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esp-idf/components/esp_adc_cal/esp_adc_cal_esp32.c

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16 KiB
C
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// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include <stdint.h>
#include "esp_types.h"
#include "driver/adc.h"
#include "soc/efuse_periph.h"
#include "esp_err.h"
#include "esp_check.h"
#include "assert.h"
#include "esp_adc_cal.h"
/* ----------------------------- Configuration ------------------------------ */
#ifdef CONFIG_ADC_CAL_EFUSE_TP_ENABLE
#define EFUSE_TP_ENABLED 1
#else
#define EFUSE_TP_ENABLED 0
#endif
#ifdef CONFIG_ADC_CAL_EFUSE_VREF_ENABLE
#define EFUSE_VREF_ENABLED 1
#else
#define EFUSE_VREF_ENABLED 0
#endif
#ifdef CONFIG_ADC_CAL_LUT_ENABLE
#define LUT_ENABLED 1
#else
#define LUT_ENABLED 0
#endif
/* ESP32s with both Two Point Values and Vref burned into eFuse are required to
* also also burn the EFUSE_BLK3_PART_RESERVE flag. A limited set of ESP32s
* (not available through regular sales channel) DO NOT have the
* EFUSE_BLK3_PART_RESERVE burned. Moreover, this set of ESP32s represents Vref
* in Two's Complement format. If this is the case, modify the preprocessor
* definitions below as follows...
* #define CHECK_BLK3_FLAG 0 //Do not check BLK3 flag as it is not burned
* #define VREF_FORMAT 1 //eFuse Vref is in Two's Complement format
*/
#define CHECK_BLK3_FLAG 1
#define VREF_FORMAT 0
/* ------------------------------ eFuse Access ----------------------------- */
#define BLK3_RESERVED_REG EFUSE_BLK0_RDATA3_REG
#define VREF_REG EFUSE_BLK0_RDATA4_REG
#define VREF_MASK 0x1F
#define VREF_STEP_SIZE 7
#define VREF_OFFSET 1100
#define TP_REG EFUSE_BLK3_RDATA3_REG
#define TP_LOW1_OFFSET 278
#define TP_LOW2_OFFSET 421
#define TP_LOW_MASK 0x7F
#define TP_LOW_VOLTAGE 150
#define TP_HIGH1_OFFSET 3265
#define TP_HIGH2_OFFSET 3406
#define TP_HIGH_MASK 0x1FF
#define TP_HIGH_VOLTAGE 850
#define TP_STEP_SIZE 4
/* ----------------------- Raw to Voltage Constants ------------------------- */
#define LIN_COEFF_A_SCALE 65536
#define LIN_COEFF_A_ROUND (LIN_COEFF_A_SCALE/2)
#define LUT_VREF_LOW 1000
#define LUT_VREF_HIGH 1200
#define LUT_ADC_STEP_SIZE 64
#define LUT_POINTS 20
#define LUT_LOW_THRESH 2880
#define LUT_HIGH_THRESH (LUT_LOW_THRESH + LUT_ADC_STEP_SIZE)
#define ADC_12_BIT_RES 4096
const static char LOG_TAG[] = "ADC_CALI";
/* ------------------------ Characterization Constants ---------------------- */
static const uint32_t adc1_tp_atten_scale[4] = {65504, 86975, 120389, 224310};
static const uint32_t adc2_tp_atten_scale[4] = {65467, 86861, 120416, 224708};
static const uint32_t adc1_tp_atten_offset[4] = {0, 1, 27, 54};
static const uint32_t adc2_tp_atten_offset[4] = {0, 9, 26, 66};
static const uint32_t adc1_vref_atten_scale[4] = {57431, 76236, 105481, 196602};
static const uint32_t adc2_vref_atten_scale[4] = {57236, 76175, 105678, 197170};
static const uint32_t adc1_vref_atten_offset[4] = {75, 78, 107, 142};
static const uint32_t adc2_vref_atten_offset[4] = {63, 66, 89, 128};
//20 Point lookup tables, covering ADC readings from 2880 to 4096, step size of 64
static const uint32_t lut_adc1_low[LUT_POINTS] = {2240, 2297, 2352, 2405, 2457, 2512, 2564, 2616, 2664, 2709,
2754, 2795, 2832, 2868, 2903, 2937, 2969, 3000, 3030, 3060};
static const uint32_t lut_adc1_high[LUT_POINTS] = {2667, 2706, 2745, 2780, 2813, 2844, 2873, 2901, 2928, 2956,
