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ADC drivers for esp32 #7

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998a702
ADC drivers for esp32
YVishere Apr 27, 2025
9e8f34c
Undid ADC2 width hardcoding
YVishere Apr 27, 2025
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109 changes: 109 additions & 0 deletions adc_esp/adc_esp.cpp
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#include "adc_esp.h"
#include <string.h>

// Calibration characteristics
static esp_adc_cal_characteristics_t adc_chars;

adc_bits_width_t adc2_width = ADC_WIDTH_BIT_12; // Since ADC2 can't be configured directly, we set the width here

esp_err_t esp32_adc_init(ESP32_ADC_Config* config) {
esp_err_t ret = ESP_OK;

// Configure ADC unit
if (config->unit == ADC_UNIT_1) {
ret = adc1_config_width(config->width);
if (ret != ESP_OK) return ret;
}
else if (config->unit == ADC_UNIT_2) {
adc2_width = config->width;
} else {
return ESP_ERR_INVALID_ARG;
}

// Characterize ADC for calibration
esp_adc_cal_characterize(config->unit, config->attenuation,
config->width, config->vref, &adc_chars);

return ESP_OK;
}

esp_err_t esp32_adc_config_channel(adc_unit_t unit, adc_channel_t channel, adc_atten_t attenuation) {
if (unit == ADC_UNIT_1) {
return adc1_config_channel_atten((adc1_channel_t)channel, attenuation);
} else if (unit == ADC_UNIT_2) {
return adc2_config_channel_atten((adc2_channel_t)channel, attenuation);
}
return ESP_ERR_INVALID_ARG;
}

int esp32_adc_read_voltage(adc_unit_t unit, adc_channel_t channel, ESP32_ADC_Config* config) {
int raw_value = esp32_adc_read_raw(unit, channel);
if (raw_value < 0) return -1;

// Convert raw value to voltage
uint32_t voltage = esp_adc_cal_raw_to_voltage(raw_value, &adc_chars);
return voltage;
}

int esp32_adc_read_raw(adc_unit_t unit, adc_channel_t channel) {
int raw_value;

if (unit == ADC_UNIT_1) {
// Configure the channel attenuation if not already done
// This should ideally be done during initialization for each channel
adc1_channel_t adc1_channel = (adc1_channel_t)channel;
raw_value = adc1_get_raw(adc1_channel);
} else if (unit == ADC_UNIT_2) {
// ADC2 can't be used when Wi-Fi is active
esp_err_t ret = adc2_get_raw((adc2_channel_t)channel, adc2_width, &raw_value);
if (ret != ESP_OK) {
return -1;
}
} else {
return -1; // Invalid ADC unit
}

return raw_value;
}

float esp32_adc_normalize(int raw_value, ESP32_ADC_Config* config) {
if (raw_value < 0) return -1.0f;

int max_value;
switch (config->width) {
case ADC_WIDTH_BIT_9: max_value = 511; break;
case ADC_WIDTH_BIT_10: max_value = 1023; break;
case ADC_WIDTH_BIT_11: max_value = 2047; break;
case ADC_WIDTH_BIT_12: max_value = 4095; break;
default: return -1.0f;
}

return (float)raw_value / max_value;
}

esp_err_t esp32_adc_gpio_to_channel(int gpio_pin, adc_unit_t* unit, adc_channel_t* channel) {
// Map GPIO pin to ADC channel
// ADC1 channels
if (gpio_pin == 36) { *unit = ADC_UNIT_1; *channel = (adc_channel_t)ADC1_CHANNEL_0; return ESP_OK; }
if (gpio_pin == 37) { *unit = ADC_UNIT_1; *channel = (adc_channel_t)ADC1_CHANNEL_1; return ESP_OK; }
if (gpio_pin == 38) { *unit = ADC_UNIT_1; *channel = (adc_channel_t)ADC1_CHANNEL_2; return ESP_OK; }
if (gpio_pin == 39) { *unit = ADC_UNIT_1; *channel = (adc_channel_t)ADC1_CHANNEL_3; return ESP_OK; }
if (gpio_pin == 32) { *unit = ADC_UNIT_1; *channel = (adc_channel_t)ADC1_CHANNEL_4; return ESP_OK; }
if (gpio_pin == 33) { *unit = ADC_UNIT_1; *channel = (adc_channel_t)ADC1_CHANNEL_5; return ESP_OK; }
if (gpio_pin == 34) { *unit = ADC_UNIT_1; *channel = (adc_channel_t)ADC1_CHANNEL_6; return ESP_OK; }
if (gpio_pin == 35) { *unit = ADC_UNIT_1; *channel = (adc_channel_t)ADC1_CHANNEL_7; return ESP_OK; }

