OVMS3-idf/examples/peripherals/adc/main/adc1_example_main.c
Darian Leung 88b05f9391 esp_adc_cal: Added ADC calibration component
Added component containg API that is able to correct raw ADC readings
into a voltage in mV. Also provided a helper function that combines
the process of getting the raw ADC1 reading then converting it to a
voltage in mV. In doing so, the adc1_get_voltage() function of the ADC
driver has been deprecated. Instead there is now adc1_get_raw to obtain
the raw ADC1 reading, and adc1_to_voltage() that gets the raw reading
and converts all in one function. Functions using the deprecated
adc1_get_voltage() have also been updated to use adc1_get_raw().

Conversion is based on ADC characteristics. The characteristics are based
on the ADC's v_ref, herefore the appropriate structure and functions have
been provided to obtain the ADC characteristics.

The existing ADC driver has also been modified by adding a function to
route the internal ADC reference voltage to a GPIO allowing users to measure
it manually.

Relevant documentation has also been updated
2017-08-29 18:43:14 +08:00

51 lines
1.6 KiB
C

/* 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 "freertos/queue.h"
#include "driver/gpio.h"
#include "driver/adc.h"
#include "esp_system.h"
#include "esp_adc_cal.h"
/*Note: Different ESP32 modules may have different reference voltages varying from
* 1000mV to 1200mV. Use #define GET_VREF to route v_ref to a GPIO
*/
#define V_REF 1100
#define ADC1_TEST_CHANNEL (ADC1_CHANNEL_6) //GPIO 34
//#define V_REF_TO_GPIO //Remove comment on define to route v_ref to GPIO
void app_main(void)
{
#ifndef V_REF_TO_GPIO
//Init ADC and Characteristics
esp_adc_cal_characteristics_t characteristics;
adc1_config_width(ADC_WIDTH_12Bit);
adc1_config_channel_atten(ADC1_TEST_CHANNEL, ADC_ATTEN_0db);
esp_adc_cal_get_characteristics(V_REF, ADC_ATTEN_0db, ADC_WIDTH_12Bit, &characteristics);
uint32_t voltage;
while(1){
voltage = adc1_to_voltage(ADC1_TEST_CHANNEL, &characteristics);
printf("%d mV\n",voltage);
vTaskDelay(pdMS_TO_TICKS(1000));
}
#else
//Get v_ref
esp_err_t status;
status = adc2_vref_to_gpio(GPIO_NUM_25);
if (status == ESP_OK){
printf("v_ref routed to GPIO\n");
}else{
printf("failed to route v_ref\n");
}
fflush(stdout);
#endif
}