1 // Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
7 // http://www.apache.org/licenses/LICENSE-2.0
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
16 #include "esp_types.h"
17 #include "driver/adc.h"
18 #include "soc/efuse_reg.h"
21 #include "esp_adc_cal.h"
23 /* ----------------------------- Configuration ------------------------------ */
24 #ifdef CONFIG_ADC_CAL_EFUSE_TP_ENABLE
25 #define EFUSE_TP_ENABLED 1
27 #define EFUSE_TP_ENABLED 0
30 #ifdef CONFIG_ADC_CAL_EFUSE_VREF_ENABLE
31 #define EFUSE_VREF_ENABLED 1
33 #define EFUSE_VREF_ENABLED 0
36 #ifdef CONFIG_ADC_CAL_LUT_ENABLE
42 /* ESP32s with both Two Point Values and Vref burned into eFuse are required to
43 * also also burn the EFUSE_BLK3_PART_RESERVE flag. A limited set of ESP32s
44 * (not available through regular sales channel) DO NOT have the
45 * EFUSE_BLK3_PART_RESERVE burned. Moreover, this set of ESP32s represents Vref
46 * in Two's Complement format. If this is the case, modify the preprocessor
47 * definitions below as follows...
48 * #define CHECK_BLK3_FLAG 0 //Do not check BLK3 flag as it is not burned
49 * #define VREF_FORMAT 1 //eFuse Vref is in Two's Complement format
51 #define CHECK_BLK3_FLAG 1
54 /* ------------------------------ eFuse Access ----------------------------- */
55 #define BLK3_RESERVED_REG EFUSE_BLK0_RDATA3_REG
57 #define VREF_REG EFUSE_BLK0_RDATA4_REG
58 #define VREF_MASK 0x1F
59 #define VREF_STEP_SIZE 7
60 #define VREF_OFFSET 1100
62 #define TP_REG EFUSE_BLK3_RDATA3_REG
63 #define TP_LOW1_OFFSET 278
64 #define TP_LOW2_OFFSET 421
65 #define TP_LOW_MASK 0x7F
66 #define TP_LOW_VOLTAGE 150
67 #define TP_HIGH1_OFFSET 3265
68 #define TP_HIGH2_OFFSET 3406
69 #define TP_HIGH_MASK 0x1FF
70 #define TP_HIGH_VOLTAGE 850
71 #define TP_STEP_SIZE 4
73 /* ----------------------- Raw to Voltage Constants ------------------------- */
74 #define LIN_COEFF_A_SCALE 65536
75 #define LIN_COEFF_A_ROUND (LIN_COEFF_A_SCALE/2)
77 #define LUT_VREF_LOW 1000
78 #define LUT_VREF_HIGH 1200
79 #define LUT_ADC_STEP_SIZE 64
81 #define LUT_LOW_THRESH 2880
82 #define LUT_HIGH_THRESH (LUT_LOW_THRESH + LUT_ADC_STEP_SIZE)
83 #define ADC_12_BIT_RES 4096
85 #define ADC_CAL_CHECK(cond, ret) ({ \
91 /* ------------------------ Characterization Constants ---------------------- */
92 static const uint32_t adc1_tp_atten_scale[4] = {65504, 86975, 120389, 224310};
93 static const uint32_t adc2_tp_atten_scale[4] = {65467, 86861, 120416, 224708};
94 static const uint32_t adc1_tp_atten_offset[4] = {0, 1, 27, 54};
95 static const uint32_t adc2_tp_atten_offset[4] = {0, 9, 26, 66};
97 static const uint32_t adc1_vref_atten_scale[4] = {57431, 76236, 105481, 196602};
98 static const uint32_t adc2_vref_atten_scale[4] = {57236, 76175, 105678, 197170};
99 static const uint32_t adc1_vref_atten_offset[4] = {75, 78, 107, 142};