2982, 3006, 3032, 3059, 3084, 3110, 3135, 3160, 3184, 3209};
static const uint32_t lut_adc2_low[LUT_POINTS] = {2238, 2293, 2347, 2399, 2451, 2507, 2561, 2613, 2662, 2710,
2754, 2792, 2831, 2869, 2904, 2937, 2968, 2999, 3029, 3059};
static const uint32_t lut_adc2_high[LUT_POINTS] = {2657, 2698, 2738, 2774, 2807, 2838, 2867, 2894, 2921, 2946,
2971, 2996, 3020, 3043, 3067, 3092, 3116, 3139, 3162, 3185};
/* ----------------------- EFuse Access Functions --------------------------- */
static bool check_efuse_vref(void)
{
//Check if Vref is burned in eFuse
return (REG_GET_FIELD(VREF_REG, EFUSE_RD_ADC_VREF) != 0) ? true : false;
}
static bool check_efuse_tp(void)
{
//Check if Two Point values are burned in eFuse
if (CHECK_BLK3_FLAG && (REG_GET_FIELD(BLK3_RESERVED_REG, EFUSE_RD_BLK3_PART_RESERVE) == 0)) {
return false;
}
//All TP cal values must be non zero
if ((REG_GET_FIELD(TP_REG, EFUSE_RD_ADC1_TP_LOW) != 0) &&
(REG_GET_FIELD(TP_REG, EFUSE_RD_ADC2_TP_LOW) != 0) &&
(REG_GET_FIELD(TP_REG, EFUSE_RD_ADC1_TP_HIGH) != 0) &&
(REG_GET_FIELD(TP_REG, EFUSE_RD_ADC2_TP_HIGH) != 0)) {
return true;
} else {
return false;
}
}
static inline int decode_bits(uint32_t bits, uint32_t mask, bool is_twos_compl)
{
int ret;
if (bits & (~(mask >> 1) & mask)) { //Check sign bit (MSB of mask)
//Negative
if (is_twos_compl) {
ret = -(((~bits) + 1) & (mask >> 1)); //2's complement
} else {
ret = -(bits & (mask >> 1)); //Sign-magnitude
}
} else {
//Positive
ret = bits & (mask >> 1);
}
return ret;
}
static uint32_t read_efuse_vref(void)
{
//eFuse stores deviation from ideal reference voltage
uint32_t ret = VREF_OFFSET; //Ideal vref
uint32_t bits = REG_GET_FIELD(VREF_REG, EFUSE_ADC_VREF);
ret += decode_bits(bits, VREF_MASK, VREF_FORMAT) * VREF_STEP_SIZE;
return ret; //ADC Vref in mV
}
static uint32_t read_efuse_tp_low(adc_unit_t adc_num)
{
//ADC reading at 150mV stored in two's complement format
uint32_t ret;
uint32_t bits;
if (adc_num == ADC_UNIT_1) {
ret = TP_LOW1_OFFSET;
bits = REG_GET_FIELD(TP_REG, EFUSE_RD_ADC1_TP_LOW);
} else {
ret = TP_LOW2_OFFSET;
bits = REG_GET_FIELD(TP_REG, EFUSE_RD_ADC2_TP_LOW);
}
ret += decode_bits(bits, TP_LOW_MASK, true) * TP_STEP_SIZE;
return ret; //Reading of ADC at 150mV
}
static uint32_t read_efuse_tp_high(adc_unit_t adc_num)
{
//ADC reading at 850mV stored in two's complement format
uint32_t ret;
uint32_t bits;
if (adc_num == ADC_UNIT_1) {
ret = TP_HIGH1_OFFSET;
bits = REG_GET_FIELD(TP_REG, EFUSE_RD_ADC1_TP_HIGH);
} else {
ret = TP_HIGH2_OFFSET;
bits = REG_GET_FIELD(TP_REG, EFUSE_RD_ADC2_TP_HIGH);
}
ret += decode_bits(bits, TP_HIGH_MASK, true) * TP_STEP_SIZE;
return ret; //Reading of ADC at 850mV
}
/* ----------------------- Characterization Functions ----------------------- */
static void characterize_using_two_point(adc_unit_t adc_num,
adc_atten_t atten,
uint32_t high,
uint32_t low,
uint32_t *coeff_a,
uint32_t *coeff_b)
{
const uint32_t *atten_scales;
const uint32_t *atten_offsets;
if (adc_num == ADC_UNIT_1) { //Using ADC 1
atten_scales = adc1_tp_atten_scale;
atten_offsets = adc1_tp_atten_offset;
} else { //Using ADC 2
atten_scales = adc2_tp_atten_scale;
atten_offsets = adc2_tp_atten_offset;
}
//Characterize ADC-Voltage curve as y = (coeff_a * x) + coeff_b
uint32_t delta_x = high - low;
uint32_t delta_v = TP_HIGH_VOLTAGE - TP_LOW_VOLTAGE;
//Where coeff_a = (delta_v/delta_x) * atten_scale
*coeff_a = (delta_v * atten_scales[atten] + (delta_x / 2)) / delta_x; //+(delta_x/2) for rounding
