add board battery percentage

examples/companion_radio/UITask.cpp

@@ -143,11 +143,7 @@ void UITask::newMsg(uint8_t path_len, const char* from_name, const char* text, i
   }
 }
 
-void UITask::renderBatteryIndicator(uint16_t batteryMilliVolts) {
-  // Convert millivolts to percentage
-  const int minMilliVolts = 3000; // Minimum voltage (e.g., 3.0V)
-  const int maxMilliVolts = 4200; // Maximum voltage (e.g., 4.2V)
-  int batteryPercentage = ((batteryMilliVolts - minMilliVolts) * 100) / (maxMilliVolts - minMilliVolts);
+void UITask::renderBatteryIndicator(uint16_t batteryPercentage) {
   if (batteryPercentage < 0) batteryPercentage = 0; // Clamp to 0%
   if (batteryPercentage > 100) batteryPercentage = 100; // Clamp to 100%
 
@@ -222,7 +218,7 @@ void UITask::renderCurrScreen() {
     _display->print(_node_prefs->node_name);
 
     // battery voltage
-    renderBatteryIndicator(_board->getBattMilliVolts());
+    renderBatteryIndicator(_board->getBattPercent());
 
     // freq / sf
     _display->setCursor(0, 20);

examples/companion_radio/UITask.h

@@ -51,7 +51,7 @@ class UITask {
 
   void renderCurrScreen();
   void userLedHandler();
-  void renderBatteryIndicator(uint16_t batteryMilliVolts);
+  void renderBatteryIndicator(uint16_t batteryPercentage);
 
   // Button action handlers
   void handleButtonAnyPress();

src/MeshCore.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <stdint.h>
+#include "helpers/Battery.h"
 
 #define MAX_HASH_SIZE        8
 #define PUB_KEY_SIZE        32
@@ -36,6 +37,11 @@ namespace mesh {
 class MainBoard {
 public:
   virtual uint16_t getBattMilliVolts() = 0;
+  uint16_t getBattPercent() {
+    uint16_t mv = getBattMilliVolts();
+    return batt_percent(getBattType(), mv);
+  }
+  uint8_t getBattType() { return BATT_LIPO; };
   virtual const char* getManufacturerName() const = 0;
   virtual void onBeforeTransmit() { }
   virtual void onAfterTransmit() { }

src/helpers/Battery.cpp

@@ -0,0 +1,18 @@
+#include <Arduino.h>
+#include "Battery.h"
+
+uint16_t batt_percent(uint8_t batt, uint16_t mv) {
+    uint16_t last = mv; // set last to mv so it can never start greater than itself
+    uint16_t p = 0;
+    // 101 elements including 0 percentile
+    for (int i = 0; i < 101; i++) {
+        // if we match the current value or are between the current and last value
+        // we return the lower of the the two, giving accuracy +/- 1% soc
+        if (mv <= last && mv >= batt_curve[i][batt]) {
+            p = batt_curve[i][batt_p_col];
+            break;
+        }
+        last = batt_curve[i][batt];
+    } 
+    return p;
+};

