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355 lines
15 KiB
C
355 lines
15 KiB
C
/*
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* SPDX-FileCopyrightText: 2015-2021 Espressif Systems (Shanghai) CO LTD
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <stdint.h>
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#include "esp_types.h"
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#include "driver/adc.h"
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#include "soc/efuse_periph.h"
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#include "esp_err.h"
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#include "assert.h"
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#include "esp_adc_cal.h"
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/* ----------------------------- Configuration ------------------------------ */
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#ifdef CONFIG_ADC_CAL_EFUSE_TP_ENABLE
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#define EFUSE_TP_ENABLED 1
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#else
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#define EFUSE_TP_ENABLED 0
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#endif
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#ifdef CONFIG_ADC_CAL_EFUSE_VREF_ENABLE
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#define EFUSE_VREF_ENABLED 1
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#else
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#define EFUSE_VREF_ENABLED 0
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#endif
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#ifdef CONFIG_ADC_CAL_LUT_ENABLE
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#define LUT_ENABLED 1
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#else
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#define LUT_ENABLED 0
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#endif
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/* ESP32s with both Two Point Values and Vref burned into eFuse are required to
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* also also burn the EFUSE_BLK3_PART_RESERVE flag. A limited set of ESP32s
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* (not available through regular sales channel) DO NOT have the
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* EFUSE_BLK3_PART_RESERVE burned. Moreover, this set of ESP32s represents Vref
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* in Two's Complement format. If this is the case, modify the preprocessor
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* definitions below as follows...
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* #define CHECK_BLK3_FLAG 0 //Do not check BLK3 flag as it is not burned
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* #define VREF_FORMAT 1 //eFuse Vref is in Two's Complement format
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*/
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#define CHECK_BLK3_FLAG 1
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#define VREF_FORMAT 0
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/* ------------------------------ eFuse Access ----------------------------- */
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#define BLK3_RESERVED_REG EFUSE_BLK0_RDATA3_REG
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#define VREF_REG EFUSE_BLK0_RDATA4_REG
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#define VREF_MASK 0x1F
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#define VREF_STEP_SIZE 7
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#define VREF_OFFSET 1100
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#define TP_REG EFUSE_BLK3_RDATA3_REG
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#define TP_LOW1_OFFSET 278
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#define TP_LOW2_OFFSET 421
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#define TP_LOW_MASK 0x7F
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#define TP_LOW_VOLTAGE 150
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#define TP_HIGH1_OFFSET 3265
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#define TP_HIGH2_OFFSET 3406
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#define TP_HIGH_MASK 0x1FF
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#define TP_HIGH_VOLTAGE 850
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#define TP_STEP_SIZE 4
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/* ----------------------- Raw to Voltage Constants ------------------------- */
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#define LIN_COEFF_A_SCALE 65536
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#define LIN_COEFF_A_ROUND (LIN_COEFF_A_SCALE/2)
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#define LUT_VREF_LOW 1000
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#define LUT_VREF_HIGH 1200
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#define LUT_ADC_STEP_SIZE 64
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#define LUT_POINTS 20
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#define LUT_LOW_THRESH 2880
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#define LUT_HIGH_THRESH (LUT_LOW_THRESH + LUT_ADC_STEP_SIZE)
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#define ADC_12_BIT_RES 4096
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/* ------------------------ Characterization Constants ---------------------- */
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static const uint32_t adc1_tp_atten_scale[4] = {65504, 86975, 120389, 224310};
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static const uint32_t adc2_tp_atten_scale[4] = {65467, 86861, 120416, 224708};
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static const uint32_t adc1_tp_atten_offset[4] = {0, 1, 27, 54};
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static const uint32_t adc2_tp_atten_offset[4] = {0, 9, 26, 66};
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static const uint32_t adc1_vref_atten_scale[4] = {57431, 76236, 105481, 196602};
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static const uint32_t adc2_vref_atten_scale[4] = {57236, 76175, 105678, 197170};
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static const uint32_t adc1_vref_atten_offset[4] = {75, 78, 107, 142};
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static const uint32_t adc2_vref_atten_offset[4] = {63, 66, 89, 128};
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//20 Point lookup tables, covering ADC readings from 2880 to 4096, step size of 64
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static const uint32_t lut_adc1_low[LUT_POINTS] = {2240, 2297, 2352, 2405, 2457, 2512, 2564, 2616, 2664, 2709,
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2754, 2795, 2832, 2868, 2903, 2937, 2969, 3000, 3030, 3060};
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static const uint32_t lut_adc1_high[LUT_POINTS] = {2667, 2706, 2745, 2780, 2813, 2844, 2873, 2901, 2928, 2956,
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2982, 3006, 3032, 3059, 3084, 3110, 3135, 3160, 3184, 3209};
