Battery level with proportional filter and lookup table

src/Power.cpp

@@ -127,8 +127,6 @@ class AnalogBatteryLevel : public HasBatteryLevel
 {
     /**
      * Battery state of charge, from 0 to 100 or -1 for unknown
-     *
-     * FIXME - use a lipo lookup table, the current % full is super wrong
      */
     virtual int getBatteryPercent() override
     {
@@ -137,13 +135,32 @@ class AnalogBatteryLevel : public HasBatteryLevel
         if (v < noBatVolt)
             return -1; // If voltage is super low assume no battery installed
 
-#ifdef ARCH_ESP32
+#ifdef NO_BATTERY_LEVEL_ON_CHARGE
         // This does not work on a RAK4631 with battery connected
         if (v > chargingVolt)
             return 0; // While charging we can't report % full on the battery
 #endif
-
-        return clamp((int)(100 * (v - emptyVolt) / (fullVolt - emptyVolt)), 0, 100);
+        /**
+         * @brief   Battery voltage lookup table interpolation to obtain a more
+         * precise percentage rather than the old proportional one.
+         * @author  Gabriele Russo
+         * @date    06/02/2024
+         */
+        float battery_SOC = 0.0;
+        uint16_t voltage = v / NUM_CELLS; // single cell voltage (average)
+        for (int i = 0; i < NUM_OCV_POINTS; i++) {
+            if (OCV[i] <= voltage) {
+                if (i == 0) {
+                    battery_SOC = 100.0; // 100% full
+                } else {
+                    // interpolate between OCV[i] and OCV[i-1]
+                    battery_SOC = (float)100.0 / (NUM_OCV_POINTS - 1.0) *
+                                  (NUM_OCV_POINTS - 1.0 - i + ((float)voltage - OCV[i]) / (OCV[i - 1] - OCV[i]));
+                }
+                break;
+            }
+        }
+        return clamp((int)(battery_SOC), 0, 100);
     }
 
     /**
@@ -165,7 +182,7 @@ class AnalogBatteryLevel : public HasBatteryLevel
 
 #ifndef BATTERY_SENSE_SAMPLES
 #define BATTERY_SENSE_SAMPLES                                                                                                    \
-    30 // Set the number of samples, it has an effect of increasing sensitivity in complex electromagnetic environment.
+    15 // Set the number of samples, it has an effect of increasing sensitivity in complex electromagnetic environment.
 #endif
 
 #ifdef BATTERY_PIN
@@ -191,12 +208,10 @@ class AnalogBatteryLevel : public HasBatteryLevel
             raw = raw / BATTERY_SENSE_SAMPLES;
             scaled = operativeAdcMultiplier * ((1000 * AREF_VOLTAGE) / pow(2, BATTERY_SENSE_RESOLUTION_BITS)) * raw;
 #endif
-            // LOG_DEBUG("battery gpio %d raw val=%u scaled=%u\n", BATTERY_PIN, raw, (uint32_t)(scaled));
-            last_read_value = scaled;
-            return scaled;
-        } else {
-            return last_read_value;
+            last_read_value += (scaled - last_read_value) * 0.5; // Virtual LPF
+            //LOG_DEBUG("battery gpio %d raw val=%u scaled=%u filtered=%u\n", BATTERY_PIN, raw, (uint32_t)(scaled), (uint32_t) (last_read_value));
         }
+        return last_read_value;
 #endif // BATTERY_PIN
         return 0;
     }
@@ -209,22 +224,24 @@ class AnalogBatteryLevel : public HasBatteryLevel
     {
 
