From 5f1141399f95792e1795362bd2ec2240f7e282c752de1a79330067886f64f287 Mon Sep 17 00:00:00 2001
From: localhorst <localhorst@mosad.xyz>
Date: Sun, 9 Nov 2025 17:58:54 +0100
Subject: [PATCH] get battery reference voltage

---
 main.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 62 insertions(+), 4 deletions(-)

diff --git a/main.c b/main.c
index d7f6aee..b9cb86b 100644
--- a/main.c
+++ b/main.c
@@ -76,13 +76,13 @@ int main(void)
     PORTA.PIN0CTRL = PORT_PULLUPEN_bm; // Pull-up enabled
 
     leds_off();                // Ensure all LEDs off at startup
-    battery_level_indicator(); // TODO: Implement
 
     bool bLedEnabledOld = bLedEnabled;
     eModeCurrent = ANIMATION_BLINK; // Set the mode to start with
 
     while (true)
     {
+        battery_level_indicator();
         bBtnPressed = handleSwitch(); // Check switch state
 
         // Light LEDs while button is pressed
@@ -162,6 +162,7 @@ static inline void switchMode(void)
  */
 static void configureLowPower(void)
 {
+    return;
     // Set unused pins as outputs LOW to prevent floating inputs
     // Floating inputs can cause extra current consumption
     PORTA.DIRSET = PIN4_bm | PIN5_bm; // Set PA4, PA5 as outputs if unused
@@ -248,15 +249,72 @@ static inline void leds_on(void)
     setPWM_PA2(255U);
 }
 
+/**
+ * @brief Read battery voltage using internal 1.1V reference
+ * @return Estimated battery voltage in millivolts
+ */
+uint16_t readBatteryVoltage(void)
+{
+    // Enable ADC
+    ADC0.CTRLA = ADC_ENABLE_bm;
+
+    // Select internal voltage reference as input
+    ADC0.MUXPOS = ADC_MUXPOS_INTREF_gc;
+
+    // Use VCC as reference (default)
+    ADC0.CTRLC = ADC_PRESC_DIV4_gc; // Prescaler for 5MHz/4 = 1.25MHz ADC clock
+
+    // Start conversion
+    ADC0.COMMAND = ADC_STCONV_bm;
+
+    // Wait for conversion complete
+    while (!(ADC0.INTFLAGS & ADC_RESRDY_bm))
+        ;
+
+    uint16_t adcResult = ADC0.RES;
+
+    // Disable ADC to save power
+    ADC0.CTRLA = !ADC_ENABLE_bm;
+
+    // Calculate VCC voltage
+    // V_battery = 1.1V × 1023 / ADC_result
+    // Result in millivolts: 1100 × 1023 / ADC_result
+    uint32_t voltage_mv = (1100UL * 1023UL) / adcResult;
+
+    return (uint16_t)voltage_mv;
+}
+
 /**
  * @brief Battery monitoring
  */
 static void battery_level_indicator(void)
 {
-    // TODO: Implement
-    VPORTA.OUT |= (PA6_SET_MASK | PA7_SET_MASK); // green + red OFF
-}
+    uint16_t voltage = readBatteryVoltage();
 
+    // 1S LiPo voltage ranges:
+    // Good: >=3700mV
+    // Low:  >=3500mV
+
+   // VPORTA.OUT &= ~(PA6_SET_MASK | PA7_SET_MASK); // Turn off both LEDs first
+
+    if (voltage >= 3700)
+    {
+        // Green ON, Red OFF - Good battery
+        VPORTA.OUT &= ~PA6_SET_MASK; // Green ON (active low)
+    }
+    else if (voltage >= 3500)
+    {
+        // Both ON (yellow/orange) - Medium battery
+        VPORTA.OUT &= ~(PA6_SET_MASK | PA7_SET_MASK);
+    }
+    else
+    {
+        // Green OFF, Red ON - Low battery
+        VPORTA.OUT &= ~PA7_SET_MASK; // Red ON (active low)
+    }
+
+    VPORTA.OUT &= ~(PA6_SET_MASK | PA7_SET_MASK);
+}
 /**
  * @brief Handle momentary switch input on PA0
  *