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static const uint32_t lut_adc2_low[LUT_POINTS] = {2238, 2293, 2347, 2399, 2451, 2507, 2561, 2613, 2662, 2710,
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2754, 2792, 2831, 2869, 2904, 2937, 2968, 2999, 3029, 3059};
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static const uint32_t lut_adc2_high[LUT_POINTS] = {2657, 2698, 2738, 2774, 2807, 2838, 2867, 2894, 2921, 2946,
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2971, 2996, 3020, 3043, 3067, 3092, 3116, 3139, 3162, 3185};
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/* ----------------------- EFuse Access Functions --------------------------- */
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static bool check_efuse_vref(void)
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{
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//Check if Vref is burned in eFuse
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return (REG_GET_FIELD(VREF_REG, EFUSE_RD_ADC_VREF) != 0) ? true : false;
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}
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static bool check_efuse_tp(void)
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{
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//Check if Two Point values are burned in eFuse
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if (CHECK_BLK3_FLAG && (REG_GET_FIELD(BLK3_RESERVED_REG, EFUSE_RD_BLK3_PART_RESERVE) == 0)) {
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return false;
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}
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//All TP cal values must be non zero
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if ((REG_GET_FIELD(TP_REG, EFUSE_RD_ADC1_TP_LOW) != 0) &&
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(REG_GET_FIELD(TP_REG, EFUSE_RD_ADC2_TP_LOW) != 0) &&
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(REG_GET_FIELD(TP_REG, EFUSE_RD_ADC1_TP_HIGH) != 0) &&
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(REG_GET_FIELD(TP_REG, EFUSE_RD_ADC2_TP_HIGH) != 0)) {
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return true;
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} else {
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return false;
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}
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}
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static inline int decode_bits(uint32_t bits, uint32_t mask, bool is_twos_compl)
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{
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int ret;
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if (bits & (~(mask >> 1) & mask)) { //Check sign bit (MSB of mask)
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//Negative
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if (is_twos_compl) {
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ret = -(((~bits) + 1) & (mask >> 1)); //2's complement
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} else {
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ret = -(bits & (mask >> 1)); //Sign-magnitude
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}
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} else {
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//Positive
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ret = bits & (mask >> 1);
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}
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return ret;
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}
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static uint32_t read_efuse_vref(void)
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{
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//eFuse stores deviation from ideal reference voltage
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uint32_t ret = VREF_OFFSET; //Ideal vref
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uint32_t bits = REG_GET_FIELD(VREF_REG, EFUSE_ADC_VREF);
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ret += decode_bits(bits, VREF_MASK, VREF_FORMAT) * VREF_STEP_SIZE;
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return ret; //ADC Vref in mV
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}
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static uint32_t read_efuse_tp_low(adc_unit_t adc_num)
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{
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//ADC reading at 150mV stored in two's complement format
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uint32_t ret;
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uint32_t bits;
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if (adc_num == ADC_UNIT_1) {
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ret = TP_LOW1_OFFSET;
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bits = REG_GET_FIELD(TP_REG, EFUSE_RD_ADC1_TP_LOW);
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} else {
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ret = TP_LOW2_OFFSET;
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bits = REG_GET_FIELD(TP_REG, EFUSE_RD_ADC2_TP_LOW);
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}
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ret += decode_bits(bits, TP_LOW_MASK, true) * TP_STEP_SIZE;
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return ret; //Reading of ADC at 150mV
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}
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static uint32_t read_efuse_tp_high(adc_unit_t adc_num)
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{
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//ADC reading at 850mV stored in two's complement format
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uint32_t ret;
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uint32_t bits;
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if (adc_num == ADC_UNIT_1) {
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ret = TP_HIGH1_OFFSET;
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bits = REG_GET_FIELD(TP_REG, EFUSE_RD_ADC1_TP_HIGH);
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} else {
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ret = TP_HIGH2_OFFSET;
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bits = REG_GET_FIELD(TP_REG, EFUSE_RD_ADC2_TP_HIGH);
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}
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ret += decode_bits(bits, TP_HIGH_MASK, true) * TP_STEP_SIZE;
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return ret; //Reading of ADC at 850mV
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}
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/* ----------------------- Characterization Functions ----------------------- */
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static void characterize_using_two_point(adc_unit_t adc_num,
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adc_atten_t atten,
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uint32_t high,
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uint32_t low,
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uint32_t *coeff_a,