// ADC2 channels
if (gpio_pin == 4) { *unit = ADC_UNIT_2; *channel = (adc_channel_t)ADC2_CHANNEL_0; return ESP_OK; }
if (gpio_pin == 0) { *unit = ADC_UNIT_2; *channel = (adc_channel_t)ADC2_CHANNEL_1; return ESP_OK; }
if (gpio_pin == 2) { *unit = ADC_UNIT_2; *channel = (adc_channel_t)ADC2_CHANNEL_2; return ESP_OK; }
if (gpio_pin == 15) { *unit = ADC_UNIT_2; *channel = (adc_channel_t)ADC2_CHANNEL_3; return ESP_OK; }
if (gpio_pin == 13) { *unit = ADC_UNIT_2; *channel = (adc_channel_t)ADC2_CHANNEL_4; return ESP_OK; }
if (gpio_pin == 12) { *unit = ADC_UNIT_2; *channel = (adc_channel_t)ADC2_CHANNEL_5; return ESP_OK; }
if (gpio_pin == 14) { *unit = ADC_UNIT_2; *channel = (adc_channel_t)ADC2_CHANNEL_6; return ESP_OK; }
if (gpio_pin == 27) { *unit = ADC_UNIT_2; *channel = (adc_channel_t)ADC2_CHANNEL_7; return ESP_OK; }
if (gpio_pin == 25) { *unit = ADC_UNIT_2; *channel = (adc_channel_t)ADC2_CHANNEL_8; return ESP_OK; }
if (gpio_pin == 26) { *unit = ADC_UNIT_2; *channel = (adc_channel_t)ADC2_CHANNEL_9; return ESP_OK; }

return ESP_ERR_NOT_FOUND;
}
65 changes: 65 additions & 0 deletions adc_esp/adc_esp.h
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#ifndef ESP32_ADC_H
#define ESP32_ADC_H

#include <driver/adc.h>
#include <esp_adc_cal.h>

// ADC configuration struct
typedef struct {
adc_unit_t unit; // ADC unit (ADC1 or ADC2)
adc_bits_width_t width; // ADC bit width (9-12 bits)
adc_atten_t attenuation; // ADC attenuation
uint32_t vref; // Reference voltage in mV (typically 1100mV)
} ESP32_ADC_Config;

/**
* Initialize ADC with the given configuration
* @param config ADC configuration
* @return ESP_OK on success, error code otherwise
*/
esp_err_t esp32_adc_init(ESP32_ADC_Config* config);

/**
* Configure a specific ADC channel with the given attenuation
* @param unit ADC unit (ADC1 or ADC2)
* @param channel ADC channel
* @param attenuation Attenuation level
* @return ESP_OK on success, error code otherwise
*/
esp_err_t esp32_adc_config_channel(adc_unit_t unit, adc_channel_t channel, adc_atten_t attenuation);

/**
* Read ADC value from the specified channel
* @param unit ADC unit (ADC1 or ADC2)
* @param channel ADC channel
* @param config ADC configuration used for calibration
* @return Voltage in millivolts, or -1 on error
*/
int esp32_adc_read_voltage(adc_unit_t unit, adc_channel_t channel, ESP32_ADC_Config* config);

/**
* Read raw ADC value from the specified channel
* @param unit ADC unit (ADC1 or ADC2)
* @param channel ADC channel
* @return Raw ADC value (0-4095 for 12-bit), or -1 on error
*/
int esp32_adc_read_raw(adc_unit_t unit, adc_channel_t channel);

/**
* Convert raw ADC value to normalized float (0.0-1.0)
* @param raw_value Raw ADC value
* @param config ADC configuration for bit width
* @return Normalized value between 0.0 and 1.0
*/
float esp32_adc_normalize(int raw_value, ESP32_ADC_Config* config);

/**
* Get ADC channel for a GPIO pin
* @param gpio_pin GPIO pin number
* @param unit Pointer to store the ADC unit
* @param channel Pointer to store the ADC channel
* @return ESP_OK if mapping successful, error code otherwise
*/
esp_err_t esp32_adc_gpio_to_channel(int gpio_pin, adc_unit_t* unit, adc_channel_t* channel);

#endif // ESP32_ADC_H