mq2 gas sensor
Posted: Tue Apr 05, 2022 4:08 pm
Hello all, I am using an example sketch (adc1_example_main.c) from idf framework. I am using `ADC_CHANNEL_0` (not channel 6 like in sketch) which I presume corresponds to the "VP" pin on the esp32 wroom. I am trying to read the analog output from the mq2 sensor but nothing changes in terms of readings. I get a stagnant "Raw: 4095 Voltage 1063mV" reading from the sketch. The levels drop if i change the pin to an incorrect one so I assume everything is connected properly. Please if anyone might have some insight I would be so thankful!
Code: Untitled.c Select all
/* ADC1 Example
This example code is in the Public Domain (or CC0 licensed, at your option.)
Unless required by applicable law or agreed to in writing, this
software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
CONDITIONS OF ANY KIND, either express or implied.
*/
#include <stdio.h>
#include <stdlib.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/gpio.h"
#include "driver/adc.h"
#include "esp_adc_cal.h"
#define DEFAULT_VREF 1100 //Use adc2_vref_to_gpio() to obtain a better estimate
#define NO_OF_SAMPLES 64 //Multisampling
static esp_adc_cal_characteristics_t *adc_chars;
#if CONFIG_IDF_TARGET_ESP32
static const adc_channel_t channel = ADC_CHANNEL_6; //GPIO34 if ADC1, GPIO14 if ADC2
static const adc_bits_width_t width = ADC_WIDTH_BIT_12;
#elif CONFIG_IDF_TARGET_ESP32S2
static const adc_channel_t channel = ADC_CHANNEL_6; // GPIO7 if ADC1, GPIO17 if ADC2
static const adc_bits_width_t width = ADC_WIDTH_BIT_13;
#endif
static const adc_atten_t atten = ADC_ATTEN_DB_0;
static const adc_unit_t unit = ADC_UNIT_1;
static void check_efuse(void)
{
#if CONFIG_IDF_TARGET_ESP32
//Check if TP is burned into eFuse
if (esp_adc_cal_check_efuse(ESP_ADC_CAL_VAL_EFUSE_TP) == ESP_OK) {
printf("eFuse Two Point: Supported\n");
} else {
printf("eFuse Two Point: NOT supported\n");
}
//Check Vref is burned into eFuse
if (esp_adc_cal_check_efuse(ESP_ADC_CAL_VAL_EFUSE_VREF) == ESP_OK) {
printf("eFuse Vref: Supported\n");
} else {
printf("eFuse Vref: NOT supported\n");
}
#elif CONFIG_IDF_TARGET_ESP32S2
if (esp_adc_cal_check_efuse(ESP_ADC_CAL_VAL_EFUSE_TP) == ESP_OK) {
printf("eFuse Two Point: Supported\n");
} else {
printf("Cannot retrieve eFuse Two Point calibration values. Default calibration values will be used.\n");
}
#else
#error "This example is configured for ESP32/ESP32S2."
#endif
}
static void print_char_val_type(esp_adc_cal_value_t val_type)
{
if (val_type == ESP_ADC_CAL_VAL_EFUSE_TP) {
printf("Characterized using Two Point Value\n");
} else if (val_type == ESP_ADC_CAL_VAL_EFUSE_VREF) {
printf("Characterized using eFuse Vref\n");
} else {
printf("Characterized using Default Vref\n");
}
}
void app_main(void)
{
//Check if Two Point or Vref are burned into eFuse
check_efuse();
//Configure ADC
if (unit == ADC_UNIT_1) {
adc1_config_width(width);
adc1_config_channel_atten(channel, atten);
} else {
adc2_config_channel_atten((adc2_channel_t)channel, atten);
}
//Characterize ADC
adc_chars = calloc(1, sizeof(esp_adc_cal_characteristics_t));
esp_adc_cal_value_t val_type = esp_adc_cal_characterize(unit, atten, width, DEFAULT_VREF, adc_chars);
print_char_val_type(val_type);
//Continuously sample ADC1
while (1) {
uint32_t adc_reading = 0;
//Multisampling
for (int i = 0; i < NO_OF_SAMPLES; i++) {
if (unit == ADC_UNIT_1) {
adc_reading += adc1_get_raw((adc1_channel_t)channel);
} else {
int raw;
adc2_get_raw((adc2_channel_t)channel, width, &raw);
adc_reading += raw;
}
}
adc_reading /= NO_OF_SAMPLES;
//Convert adc_reading to voltage in mV
uint32_t voltage = esp_adc_cal_raw_to_voltage(adc_reading, adc_chars);
printf("Raw: %d\tVoltage: %dmV\n", adc_reading, voltage);
vTaskDelay(pdMS_TO_TICKS(1000));
}
}