//Where coeff_b = high_v - ((delta_v/delta_x) * high_x) + atten_offset
*coeff_b = TP_HIGH_VOLTAGE - ((delta_v * high + (delta_x / 2)) / delta_x) + atten_offsets[atten];
}
static void characterize_using_vref(adc_unit_t adc_num,
adc_atten_t atten,
uint32_t vref,
uint32_t *coeff_a,
uint32_t *coeff_b)
{
const uint32_t *atten_scales;
const uint32_t *atten_offsets;
if (adc_num == ADC_UNIT_1) { //Using ADC 1
atten_scales = adc1_vref_atten_scale;
atten_offsets = adc1_vref_atten_offset;
} else { //Using ADC 2
atten_scales = adc2_vref_atten_scale;
atten_offsets = adc2_vref_atten_offset;
}
//Characterize ADC-Voltage curve as y = (coeff_a * x) + coeff_b
//Where coeff_a = (vref/4096) * atten_scale
*coeff_a = (vref * atten_scales[atten]) / (ADC_12_BIT_RES);
*coeff_b = atten_offsets[atten];
}
/* ------------------------ Conversion Functions --------------------------- */
static uint32_t calculate_voltage_linear(uint32_t adc_reading, uint32_t coeff_a, uint32_t coeff_b)
{
//Where voltage = coeff_a * adc_reading + coeff_b
return (((coeff_a * adc_reading) + LIN_COEFF_A_ROUND) / LIN_COEFF_A_SCALE) + coeff_b;
}
//Only call when ADC reading is above threshold
static uint32_t calculate_voltage_lut(uint32_t adc, uint32_t vref, const uint32_t *low_vref_curve, const uint32_t *high_vref_curve)
{
//Get index of lower bound points of LUT
uint32_t i = (adc - LUT_LOW_THRESH) / LUT_ADC_STEP_SIZE;
//Let the X Axis be Vref, Y axis be ADC reading, and Z be voltage
int x2dist = LUT_VREF_HIGH - vref; //(x2 - x)
int x1dist = vref - LUT_VREF_LOW; //(x - x1)
int y2dist = ((i + 1) * LUT_ADC_STEP_SIZE) + LUT_LOW_THRESH - adc; //(y2 - y)
int y1dist = adc - ((i * LUT_ADC_STEP_SIZE) + LUT_LOW_THRESH); //(y - y1)
//For points for bilinear interpolation
int q11 = low_vref_curve[i]; //Lower bound point of low_vref_curve
int q12 = low_vref_curve[i + 1]; //Upper bound point of low_vref_curve
int q21 = high_vref_curve[i]; //Lower bound point of high_vref_curve
int q22 = high_vref_curve[i + 1]; //Upper bound point of high_vref_curve
//Bilinear interpolation
//Where z = 1/((x2-x1)*(y2-y1)) * ( (q11*x2dist*y2dist) + (q21*x1dist*y2dist) + (q12*x2dist*y1dist) + (q22*x1dist*y1dist) )
int voltage = (q11 * x2dist * y2dist) + (q21 * x1dist * y2dist) + (q12 * x2dist * y1dist) + (q22 * x1dist * y1dist);
voltage += ((LUT_VREF_HIGH - LUT_VREF_LOW) * LUT_ADC_STEP_SIZE) / 2; //Integer division rounding
voltage /= ((LUT_VREF_HIGH - LUT_VREF_LOW) * LUT_ADC_STEP_SIZE); //Divide by ((x2-x1)*(y2-y1))
return (uint32_t)voltage;
}
static inline uint32_t interpolate_two_points(uint32_t y1, uint32_t y2, uint32_t x_step, uint32_t x)
{
//Interpolate between two points (x1,y1) (x2,y2) between 'lower' and 'upper' separated by 'step'
return ((y1 * x_step) + (y2 * x) - (y1 * x) + (x_step / 2)) / x_step;
}
/* ------------------------- Public API ------------------------------------- */
esp_err_t esp_adc_cal_check_efuse(esp_adc_cal_value_t source)
{
if (source == ESP_ADC_CAL_VAL_EFUSE_TP) {
return (check_efuse_tp()) ? ESP_OK : ESP_ERR_NOT_SUPPORTED;
} else if (source == ESP_ADC_CAL_VAL_EFUSE_VREF) {
return (check_efuse_vref()) ? ESP_OK : ESP_ERR_NOT_SUPPORTED;
} else {
return ESP_ERR_INVALID_ARG;
}
}
esp_adc_cal_value_t esp_adc_cal_characterize(adc_unit_t adc_num,
adc_atten_t atten,
adc_bits_width_t bit_width,
uint32_t default_vref,
esp_adc_cal_characteristics_t *chars)
{
//Check parameters
assert((adc_num == ADC_UNIT_1) || (adc_num == ADC_UNIT_2));
assert(chars != NULL);
assert(bit_width < ADC_WIDTH_MAX);
