Add battery presence LEDs

Author: Codex Agent

README.md

@@ -46,6 +46,8 @@ HeatControl is a dual-zone heating control system for drysuit diving, based on E
 - `GPIO1` -> ADC voltage input 2 (`ADC_PIN_2`)
 - `GPIO3` -> MOSFET 1 NTC ADC input (`ADC_PIN_NTC_MOSFET_1`)
 - `GPIO4` -> MOSFET 2 NTC ADC input (`ADC_PIN_NTC_MOSFET_2`)
+- `GPIO8` -> Battery 1 presence LED (`BATTERY_LED_PIN_1`)
+- `GPIO9` -> Battery 2 presence LED (`BATTERY_LED_PIN_2`)
 - `GPIO20`/`GPIO21` -> UART0 reserved (left free by firmware)
 - `GPIO18`/`GPIO19` -> Native USB reserved (left free by firmware)
 - `GPIO2`/`GPIO8`/`GPIO9` -> Strapping pins; do not use for fixed voltage-divider inputs

src/app_state.cpp

@@ -16,6 +16,8 @@ bool lastHeater1State = false;
 bool lastHeater2State = false;
 bool lastSignalPinState = false;
 bool lastInputPinState = false;
+bool lastBatteryLed1State = false;
+bool lastBatteryLed2State = false;
 bool manualHeater1Enabled = true;
 bool manualHeater2Enabled = true;
 bool battery1Off = false;

src/app_state.h

@@ -50,6 +50,12 @@ constexpr int ADC_PIN_NTC_MOSFET_2 = 4;
 constexpr int ONE_WIRE_BUS = 7;
 constexpr int AP_MAX_CLIENTS = 4;
 
+// Battery presence LEDs (active HIGH).
+// Note: GPIO8/GPIO9 are ESP32-C3 strapping pins. Using them as OUTPUT is usually fine,
+// but make sure the external LED circuit does not pull them to a boot-incorrect level.
+constexpr int BATTERY_LED_PIN_1 = 8;
+constexpr int BATTERY_LED_PIN_2 = 9;
+
 // Keep UART0 free on final PCB for external flashing/debug adapter.
 constexpr int UART0_RX_RESERVED_PIN = 20;
 constexpr int UART0_TX_RESERVED_PIN = 21;
@@ -99,6 +105,8 @@ extern bool lastHeater1State;
 extern bool lastHeater2State;
 extern bool lastSignalPinState;
 extern bool lastInputPinState;
+extern bool lastBatteryLed1State;
+extern bool lastBatteryLed2State;
 
 extern bool manualHeater1Enabled;
 extern bool manualHeater2Enabled;

src/main.cpp

@@ -220,10 +220,14 @@ void setup() {
   pinMode(SSR_PIN_2, OUTPUT);
   pinMode(INPUT_PIN, INPUT_PULLDOWN);
   pinMode(SIGNAL_PIN, OUTPUT);
+  pinMode(BATTERY_LED_PIN_1, OUTPUT);
+  pinMode(BATTERY_LED_PIN_2, OUTPUT);
 
   digitalWrite(SSR_PIN_1, LOW);
   digitalWrite(SSR_PIN_2, LOW);
   digitalWrite(SIGNAL_PIN, HIGH);
+  digitalWrite(BATTERY_LED_PIN_1, LOW);
+  digitalWrite(BATTERY_LED_PIN_2, LOW);
 
   // ADC setup (ESP32-C3): 12-bit readings, extended input range.
   analogReadResolution(12);
@@ -237,6 +241,8 @@ void setup() {
   lastHeater2State = (digitalRead(SSR_PIN_2) == HIGH);
   lastSignalPinState = (digitalRead(SIGNAL_PIN) == LOW);
   lastInputPinState = (digitalRead(INPUT_PIN) == HIGH);
+  lastBatteryLed1State = (digitalRead(BATTERY_LED_PIN_1) == HIGH);
+  lastBatteryLed2State = (digitalRead(BATTERY_LED_PIN_2) == HIGH);
 
   const uint8_t savedBootMode = getAndClearBootMode();
   if (savedBootMode == BOOT_MODE_NORMAL) {
@@ -428,6 +434,24 @@ void loop() {
     const bool batt2OffNow = batt2Sample.offNow;
     const bool batt2OnNow = batt2Sample.onNow;
 
+    // Battery presence LEDs: ON when battery is stably detected as ON.
+    // Avoid flicker in the hysteresis band by only updating on stable ON/OFF.
+    if (batt1OnNow && !lastBatteryLed1State) {
+      lastBatteryLed1State = true;
+      digitalWrite(BATTERY_LED_PIN_1, HIGH);
+    } else if (batt1OffNow && lastBatteryLed1State) {
+      lastBatteryLed1State = false;
+      digitalWrite(BATTERY_LED_PIN_1, LOW);
+    }
+
+    if (batt2OnNow && !lastBatteryLed2State) {
+      lastBatteryLed2State = true;
+      digitalWrite(BATTERY_LED_PIN_2, HIGH);
+    } else if (batt2OffNow && lastBatteryLed2State) {
+      lastBatteryLed2State = false;
+      digitalWrite(BATTERY_LED_PIN_2, LOW);
+    }
+
     // Persist last known battery presence mask (bit0 = battery1, bit1 = battery2)
     // only when it changes, to avoid unnecessary EEPROM wear.
     uint8_t currentMask = 0;