/* * SPDX-FileCopyrightText: 2015-2021 Espressif Systems (Shanghai) CO LTD * * SPDX-License-Identifier: Apache-2.0 */ #include #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 /* ------------------------ 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_12) { 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_12) && (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_12 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); } }