src/helpers/Battery.h

@@ -0,0 +1,122 @@
+/*
+helpers/Battery.h defines battery chemistry types and their discharge curves
+*/
+
+// BATT_TYPE is a unique ID for battery chemistry type
+// NOTE: enum for curve must match index in table curve
+enum BATT_TYPE { BATT_LIPO, BATT_LIFEPO4 };
+
+uint16_t batt_percent(uint8_t batt, uint16_t mv);
+
+// batt_p_col is the column index of the battery percentage in the below table
+const int batt_p_col = 2;
+
+// batt_curve maps the battery voltage in mV to
+// the approximate SoC for a typical cell
+// Each column represents the mV for a given Soc foe that chemistry
+// COL1 = LIPO, COL2 = LIFEPO4, COL3 = percent charge
+// reference used https://blog.ampow.com/lipo-voltage-chart/
+// reference used https://cleversolarpower.com/lifepo4-voltage-chart/
+const uint16_t batt_curve[101][3] = {
+    { 4200, 3400, 100 },
+    { 4190, 3395, 99 },
+    { 4180, 3390, 98 },
+    { 4170, 3385, 97 },
+    { 4160, 3380, 96 },
+    { 4150, 3375, 95 },
+    { 4142, 3370, 94 },
+    { 4134, 3365, 93 },
+    { 4126, 3360, 92 },
+    { 4118, 3355, 91 },
+    { 4110, 3350, 90 },
+    { 4104, 3347, 89 },
+    { 4098, 3344, 88 },
+    { 4092, 3341, 87 },
+    { 4086, 3338, 86 },
+    { 4080, 3335, 85 },
+    { 4068, 3332, 84 },
+    { 4056, 3329, 83 },
+    { 4044, 3326, 82 },
+    { 4032, 3323, 81 },
+    { 4020, 3320, 80 },
+    { 4012, 3318, 79 },
+    { 4004, 3316, 78 },
+    { 3996, 3314, 77 },
+    { 3988, 3312, 76 },
+    { 3980, 3310, 75 },
+    { 3974, 3308, 74 },
+    { 3968, 3306, 73 },
+    { 3962, 3304, 72 },
+    { 3956, 3302, 71 },
+    { 3950, 3300, 70 },
+    { 3942, 3297, 69 },
+    { 3934, 3294, 68 },
+    { 3926, 3291, 67 },
+    { 3918, 3288, 66 },
+    { 3910, 3285, 65 },
+    { 3902, 3282, 64 },
+    { 3894, 3279, 63 },
+    { 3886, 3276, 62 },
+    { 3878, 3273, 61 },
+    { 3870, 3270, 60 },
+    { 3866, 3269, 59 },
+    { 3862, 3268, 58 },
+    { 3858, 3267, 57 },
+    { 3854, 3266, 56 },
+    { 3850, 3265, 55 },
+    { 3848, 3264, 54 },
+    { 3846, 3263, 53 },
+    { 3844, 3262, 52 },
+    { 3842, 3261, 51 },
+    { 3840, 3260, 50 },
+    { 3836, 3259, 49 },
+    { 3832, 3258, 48 },
+    { 3828, 3257, 47 },
+    { 3824, 3256, 46 },
+    { 3820, 3255, 45 },
+    { 3816, 3254, 44 },
+    { 3812, 3253, 43 },
+    { 3808, 3252, 42 },
+    { 3804, 3251, 41 },
+    { 3800, 3250, 40 },
+    { 3798, 3247, 39 },
+    { 3796, 3244, 38 },
+    { 3794, 3241, 37 },
+    { 3792, 3238, 36 },
+    { 3790, 3235, 35 },
+    { 3786, 3232, 34 },
+    { 3782, 3229, 33 },
+    { 3778, 3226, 32 },
+    { 3774, 3223, 31 },
+    { 3770, 3220, 30 },
+    { 3766, 3218, 29 },
+    { 3762, 3216, 28 },
+    { 3758, 3214, 27 },
+    { 3754, 3212, 26 },
+    { 3750, 3210, 25 },
+    { 3746, 3208, 24 },
+    { 3742, 3206, 23 },
+    { 3738, 3204, 22 },
+    { 3724, 3202, 21 },
+    { 3730, 3200, 20 },
+    { 3726, 3180, 19 },
+    { 3722, 3160, 18 },
+    { 3718, 3140, 17 },
+    { 3714, 3120, 16 },
+    { 3710, 3100, 15 },
+    { 3706, 3080, 14 },
+    { 3702, 3060, 13 },
+    { 3698, 3040, 12 },
+    { 3694, 3020, 11 },
+    { 3690, 3000, 10 },
+    { 3674, 2950, 9 },
+    { 3658, 2900, 8 },
+    { 3642, 2850, 7 },
+    { 3626, 2800, 6 },
+    { 3610, 2750, 5 },
+    { 3542, 2700, 4 },
+    { 3474, 2650, 3 },
+    { 3406, 2600, 2 },
+    { 3338, 2550, 1 },
+    { 3270, 2500, 0 }
+};