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uint32_t *coeff_b)
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{
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const uint32_t *atten_scales;
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const uint32_t *atten_offsets;
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if (adc_num == ADC_UNIT_1) { //Using ADC 1
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atten_scales = adc1_tp_atten_scale;
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atten_offsets = adc1_tp_atten_offset;
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} else { //Using ADC 2
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atten_scales = adc2_tp_atten_scale;
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atten_offsets = adc2_tp_atten_offset;
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}
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//Characterize ADC-Voltage curve as y = (coeff_a * x) + coeff_b
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uint32_t delta_x = high - low;
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uint32_t delta_v = TP_HIGH_VOLTAGE - TP_LOW_VOLTAGE;
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//Where coeff_a = (delta_v/delta_x) * atten_scale
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*coeff_a = (delta_v * atten_scales[atten] + (delta_x / 2)) / delta_x; //+(delta_x/2) for rounding
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//Where coeff_b = high_v - ((delta_v/delta_x) * high_x) + atten_offset
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*coeff_b = TP_HIGH_VOLTAGE - ((delta_v * high + (delta_x / 2)) / delta_x) + atten_offsets[atten];
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}
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static void characterize_using_vref(adc_unit_t adc_num,
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adc_atten_t atten,
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uint32_t vref,
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uint32_t *coeff_a,
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uint32_t *coeff_b)
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{
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const uint32_t *atten_scales;
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const uint32_t *atten_offsets;
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if (adc_num == ADC_UNIT_1) { //Using ADC 1
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atten_scales = adc1_vref_atten_scale;
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atten_offsets = adc1_vref_atten_offset;
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} else { //Using ADC 2
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atten_scales = adc2_vref_atten_scale;
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atten_offsets = adc2_vref_atten_offset;
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}
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//Characterize ADC-Voltage curve as y = (coeff_a * x) + coeff_b
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//Where coeff_a = (vref/4096) * atten_scale
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*coeff_a = (vref * atten_scales[atten]) / (ADC_12_BIT_RES);
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*coeff_b = atten_offsets[atten];
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}
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/* ------------------------ Conversion Functions --------------------------- */
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static uint32_t calculate_voltage_linear(uint32_t adc_reading, uint32_t coeff_a, uint32_t coeff_b)
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{
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//Where voltage = coeff_a * adc_reading + coeff_b
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return (((coeff_a * adc_reading) + LIN_COEFF_A_ROUND) / LIN_COEFF_A_SCALE) + coeff_b;
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}
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//Only call when ADC reading is above threshold
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static uint32_t calculate_voltage_lut(uint32_t adc, uint32_t vref, const uint32_t *low_vref_curve, const uint32_t *high_vref_curve)
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{
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//Get index of lower bound points of LUT
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uint32_t i = (adc - LUT_LOW_THRESH) / LUT_ADC_STEP_SIZE;
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//Let the X Axis be Vref, Y axis be ADC reading, and Z be voltage
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int x2dist = LUT_VREF_HIGH - vref; //(x2 - x)
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int x1dist = vref - LUT_VREF_LOW; //(x - x1)
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int y2dist = ((i + 1) * LUT_ADC_STEP_SIZE) + LUT_LOW_THRESH - adc; //(y2 - y)
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int y1dist = adc - ((i * LUT_ADC_STEP_SIZE) + LUT_LOW_THRESH); //(y - y1)
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//For points for bilinear interpolation
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int q11 = low_vref_curve[i]; //Lower bound point of low_vref_curve
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int q12 = low_vref_curve[i + 1]; //Upper bound point of low_vref_curve
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int q21 = high_vref_curve[i]; //Lower bound point of high_vref_curve
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int q22 = high_vref_curve[i + 1]; //Upper bound point of high_vref_curve
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//Bilinear interpolation
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//Where z = 1/((x2-x1)*(y2-y1)) * ( (q11*x2dist*y2dist) + (q21*x1dist*y2dist) + (q12*x2dist*y1dist) + (q22*x1dist*y1dist) )
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int voltage = (q11 * x2dist * y2dist) + (q21 * x1dist * y2dist) + (q12 * x2dist * y1dist) + (q22 * x1dist * y1dist);
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voltage += ((LUT_VREF_HIGH - LUT_VREF_LOW) * LUT_ADC_STEP_SIZE) / 2; //Integer division rounding
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voltage /= ((LUT_VREF_HIGH - LUT_VREF_LOW) * LUT_ADC_STEP_SIZE); //Divide by ((x2-x1)*(y2-y1))
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return (uint32_t)voltage;
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}
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static inline uint32_t interpolate_two_points(uint32_t y1, uint32_t y2, uint32_t x_step, uint32_t x)
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{
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//Interpolate between two points (x1,y1) (x2,y2) between 'lower' and 'upper' separated by 'step'
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return ((y1 * x_step) + (y2 * x) - (y1 * x) + (x_step / 2)) / x_step;
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}
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/* ------------------------- Public API ------------------------------------- */