//Check eFuse if enabled to do so
bool efuse_tp_present = check_efuse_tp();
bool efuse_vref_present = check_efuse_vref();
esp_adc_cal_value_t ret;
if (efuse_tp_present && EFUSE_TP_ENABLED) {
//Characterize based on Two Point values
uint32_t high = read_efuse_tp_high(adc_num);
uint32_t low = read_efuse_tp_low(adc_num);
characterize_using_two_point(adc_num, atten, high, low, &chars->coeff_a, &chars->coeff_b);
ret = ESP_ADC_CAL_VAL_EFUSE_TP;
} else if (efuse_vref_present && EFUSE_VREF_ENABLED) {
//Characterize based on eFuse Vref
uint32_t vref = read_efuse_vref();
characterize_using_vref(adc_num, atten, vref, &chars->coeff_a, &chars->coeff_b);
ret = ESP_ADC_CAL_VAL_EFUSE_VREF;
} else {
//Characterized based on default Vref
characterize_using_vref(adc_num, atten, default_vref, &chars->coeff_a, &chars->coeff_b);
ret = ESP_ADC_CAL_VAL_DEFAULT_VREF;
}
//Initialized remaining fields
chars->adc_num = adc_num;
chars->atten = atten;
chars->bit_width = bit_width;
chars->vref = (EFUSE_VREF_ENABLED && efuse_vref_present) ? read_efuse_vref() : default_vref;
//Initialize fields for lookup table if necessary
if (LUT_ENABLED && atten == ADC_ATTEN_DB_11) {
chars->low_curve = (adc_num == ADC_UNIT_1) ? lut_adc1_low : lut_adc2_low;
chars->high_curve = (adc_num == ADC_UNIT_1) ? lut_adc1_high : lut_adc2_high;
} else {
chars->low_curve = NULL;
chars->high_curve = NULL;
}
return ret;
}
uint32_t esp_adc_cal_raw_to_voltage(uint32_t adc_reading, const esp_adc_cal_characteristics_t *chars)
{
assert(chars != NULL);
//Scale adc_rading if not 12 bits wide
adc_reading = (adc_reading << (ADC_WIDTH_BIT_12 - chars->bit_width));
if (adc_reading > ADC_12_BIT_RES - 1) {
adc_reading = ADC_12_BIT_RES - 1; //Set to 12bit res max
}
if (LUT_ENABLED && (chars->atten == ADC_ATTEN_DB_11) && (adc_reading >= LUT_LOW_THRESH)) { //Check if in non-linear region
//Use lookup table to get voltage in non linear portion of ADC_ATTEN_DB_11
uint32_t lut_voltage = calculate_voltage_lut(adc_reading, chars->vref, chars->low_curve, chars->high_curve);
if (adc_reading <= LUT_HIGH_THRESH) { //If ADC is transitioning from linear region to non-linear region
//Linearly interpolate between linear voltage and lut voltage
uint32_t linear_voltage = calculate_voltage_linear(adc_reading, chars->coeff_a, chars->coeff_b);
return interpolate_two_points(linear_voltage, lut_voltage, LUT_ADC_STEP_SIZE, (adc_reading - LUT_LOW_THRESH));
} else {
return lut_voltage;
}
} else {
return calculate_voltage_linear(adc_reading, chars->coeff_a, chars->coeff_b);
}
}
esp_err_t esp_adc_cal_get_voltage(adc_channel_t channel,
const esp_adc_cal_characteristics_t *chars,
uint32_t *voltage)
{
//Check parameters
ESP_RETURN_ON_FALSE(chars != NULL, ESP_ERR_INVALID_ARG, LOG_TAG, "No characteristic input");
ESP_RETURN_ON_FALSE(voltage != NULL, ESP_ERR_INVALID_ARG, LOG_TAG, "No output buffer");
esp_err_t ret = ESP_OK;
int adc_reading;
if (chars->adc_num == ADC_UNIT_1) {
//Check channel is valid on ADC1
ESP_RETURN_ON_FALSE(channel < SOC_ADC_CHANNEL_NUM(0), ESP_ERR_INVALID_ARG, LOG_TAG, "Invalid channel");
adc_reading = adc1_get_raw(channel);
} else {
//Check channel is valid on ADC2
ESP_RETURN_ON_FALSE(channel < SOC_ADC_CHANNEL_NUM(1), ESP_ERR_INVALID_ARG, LOG_TAG, "Invalid channel");
ret = adc2_get_raw(channel, chars->bit_width, &adc_reading);
}
*voltage = esp_adc_cal_raw_to_voltage((uint32_t)adc_reading, chars);
return ret;
}
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