100 static const uint32_t adc2_vref_atten_offset[4] = {63, 66, 89, 128};
102 //20 Point lookup tables, covering ADC readings from 2880 to 4096, step size of 64
103 static const uint32_t lut_adc1_low[LUT_POINTS] = {2240, 2297, 2352, 2405, 2457, 2512, 2564, 2616, 2664, 2709,
104 2754, 2795, 2832, 2868, 2903, 2937, 2969, 3000, 3030, 3060};
105 static const uint32_t lut_adc1_high[LUT_POINTS] = {2667, 2706, 2745, 2780, 2813, 2844, 2873, 2901, 2928, 2956,
106 2982, 3006, 3032, 3059, 3084, 3110, 3135, 3160, 3184, 3209};
107 static const uint32_t lut_adc2_low[LUT_POINTS] = {2238, 2293, 2347, 2399, 2451, 2507, 2561, 2613, 2662, 2710,
108 2754, 2792, 2831, 2869, 2904, 2937, 2968, 2999, 3029, 3059};
109 static const uint32_t lut_adc2_high[LUT_POINTS] = {2657, 2698, 2738, 2774, 2807, 2838, 2867, 2894, 2921, 2946,
110 2971, 2996, 3020, 3043, 3067, 3092, 3116, 3139, 3162, 3185};
112 /* ----------------------- EFuse Access Functions --------------------------- */
113 static bool check_efuse_vref()
115 //Check if Vref is burned in eFuse
116 return (REG_GET_FIELD(VREF_REG, EFUSE_RD_ADC_VREF) != 0) ? true : false;
119 static bool check_efuse_tp()
121 //Check if Two Point values are burned in eFuse
122 if (CHECK_BLK3_FLAG && (REG_GET_FIELD(BLK3_RESERVED_REG, EFUSE_RD_BLK3_PART_RESERVE) == 0)) {
125 //All TP cal values must be non zero
126 if ((REG_GET_FIELD(TP_REG, EFUSE_RD_ADC1_TP_LOW) != 0) &&
127 (REG_GET_FIELD(TP_REG, EFUSE_RD_ADC2_TP_LOW) != 0) &&
128 (REG_GET_FIELD(TP_REG, EFUSE_RD_ADC1_TP_HIGH) != 0) &&
129 (REG_GET_FIELD(TP_REG, EFUSE_RD_ADC2_TP_HIGH) != 0)) {
136 static inline int decode_bits(uint32_t bits, uint32_t mask, bool is_twos_compl)
139 if (bits & (~(mask >> 1) & mask)) { //Check sign bit (MSB of mask)
142 ret = -(((~bits) + 1) & (mask >> 1)); //2's complement
144 ret = -(bits & (mask >> 1)); //Sign-magnitude
148 ret = bits & (mask >> 1);
153 static uint32_t read_efuse_vref()
155 //eFuse stores deviation from ideal reference voltage
156 uint32_t ret = VREF_OFFSET; //Ideal vref
157 uint32_t bits = REG_GET_FIELD(VREF_REG, EFUSE_ADC_VREF);
158 ret += decode_bits(bits, VREF_MASK, VREF_FORMAT) * VREF_STEP_SIZE;
159 return ret; //ADC Vref in mV
162 static uint32_t read_efuse_tp_low(adc_unit_t adc_num)
164 //ADC reading at 150mV stored in two's complement format
168 if (adc_num == ADC_UNIT_1) {
169 ret = TP_LOW1_OFFSET;
170 bits = REG_GET_FIELD(TP_REG, EFUSE_RD_ADC1_TP_LOW);
172 ret = TP_LOW2_OFFSET;
173 bits = REG_GET_FIELD(TP_REG, EFUSE_RD_ADC2_TP_LOW);
175 ret += decode_bits(bits, TP_LOW_MASK, true) * TP_STEP_SIZE;
176 return ret; //Reading of ADC at 150mV
179 static uint32_t read_efuse_tp_high(adc_unit_t adc_num)
181 //ADC reading at 850mV stored in two's complement format
185 if (adc_num == ADC_UNIT_1) {
186 ret = TP_HIGH1_OFFSET;
187 bits = REG_GET_FIELD(TP_REG, EFUSE_RD_ADC1_TP_HIGH);