         uint32_t raw = 0;
+        uint8_t raw_c = 0; //raw reading counter
 
 #ifndef BAT_MEASURE_ADC_UNIT // ADC1
-#ifdef ADC_CTRL
-        if (heltec_version == 5) {
-            pinMode(ADC_CTRL, OUTPUT);
-            digitalWrite(ADC_CTRL, HIGH);
-            delay(10);
-        }
+#ifdef ADC_CTRL //enable adc voltage divider when we need to read
+        pinMode(ADC_CTRL, OUTPUT);
+        digitalWrite(ADC_CTRL, ADC_CTRL_ENABLED);
+        delay(10);
 #endif
         for (int i = 0; i < BATTERY_SENSE_SAMPLES; i++) {
-            raw += adc1_get_raw(adc_channel);
-        }
-#ifdef ADC_CTRL
-        if (heltec_version == 5) {
-            digitalWrite(ADC_CTRL, LOW);
+            int val_ = adc1_get_raw(adc_channel);
+            if(val_ >= 0){ //save only valid readings
+                raw += val_;
+                raw_c ++;
+            }
+            // delayMicroseconds(100);
         }
+#ifdef ADC_CTRL //disable adc voltage divider when we need to read
+        digitalWrite(ADC_CTRL, !ADC_CTRL_ENABLED);
 #endif
 #else  // ADC2
         int32_t adc_buf = 0;
@@ -235,10 +252,10 @@ class AnalogBatteryLevel : public HasBatteryLevel
             SET_PERI_REG_MASK(SENS_SAR_READ_CTRL2_REG, SENS_SAR2_DATA_INV);
             adc2_get_raw(adc_channel, ADC_WIDTH_BIT_12, &adc_buf);
             raw += adc_buf;
+            raw_c ++;
         }
 #endif // BAT_MEASURE_ADC_UNIT
-        raw = raw / BATTERY_SENSE_SAMPLES;
-        return raw;
+        return (raw / (raw_c < 1 ? 1 : raw_c));
     }
 #endif
 
@@ -272,22 +289,14 @@ class AnalogBatteryLevel : public HasBatteryLevel
     /// If we see a battery voltage higher than physics allows - assume charger is pumping
     /// in power
 
-#ifndef BAT_FULLVOLT
-#define BAT_FULLVOLT 4200
-#endif
-#ifndef BAT_EMPTYVOLT
-#define BAT_EMPTYVOLT 3270
-#endif
-#ifndef BAT_CHARGINGVOLT
-#define BAT_CHARGINGVOLT 4210
-#endif
-#ifndef BAT_NOBATVOLT
-#define BAT_NOBATVOLT 2230
-#endif
-
-    /// For heltecs with no battery connected, the measured voltage is 2204, so raising to 2230 from 2100
-    const float fullVolt = BAT_FULLVOLT, emptyVolt = BAT_EMPTYVOLT, chargingVolt = BAT_CHARGINGVOLT, noBatVolt = BAT_NOBATVOLT;
-    float last_read_value = 0.0;
+    /// For heltecs with no battery connected, the measured voltage is 2204, so
+    // need to be higher than that, in this case is 2500mV (3000-500)
+    const uint16_t OCV[NUM_OCV_POINTS] = {OCV_ARRAY};
+    const float chargingVolt = (OCV[0] + 10) * NUM_CELLS;
+    const float noBatVolt = (OCV[NUM_OCV_POINTS - 1] - 500) * NUM_CELLS;
+    // Start value from minimum voltage for the filter to not start from 0
+    // that could trigger some events.
+    float last_read_value = (OCV[NUM_OCV_POINTS - 1] * NUM_CELLS);
     uint32_t last_read_time_ms = 0;
 
 #if defined(HAS_TELEMETRY) && !defined(ARCH_PORTDUINO)
@@ -377,10 +386,6 @@ bool Power::analogInit()
     } else {
         LOG_INFO("ADCmod: ADC characterization based on default reference voltage\n");
     }
-#if defined(HELTEC_V3) || defined(HELTEC_WSL_V3)
-    pinMode(37, OUTPUT); // needed for P channel mosfet to work
-    digitalWrite(37, LOW);
-#endif
 #endif // ARCH_ESP32
 
