Merge pull request #208 from Professr/issue#196

Added battery charge percentage support, Issue#196

src/esp32/main-esp32.cpp

@@ -75,6 +75,16 @@ void readPowerStatus()
     powerStatus.haveBattery = axp.isBatteryConnect();
     if (powerStatus.haveBattery) {
         powerStatus.batteryVoltageMv = axp.getBattVoltage();
+        // If the AXP192 returns a valid battery percentage, use it
+        if (axp.getBattPercentage() >= 0) {
+            powerStatus.batteryChargePercent = axp.getBattPercentage();
+        } 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
+            int calculatedPercentage = ((powerStatus.batteryVoltageMv - BAT_MILLIVOLTS_EMPTY) * 1e2) / (BAT_MILLIVOLTS_FULL - BAT_MILLIVOLTS_EMPTY);
+            powerStatus.batteryChargePercent = (calculatedPercentage < 0) ? 0 : (calculatedPercentage > 100) ? 100 : calculatedPercentage;
+        }
+        DEBUG_MSG("Battery %dmV %d%%\n", powerStatus.batteryVoltageMv, powerStatus.batteryChargePercent);
     }
     powerStatus.usb = axp.isVBUSPlug();
     powerStatus.charging = axp.isChargeing();
@@ -205,15 +215,6 @@ uint32_t axpDebugRead()
 Periodic axpDebugOutput(axpDebugRead);
 #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/
 
 /// loop code specific to ESP32 targets
 void esp32Loop()

src/power.h

@@ -1,5 +1,18 @@
 #pragma once
 
+/**
+ * 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
+
 namespace meshtastic
 {
 
@@ -9,6 +22,8 @@ struct PowerStatus {
     bool haveBattery;
     /// Battery voltage in mV, valid if haveBattery is true
     int batteryVoltageMv;
+    /// Battery charge percentage, either read directly or estimated
+    int batteryChargePercent;
     /// Whether USB is connected
     bool usb;
     /// Whether we are charging the battery

src/screen.cpp

@@ -658,9 +658,11 @@ void DebugInfo::drawFrame(OLEDDisplay *display, OLEDDisplayUiState *state, int16
         snprintf(channelStr, sizeof(channelStr), "%s", channelName.c_str());
         if (powerStatus.haveBattery) {
             // TODO: draw a battery icon instead of letter "B".
-            int batV = powerStatus.batteryVoltageMv / 1000;
-            int batCv = (powerStatus.batteryVoltageMv % 1000) / 10;
-            snprintf(batStr, sizeof(batStr), "B %01d.%02dV%c%c", batV, batCv, powerStatus.charging ? '+' : ' ',
+            //int batV = powerStatus.batteryVoltageMv / 1000;
+            //int batCv = (powerStatus.batteryVoltageMv % 1000) / 10;
+            //snprintf(batStr, sizeof(batStr), "B %01d.%02dV%c%c", batV, batCv, powerStatus.charging ? '+' : ' ',
+            //         powerStatus.usb ? 'U' : ' ');
+            snprintf(batStr, sizeof(batStr), "B %d%%%c%c", powerStatus.batteryChargePercent, powerStatus.charging ? '+' : ' ',
                      powerStatus.usb ? 'U' : ' ');
         } else {
             snprintf(batStr, sizeof(batStr), "%s", powerStatus.usb ? "USB" : "");