189 ret = TP_HIGH2_OFFSET;
190 bits = REG_GET_FIELD(TP_REG, EFUSE_RD_ADC2_TP_HIGH);
192 ret += decode_bits(bits, TP_HIGH_MASK, true) * TP_STEP_SIZE;
193 return ret; //Reading of ADC at 850mV
196 /* ----------------------- Characterization Functions ----------------------- */
197 static void characterize_using_two_point(adc_unit_t adc_num,
204 const uint32_t *atten_scales;
205 const uint32_t *atten_offsets;
207 if (adc_num == ADC_UNIT_1) { //Using ADC 1
208 atten_scales = adc1_tp_atten_scale;
209 atten_offsets = adc1_tp_atten_offset;
210 } else { //Using ADC 2
211 atten_scales = adc2_tp_atten_scale;
212 atten_offsets = adc2_tp_atten_offset;
214 //Characterize ADC-Voltage curve as y = (coeff_a * x) + coeff_b
215 uint32_t delta_x = high - low;
216 uint32_t delta_v = TP_HIGH_VOLTAGE - TP_LOW_VOLTAGE;
217 //Where coeff_a = (delta_v/delta_x) * atten_scale
218 *coeff_a = (delta_v * atten_scales[atten] + (delta_x / 2)) / delta_x; //+(delta_x/2) for rounding
219 //Where coeff_b = high_v - ((delta_v/delta_x) * high_x) + atten_offset
220 *coeff_b = TP_HIGH_VOLTAGE - ((delta_v * high + (delta_x / 2)) / delta_x) + atten_offsets[atten];
223 static void characterize_using_vref(adc_unit_t adc_num,
229 const uint32_t *atten_scales;
230 const uint32_t *atten_offsets;
232 if (adc_num == ADC_UNIT_1) { //Using ADC 1
233 atten_scales = adc1_vref_atten_scale;
234 atten_offsets = adc1_vref_atten_offset;
235 } else { //Using ADC 2
236 atten_scales = adc2_vref_atten_scale;
237 atten_offsets = adc2_vref_atten_offset;
239 //Characterize ADC-Voltage curve as y = (coeff_a * x) + coeff_b
240 //Where coeff_a = (vref/4096) * atten_scale
241 *coeff_a = (vref * atten_scales[atten]) / (ADC_12_BIT_RES);
242 *coeff_b = atten_offsets[atten];
245 /* ------------------------ Conversion Functions --------------------------- */
246 static uint32_t calculate_voltage_linear(uint32_t adc_reading, uint32_t coeff_a, uint32_t coeff_b)
248 //Where voltage = coeff_a * adc_reading + coeff_b
249 return (((coeff_a * adc_reading) + LIN_COEFF_A_ROUND) / LIN_COEFF_A_SCALE) + coeff_b;
252 //Only call when ADC reading is above threshold
253 static uint32_t calculate_voltage_lut(uint32_t adc, uint32_t vref, const uint32_t *low_vref_curve, const uint32_t *high_vref_curve)
255 //Get index of lower bound points of LUT
256 uint32_t i = (adc - LUT_LOW_THRESH) / LUT_ADC_STEP_SIZE;
258 //Let the X Axis be Vref, Y axis be ADC reading, and Z be voltage
259 int x2dist = LUT_VREF_HIGH - vref; //(x2 - x)
260 int x1dist = vref - LUT_VREF_LOW; //(x - x1)
261 int y2dist = ((i + 1) * LUT_ADC_STEP_SIZE) + LUT_LOW_THRESH - adc; //(y2 - y)
262 int y1dist = adc - ((i * LUT_ADC_STEP_SIZE) + LUT_LOW_THRESH); //(y - y1)
264 //For points for bilinear interpolation
265 int q11 = low_vref_curve[i]; //Lower bound point of low_vref_curve