 #ifdef ARCH_NRF52
@@ -461,11 +466,11 @@ void Power::readPowerStatus()
                 batteryChargePercent = batteryLevel->getBatteryPercent();
             } else {
                 // If the AXP192 returns a percentage less than 0, the feature is either not supported or there is an error
-                // In that case, we compute an estimate of the charge percent based on maximum and minimum voltages defined in
-                // power.h
-                batteryChargePercent =
-                    clamp((int)(((batteryVoltageMv - BAT_MILLIVOLTS_EMPTY) * 1e2) / (BAT_MILLIVOLTS_FULL - BAT_MILLIVOLTS_EMPTY)),
-                          0, 100);
+                // In that case, we compute an estimate of the charge percent based on open circuite voltage table defined
+                // in power.h
+                batteryChargePercent = clamp((int)(((batteryVoltageMv - (OCV[NUM_OCV_POINTS - 1] * NUM_CELLS)) * 1e2) /
+                                                   ((OCV[0] * NUM_CELLS) - (OCV[NUM_OCV_POINTS - 1] * NUM_CELLS))),
+                                             0, 100);
             }
         }
 
@@ -530,10 +535,11 @@ void Power::readPowerStatus()
 
 #endif
 
-        // If we have a battery at all and it is less than 10% full, force deep sleep if we have more than 10 low readings in
-        // a row
+        // If we have a battery at all and it is less than 0%, force deep sleep if we have more than 10 low readings in
+        // a row. NOTE: min LiIon/LiPo voltage is 2.0 to 2.5V, current OCV min is set to 3100 that is large enough.
+        //
         if (powerStatus2.getHasBattery() && !powerStatus2.getHasUSB()) {
-            if (batteryLevel->getBattVoltage() < MIN_BAT_MILLIVOLTS) {
+            if (batteryLevel->getBattVoltage() < OCV[NUM_OCV_POINTS - 1]) {
                 low_voltage_counter++;
                 LOG_DEBUG("Low voltage counter: %d/10\n", low_voltage_counter);
                 if (low_voltage_counter > 10) {

src/power.h

@@ -5,18 +5,31 @@
 #include <esp_adc_cal.h>
 #include <soc/adc_channel.h>
 #endif
-/**
- * Per @spattinson
- * MIN_BAT_MILLIVOLTS seems high. Typical 18650 are different chemistry to LiPo, even for LiPos that chart seems a bit off, other
- * charts put 3690mV at about 30% for a lipo, for 18650 i think 10% remaining iis in the region of 3.2-3.3V. Reference 1st graph
- * in [this test report](https://lygte-info.dk/review/batteries2012/Samsung%20INR18650-30Q%203000mAh%20%28Pink%29%20UK.html)
- * looking at the red line - discharge at 0.2A - he gets a capacity of 2900mah, 90% of 2900 = 2610, that point in the graph looks
- * to be a shade above 3.2V
- */
-#define MIN_BAT_MILLIVOLTS 3250 // millivolts. 10% per https://blog.ampow.com/lipo-voltage-chart/
-
-#define BAT_MILLIVOLTS_FULL 4100
-#define BAT_MILLIVOLTS_EMPTY 3500
+
+#ifndef NUM_OCV_POINTS
+#define NUM_OCV_POINTS 11
+#endif
+
+// 3400,3350,3320,3290,3270,3260,3250,3230,3200,3120,3000 //3.4 to 3.0 LiFePO4
+// 2120,2090,2070,2050,2030,2010,1990,1980,1970,1960,1950 //2.12 to 1.95 Lead Acid
+// 4200,4050,3990,3890,3790,3700,3650,3550,3450,3300,3200 //4.2 to 3.2 LiIon/LiPo
+// 4200,4050,3990,3890,3790,3700,3650,3550,3400,3300,3000 //4.2 to 3.0 LiIon/LiPo
+// 4150,4050,3990,3890,3790,3690,3620,3520,3420,3300,3100 //4.15 to 3.1 LiIon/LiPo
+#ifndef OCV_ARRAY
+#ifdef CELL_TYPE_LIFEPO4
+#define OCV_ARRAY 3400, 3350, 3320, 3290, 3270, 3260, 3250, 3230, 3200, 3120, 3000
+#elif defined(CELL_TYPE_LEADACID)
+#define OCV_ARRAY 2120, 2090, 2070, 2050, 2030, 2010, 1990, 1980, 1970, 1960, 1950
+#else // LiIon
+#define OCV_ARRAY 4190, 4050, 3990, 3890, 3800, 3720, 3630, 3530, 3420, 3300, 3100
+#endif
+#endif
+
+/*Note: 12V lead acid is 6 cells, most board accept only 1 cell LiIon/LiPo*/
+#ifndef NUM_CELLS
+#define NUM_CELLS 1
+#endif
+
 #ifdef BAT_MEASURE_ADC_UNIT
 extern RTC_NOINIT_ATTR uint64_t RTC_reg_b;
 #include "soc/sens_reg.h" // needed for adc pin reset
@@ -44,6 +57,7 @@ class Power : private concurrency::OSThread
     virtual bool setup();
     virtual int32_t runOnce() override;
     void setStatusHandler(meshtastic::PowerStatus *handler) { statusHandler = handler; }
+    const uint16_t OCV[11] = {OCV_ARRAY};
 