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esp_err_t esp_adc_cal_check_efuse(esp_adc_cal_value_t source)
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{
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if (source == ESP_ADC_CAL_VAL_EFUSE_TP) {
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return (check_efuse_tp()) ? ESP_OK : ESP_ERR_NOT_SUPPORTED;
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} else if (source == ESP_ADC_CAL_VAL_EFUSE_VREF) {
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return (check_efuse_vref()) ? ESP_OK : ESP_ERR_NOT_SUPPORTED;
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} else {
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return ESP_ERR_INVALID_ARG;
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}
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}
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esp_adc_cal_value_t esp_adc_cal_characterize(adc_unit_t adc_num,
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adc_atten_t atten,
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adc_bits_width_t bit_width,
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uint32_t default_vref,
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esp_adc_cal_characteristics_t *chars)
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{
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//Check parameters
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assert((adc_num == ADC_UNIT_1) || (adc_num == ADC_UNIT_2));
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assert(chars != NULL);
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assert(bit_width < ADC_WIDTH_MAX);
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//Check eFuse if enabled to do so
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bool efuse_tp_present = check_efuse_tp();
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bool efuse_vref_present = check_efuse_vref();
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esp_adc_cal_value_t ret;
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if (efuse_tp_present && EFUSE_TP_ENABLED) {
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//Characterize based on Two Point values
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uint32_t high = read_efuse_tp_high(adc_num);
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uint32_t low = read_efuse_tp_low(adc_num);
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characterize_using_two_point(adc_num, atten, high, low, &chars->coeff_a, &chars->coeff_b);
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ret = ESP_ADC_CAL_VAL_EFUSE_TP;
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} else if (efuse_vref_present && EFUSE_VREF_ENABLED) {
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//Characterize based on eFuse Vref
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uint32_t vref = read_efuse_vref();
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characterize_using_vref(adc_num, atten, vref, &chars->coeff_a, &chars->coeff_b);
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ret = ESP_ADC_CAL_VAL_EFUSE_VREF;
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} else {
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//Characterized based on default Vref
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characterize_using_vref(adc_num, atten, default_vref, &chars->coeff_a, &chars->coeff_b);
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ret = ESP_ADC_CAL_VAL_DEFAULT_VREF;
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}
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//Initialized remaining fields
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chars->adc_num = adc_num;
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chars->atten = atten;
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chars->bit_width = bit_width;
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chars->vref = (EFUSE_VREF_ENABLED && efuse_vref_present) ? read_efuse_vref() : default_vref;
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//Initialize fields for lookup table if necessary
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if (LUT_ENABLED && atten == ADC_ATTEN_DB_11) {
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chars->low_curve = (adc_num == ADC_UNIT_1) ? lut_adc1_low : lut_adc2_low;
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chars->high_curve = (adc_num == ADC_UNIT_1) ? lut_adc1_high : lut_adc2_high;
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} else {
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chars->low_curve = NULL;
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chars->high_curve = NULL;
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}
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return ret;
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}
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uint32_t esp_adc_cal_raw_to_voltage(uint32_t adc_reading, const esp_adc_cal_characteristics_t *chars)
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{
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assert(chars != NULL);
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//Scale adc_rading if not 12 bits wide
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adc_reading = (adc_reading << (ADC_WIDTH_BIT_12 - chars->bit_width));
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if (adc_reading > ADC_12_BIT_RES - 1) {
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adc_reading = ADC_12_BIT_RES - 1; //Set to 12bit res max
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}
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if (LUT_ENABLED && (chars->atten == ADC_ATTEN_DB_11) && (adc_reading >= LUT_LOW_THRESH)) { //Check if in non-linear region
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//Use lookup table to get voltage in non linear portion of ADC_ATTEN_DB_11
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uint32_t lut_voltage = calculate_voltage_lut(adc_reading, chars->vref, chars->low_curve, chars->high_curve);
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if (adc_reading <= LUT_HIGH_THRESH) { //If ADC is transitioning from linear region to non-linear region
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//Linearly interpolate between linear voltage and lut voltage
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uint32_t linear_voltage = calculate_voltage_linear(adc_reading, chars->coeff_a, chars->coeff_b);
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return interpolate_two_points(linear_voltage, lut_voltage, LUT_ADC_STEP_SIZE, (adc_reading - LUT_LOW_THRESH));
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} else {
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return lut_voltage;
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}
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} else {
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return calculate_voltage_linear(adc_reading, chars->coeff_a, chars->coeff_b);
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}
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}
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