266 int q12 = low_vref_curve[i + 1]; //Upper bound point of low_vref_curve
267 int q21 = high_vref_curve[i]; //Lower bound point of high_vref_curve
268 int q22 = high_vref_curve[i + 1]; //Upper bound point of high_vref_curve
270 //Bilinear interpolation
271 //Where z = 1/((x2-x1)*(y2-y1)) * ( (q11*x2dist*y2dist) + (q21*x1dist*y2dist) + (q12*x2dist*y1dist) + (q22*x1dist*y1dist) )
272 int voltage = (q11 * x2dist * y2dist) + (q21 * x1dist * y2dist) + (q12 * x2dist * y1dist) + (q22 * x1dist * y1dist);
273 voltage += ((LUT_VREF_HIGH - LUT_VREF_LOW) * LUT_ADC_STEP_SIZE) / 2; //Integer division rounding
274 voltage /= ((LUT_VREF_HIGH - LUT_VREF_LOW) * LUT_ADC_STEP_SIZE); //Divide by ((x2-x1)*(y2-y1))
275 return (uint32_t)voltage;
278 static inline uint32_t interpolate_two_points(uint32_t y1, uint32_t y2, uint32_t x_step, uint32_t x)
280 //Interpolate between two points (x1,y1) (x2,y2) between 'lower' and 'upper' separated by 'step'
281 return ((y1 * x_step) + (y2 * x) - (y1 * x) + (x_step / 2)) / x_step;
284 /* ------------------------- Public API ------------------------------------- */
285 esp_err_t esp_adc_cal_check_efuse(esp_adc_cal_value_t source)
287 if (source == ESP_ADC_CAL_VAL_EFUSE_TP) {
288 return (check_efuse_tp()) ? ESP_OK : ESP_ERR_NOT_SUPPORTED;
289 } else if (source == ESP_ADC_CAL_VAL_EFUSE_VREF) {
290 return (check_efuse_vref()) ? ESP_OK : ESP_ERR_NOT_SUPPORTED;
292 return ESP_ERR_INVALID_ARG;
296 esp_adc_cal_value_t esp_adc_cal_characterize(adc_unit_t adc_num,
298 adc_bits_width_t bit_width,
299 uint32_t default_vref,
300 esp_adc_cal_characteristics_t *chars)
303 assert((adc_num == ADC_UNIT_1) || (adc_num == ADC_UNIT_2));
304 assert(chars != NULL);
305 assert(bit_width < ADC_WIDTH_MAX);
307 //Check eFuse if enabled to do so
308 bool efuse_tp_present = check_efuse_tp();
309 bool efuse_vref_present = check_efuse_vref();
310 esp_adc_cal_value_t ret;
312 if (efuse_tp_present && EFUSE_TP_ENABLED) {
313 //Characterize based on Two Point values
314 uint32_t high = read_efuse_tp_high(adc_num);
315 uint32_t low = read_efuse_tp_low(adc_num);
316 characterize_using_two_point(adc_num, atten, high, low, &chars->coeff_a, &chars->coeff_b);
317 ret = ESP_ADC_CAL_VAL_EFUSE_TP;
318 } else if (efuse_vref_present && EFUSE_VREF_ENABLED) {
319 //Characterize based on eFuse Vref
320 uint32_t vref = read_efuse_vref();
321 characterize_using_vref(adc_num, atten, vref, &chars->coeff_a, &chars->coeff_b);
322 ret = ESP_ADC_CAL_VAL_EFUSE_VREF;
324 //Characterized based on default Vref
325 characterize_using_vref(adc_num, atten, default_vref, &chars->coeff_a, &chars->coeff_b);
326 ret = ESP_ADC_CAL_VAL_DEFAULT_VREF;
329 //Initialized remaining fields
330 chars->adc_num = adc_num;
331 chars->atten = atten;
332 chars->bit_width = bit_width;