   protected:
     meshtastic::PowerStatus *statusHandler;
@@ -54,6 +68,7 @@ class Power : private concurrency::OSThread
     bool analogInit();
 
   private:
+    // open circuit voltage lookup table
     uint8_t low_voltage_counter;
 #ifdef DEBUG_HEAP
     uint32_t lastheap;

variants/heltec_v2.1/variant.h

@@ -29,7 +29,8 @@
 #define LORA_DIO1 35 // https://www.thethingsnetwork.org/forum/t/big-esp32-sx127x-topic-part-3/18436
 #define LORA_DIO2 34 // Not really used
 
-#define ADC_MULTIPLIER 3.8
+#define ADC_MULTIPLIER 3.2 //220k + 100k (320k/100k=3.2)
+//#define ADC_WIDTH ADC_WIDTH_BIT_10
 
 #define BATTERY_PIN 37 // A battery voltage measurement pin, voltage divider connected here to measure battery voltage
 #define ADC_CHANNEL ADC1_GPIO37_CHANNEL

variants/heltec_v3/variant.h

@@ -11,6 +11,8 @@
 #define VEXT_ENABLE Vext // active low, powers the oled display and the lora antenna boost
 #define BUTTON_PIN 0
 
+#define ADC_CTRL 37
+#define ADC_CTRL_ENABLED LOW
 #define BATTERY_PIN 1 // A battery voltage measurement pin, voltage divider connected here to measure battery voltage
 #define ADC_CHANNEL ADC1_GPIO1_CHANNEL
 #define ADC_ATTENUATION ADC_ATTEN_DB_2_5 // lower dB for high resistance voltage divider

variants/heltec_wireless_tracker/variant.h

@@ -35,6 +35,7 @@
 #define ADC_ATTENUATION ADC_ATTEN_DB_2_5 // lower dB for high resistance voltage divider
 #define ADC_MULTIPLIER 4.9
 #define ADC_CTRL 2 // active HIGH, powers the voltage divider. Only on 1.1
+#define ADC_CTRL_ENABLED HIGH
 
 #undef GPS_RX_PIN
 #undef GPS_TX_PIN

variants/heltec_wsl_v3/variant.h

@@ -8,6 +8,8 @@
 #define VEXT_ENABLE Vext // active low, powers the oled display and the lora antenna boost
 #define BUTTON_PIN 0
 
+#define ADC_CTRL 37
+#define ADC_CTRL_ENABLED LOW
 #define BATTERY_PIN 1 // A battery voltage measurement pin, voltage divider connected here to measure battery voltage
 #define ADC_CHANNEL ADC1_GPIO1_CHANNEL
 #define ADC_ATTENUATION ADC_ATTEN_DB_2_5 // lower dB for high resistance voltage divider