From 6b86aa707ba59a179ab8500847a101d176e7f29e Mon Sep 17 00:00:00 2001
From: Stefan Brand <seiichiro@seiichiro0185.org>
Date: Mon, 24 May 2021 16:08:01 +0200
Subject: [PATCH] Add Possibility to Measure External Batteries via Analog Pin

---
 src/config.h.example | 11 +++++++++++
 src/main.cpp         | 19 +++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/src/config.h.example b/src/config.h.example
index a939ade..4a27ea2 100644
--- a/src/config.h.example
+++ b/src/config.h.example
@@ -26,6 +26,17 @@
  *************************************************************************************************************************/
 // #define BTN_PIN PIN_PC2
 
+/**************************************************************************************************************************
+ * External Battery Monitoring - If EXT_BAT_PIN is set to an analog pin of the ATTiny (e.g.  PB4 or PB5), it will be used
+ * to read the Battery Voltage instead of the internal supply voltage. This can e.g. be used to monitor the voltage of an
+ * LiPo/LiIon cell connected to the Node via the PowerPack. The Devider should not put out more than 2.5V at the
+ * measurement point. Choose high resistor values (e.g. 2x 1MOhm for LiPo/LiIon) to minimize current drain through the
+ * resistors. The Send voltage will be measured voltage at the pin times EXT_BAT_RATIO.
+ *************************************************************************************************************************/
+// #define EXT_BAT_PIN PIN_PB5
+// #define EXT_BAT_RATIO 2
+
+
 /**************************************************************************************************************************
  * Number of active Sensors (used as long as HAS_NO_SENSOR is not enabled)
  * Set to the correct number of enabled sensors below
diff --git a/src/main.cpp b/src/main.cpp
index f68a767..d7687e5 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -220,6 +220,20 @@ void onEvent(ev_t ev) {
 }
 
 // Get Battery Voltage
+#ifdef  EXT_BAT_PIN
+uint16_t readSupplyVoltage() {
+  pinMode(EXT_BAT_PIN, INPUT);
+  analogReference(INTERNAL2V5);
+  ADC0.CTRLD = ADC_INITDLY_DLY256_gc;
+  ADC0_CTRLB = ADC_SAMPNUM_ACC64_gc;
+  uint16_t reading = analogRead(EXT_BAT_PIN);
+  reading = reading/64;
+  DEBUG_PRINT("ADC Reading: ");
+  DEBUG_PRINTLN(reading);
+  reading = (int16_t)(reading * (2500/1024.0) * EXT_BAT_RATIO);
+  return reading;
+}
+#else
 uint16_t readSupplyVoltage() { //returns value in millivolts to avoid floating point
   uint16_t temp = 0;
   analogReference(VDD);
@@ -233,6 +247,7 @@ uint16_t readSupplyVoltage() { //returns value in millivolts to avoid floating p
   reading = intermediate / temp;
   return reading;
 }
+#endif
 
 // Read Sensors and Send Data
 void do_send(osjob_t* j) {
@@ -305,6 +320,10 @@ void setup()
   for (int i = 0; i < (sizeof(disabledPins) / sizeof(disabledPins[0])) - 1; i++)
     pinMode(disabledPins[i], INPUT_PULLUP);
 
+  #ifdef EXT_BAT_PIN
+    
+  #endif
+
   // Setup WS2812B LEDs
   #ifdef WS2812B_PIN
     pinMode(WS2812B_PIN, OUTPUT);