333 chars->vref = (EFUSE_VREF_ENABLED && efuse_vref_present) ? read_efuse_vref() : default_vref;
334 //Initialize fields for lookup table if necessary
335 if (LUT_ENABLED && atten == ADC_ATTEN_DB_11) {
336 chars->low_curve = (adc_num == ADC_UNIT_1) ? lut_adc1_low : lut_adc2_low;
337 chars->high_curve = (adc_num == ADC_UNIT_1) ? lut_adc1_high : lut_adc2_high;
339 chars->low_curve = NULL;
340 chars->high_curve = NULL;
345 uint32_t esp_adc_cal_raw_to_voltage(uint32_t adc_reading, const esp_adc_cal_characteristics_t *chars)
347 assert(chars != NULL);
349 //Scale adc_rading if not 12 bits wide
350 adc_reading = (adc_reading << (ADC_WIDTH_BIT_12 - chars->bit_width));
351 if (adc_reading > ADC_12_BIT_RES - 1) {
352 adc_reading = ADC_12_BIT_RES - 1; //Set to 12bit res max
355 if (LUT_ENABLED && (chars->atten == ADC_ATTEN_DB_11) && (adc_reading >= LUT_LOW_THRESH)) { //Check if in non-linear region
356 //Use lookup table to get voltage in non linear portion of ADC_ATTEN_DB_11
357 uint32_t lut_voltage = calculate_voltage_lut(adc_reading, chars->vref, chars->low_curve, chars->high_curve);
358 if (adc_reading <= LUT_HIGH_THRESH) { //If ADC is transitioning from linear region to non-linear region
359 //Linearly interpolate between linear voltage and lut voltage
360 uint32_t linear_voltage = calculate_voltage_linear(adc_reading, chars->coeff_a, chars->coeff_b);
361 return interpolate_two_points(linear_voltage, lut_voltage, LUT_ADC_STEP_SIZE, (adc_reading - LUT_LOW_THRESH));
366 return calculate_voltage_linear(adc_reading, chars->coeff_a, chars->coeff_b);
370 esp_err_t esp_adc_cal_get_voltage(adc_channel_t channel,
371 const esp_adc_cal_characteristics_t *chars,
375 ADC_CAL_CHECK(chars != NULL, ESP_ERR_INVALID_ARG);
376 ADC_CAL_CHECK(voltage != NULL, ESP_ERR_INVALID_ARG);
379 if (chars->adc_num == ADC_UNIT_1) {
380 //Check channel is valid on ADC1
381 ADC_CAL_CHECK((adc1_channel_t)channel < ADC1_CHANNEL_MAX, ESP_ERR_INVALID_ARG);
382 adc_reading = adc1_get_raw(channel);
384 //Check channel is valid on ADC2
385 ADC_CAL_CHECK((adc2_channel_t)channel < ADC2_CHANNEL_MAX, ESP_ERR_INVALID_ARG);
386 if (adc2_get_raw(channel, chars->bit_width, &adc_reading) != ESP_OK) {
387 return ESP_ERR_TIMEOUT; //Timed out waiting for ADC2
390 *voltage = esp_adc_cal_raw_to_voltage((uint32_t)adc_reading, chars);
394 /* ------------------------ Deprecated API --------------------------------- */
395 void esp_adc_cal_get_characteristics(uint32_t vref,
397 adc_bits_width_t bit_width,
398 esp_adc_cal_characteristics_t *chars)
400 assert(chars != NULL);
401 esp_adc_cal_characterize(ADC_UNIT_1, atten, bit_width, vref, chars);
404 uint32_t adc1_to_voltage(adc1_channel_t channel, const esp_adc_cal_characteristics_t *chars)
406 assert(chars != NULL);
407 uint32_t voltage = 0;
408 esp_adc_cal_get_voltage((adc_channel_t)channel, chars, &voltage);