state = nrf_gpio_pin_read(26);
NRF_LOG_INFO("Pin state: %d", pin_state);

NRF_LOG use printf format to format the strings.

Best regards,
Jørgen

[Jørgen Holmefjord]

I see that you have not initialized the log module in your application. You need to add this header file to the top of main.c:

#include "nrf_log.h"
#include "nrf_log_ctrl.h"
#include "nrf_log_default_backends.h"

and these lines in start of main-loop:

uint32_t err_code = NRF_LOG_INIT(NULL);
APP_ERROR_CHECK(err_code);

NRF_LOG_DEFAULT_BACKENDS_INIT();

[JK0201]

int main(void)
{
    // Initialize.
    log_init();
    leds_init();
    timers_init();
    buttons_init();
    power_management_init();
    ble_stack_init();
    gap_params_init();
    gatt_init();
    services_init();
    advertising_init();
    conn_params_init();
	
	nrf_gpio_cfg_input(26, NRF_GPIO_PIN_PULLDOWN);
	uint32_t pin_state = nrf_gpio_pin_read(26);

    // Start execution.
    NRF_LOG_INFO("Blinky example started.");
	NRF_LOG_INFO("Pin state: %d", pin_state);
    advertising_start();

    // Enter main loop.
    for (;;)
    {
        idle_state_handle();
    }
}

I´m actually cheking the code with "ble_app_blinky" example, because all the configurations to use LOG are already set, but I can´t make it work. I adjusted the original code with my own lines (16, 17, 21) and only prints the message "Pin state: 0", no matter if I introduce up to 1V of power.

[Jørgen Holmefjord]

You can only read 1 and 0 from the GPIO. The Input high voltage is defined at 0.7 * VDD. If you apply 1 V to the pin, you will not go above this limit, and the state will be low.

[JK0201]

Ok, I understand.
So, I have to put like 3.5V to reach 1, right? because I´m feeding my circuit with 5V.
And, if GPIO only allows me to have 1 and 0, there´s an option to get the real value in voltage?

[JK0201]

I just tried to raise the voltage to 3.5V, but it does not work. I also tried to directly connect a DHT11 temperature and humidity sensor with digital output to the P0.26 pin, but it still prints 0 in Termite. Do I need an extra configuration for being a digital sensor or should it work?

[Jørgen Holmefjord]

You should not set the voltage on a GPIO higher than VDD + 0.3V, as this may break the chip. See Absolute maximum ratings for more details. On the DK, VDD is typically between 2.8-3.0 V. Try connecting the GPIO to VDD on the DK and see if it reads 1.

If you want to measure analog voltages, you need to use the SAADC peripheral. See the SAADC example in the SDK for how to use it.

[JK0201]

No, It doesn´t work.
SAADC is an example to get analog voltages, right? And for digital ones, is there any example? 

[Jørgen Holmefjord]

The SAADC example will give you a digital representation of a analog signal, if you want to measure anything between high (1) and low (0), this is the example you need to use.

If you want to read the digital state of a GPIO (high or low), you can use this example: gpio.zip

By connecting P0.26 to either VDD or GND on the DK, the example will output 1 or 0.

[JK0201]

I´ll try it.
Thank you very much for the support.