ESP32 Forum

Posted: **Fri Apr 12, 2019 2:39 pm**

<r>I could not understanding why ESP-IDF voltage calculation if apply to convert the raw reading from GPIO39 would result in crash
 
uint32_t voltage = esp_adc_cal_raw_to_voltage(read_raw, adc_chars); 
 
Below is the simple source code

Code: Untitled.c Select all

#include <stdio.h><br/>

#include <stdlib.h><br/>

#include "freertos/FreeRTOS.h"<br/>

#include "freertos/task.h"<br/>

#include "freertos/queue.h"<br/>

#include "driver/gpio.h"<br/>

#include "driver/adc.h"<br/>

#include "driver/dac.h"<br/>

#include "esp_system.h"<br/>

#include "esp_adc_cal.h"<br/>

#define BLINK_GPIO 2

<br/>

<br/>

static void Read_GPIO39() {<br/>

    int read_raw = 0;<br/>

    adc1_config_width(ADC_WIDTH_BIT_12);<br/>

    adc1_config_channel_atten(ADC1_CHANNEL_3, ADC_ATTEN_DB_11);<br/>

    read_raw=adc1_get_raw(ADC1_CHANNEL_3);<br/>

    **//uint32_t voltage = esp_adc_cal_raw_to_voltage(read_raw, adc_chars);**<br/>

    printf("Intensity : %d\n", read_raw);<br/>

<br/>

    //printf("Voltage: %d\n", voltage);<br/>

    gpio_pad_select_gpio(BLINK_GPIO);<br/>

    gpio_set_direction(BLINK_GPIO, GPIO_MODE_OUTPUT);<br/>

    gpio_set_level(BLINK_GPIO, 1);<br/>

}<br/>

<br/>

<br/>

void app_main() {<br/>

    ESP_ERROR_CHECK(nvs_flash_init());<br/>

    // initialise_wifi();<br/>

    while (1) {<br/>

        Read_GPIO39();<br/>

<br/>

        vTaskDelay(3000 / portTICK_PERIOD_MS);<br/>

        gpio_set_level(BLINK_GPIO, 0);<br/>

}<br/>

}

Posted: **Mon Apr 15, 2019 3:34 am**

What is adc_chars? How did you define it?

Posted: **Mon Apr 15, 2019 11:40 am**

with below statement , 7% variance is observed. I have doubt on the atten not sure should this be ADC_ATTEN_DB_11 or some others value for GPIO39 , voltage reading is very unstable on genuine espressif dev Wrover B development board

static const adc_atten_t atten = ADC_ATTEN_DB_11;
static const adc_unit_t unit = ADC_UNIT_1;
#define DEFAULT_VREF 1100
adc_chars = calloc(1, sizeof(esp_adc_cal_characteristics_t));

esp_adc_cal_characterize(unit, atten, ADC_WIDTH_BIT_12, DEFAULT_VREF,adc_chars);

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convert raw reading from GPIO39 to voltage would result in crash

convert raw reading from GPIO39 to voltage would result in crash

Re: convert raw reading from GPIO39 to voltage would result in crash

Re: convert raw reading from GPIO39 to voltage would result in crash