feat: update PowerManagement voltage calculation logic

hal/ArduinoHAL.h

@@ -28,6 +28,7 @@ using String = std::string;
 #define INPUT 0
 #define HIGH 1
 #define LOW 0
+#define ADC_VOLTAGE 192
 
 inline void pinMode(int pin, int mode) { //NOLINT
     // Do nothing
@@ -37,6 +38,18 @@ inline void digitalWrite(int pin, int value) { //NOLINT
     // Do nothing
 }
 
+inline void analogReadResolution(int bits) {
+    // Do nothing, we will just return a 12-bit value in analogRead
+}
+
+inline uint32_t analogRead(int pin) {
+    // Return a dummy 12 bit value for the voltage pin, and 0 for other pins. 
+    // This allows us to test the battery voltage reading functionality without needing a real ADC.
+    if (pin == ADC_VOLTAGE) {
+        return static_cast<uint32_t>((1 << 12) - 1); // Return full-scale value for a 12-bit ADC
+    }
+    return 0; // Default dummy value for other pins
+}
 
 // millis mock which still gives us the time since the program started in milliseconds
 static auto program_start = std::chrono::high_resolution_clock::now();

include/PowerManagement.h

@@ -1,50 +1,64 @@
 #ifndef PowerManagement_H
 #define PowerManagement_H
 
-#include "Arduino.h"
-#include "pins.h"
+#include "ArduinoHAL.h"
 
 /**
  * @brief Simple ADC-based battery voltage helper.
- * @note When to use: quick health checks of the main battery using an analog
- *       pin and known divider scaling.
+ * This class provides a way to read the battery voltage using an ADC pin and a scaling factor.
+ * 
+ * The correct pin can be found in the hardware scematics under "ADC_VOLTAGE"
+ * and the scaling factor can be calculated based on the voltage divider used in the hardware design. 
+ * For MARTHA 1.4, the voltage divider is 200k and 1k5, so the factor is (200k + 1k5) / 1k5 = 134.33333.
+ * 
+ * The voltage at the pin is calculated as:
+ * vPin = (rawValue / (2^numAdcBits - 1)) * vRef
+ * where rawValue is the ADC reading, numAdcBits is the resolution of the ADC, and vRef is the reference voltage for the ADC (3.3V for MARTHA 1.4).
+ * The battery voltage is then calculated as:
+ * vBat = vPin * factor
  */
 class BatteryVoltage {
     public:
-        BatteryVoltage(uint8_t adcPin, float conversionFactor)
-            : pin(adcPin), factor(conversionFactor) {}
+        /**
+         * @param adcPin The ADC pin connected to the battery voltage divider.
+         * @param factor The scaling factor to convert the pin voltage to battery voltage.
+         * @param numAdcBits The resolution of the ADC (e.g., 12 for 12-bit ADC).
+         * @param voltageThreshold A threshold voltage for low battery checks (not used in current implementation but can be useful for future extensions).
+         */
+        BatteryVoltage(uint8_t adcPin, float factor, int numAdcBits, float voltageThreshold)
+            : pin(adcPin), factor(factor), numAdcBits(numAdcBits), voltageThreshold(voltageThreshold) {analogReadResolution(numAdcBits);}
 
         /**
          * @brief Sample the ADC and convert to battery voltage.
          * @return Converted voltage reading.
-         * @note When to use: periodic health checks or brownout warnings.
          */
         float readVoltage() {
             // Set the pin for reading
             pinMode(pin, INPUT);
-            uint32_t rawValue = 0;
-            rawValue = analogRead(pin);  // Should give a value between 0 and 1023, not sure how to convert this to the true voltage. 
-            // Conversion notes ->  respect to Vref you would do Vref * analogRead()/2^12. 
-            // After that you can use the voltage divider equation to get the battery voltage level
-            // Vref is 134.33? 
-            // float voltage = pow((rawValue/2),12) * factor; 
-            Serial.println(rawValue);
-            return rawValue;
+            uint32_t rawValue = analogRead(pin);  // Should give a value between 0 and 2^numAdcBits - 1
+            float vRef = 3.3f; // reference voltage for the ADC on MARTHA 1.4
+
+            // Convert raw ADC value to voltage at the pin, then apply the factor to get battery voltage
+            float vPin = (static_cast<float>(rawValue) / (static_cast<float>(1 << numAdcBits) - 1)) * vRef;
+            float vBat = vPin * factor;
+
+            return vBat;
         }
 
         /**
          * @brief Check whether voltage exceeds a minimal threshold.
          * @return true if voltage is above the survival threshold.
-         * @note When to use: lightweight go/no-go checks before more detailed
-         *       power analysis.
+         * @note Could be useful for future extension, like triggering a low power mode
          */
-        bool isAlive(){
-            return readVoltage() > .3; // Not sure what a good cutoff is 
+        bool isLow(){
+            return readVoltage() < voltageThreshold;
     }
 
     private:
         uint8_t pin;
         float factor;
+        int numAdcBits;
+        float voltageThreshold;
     };
 
     #endif // PowerManagement_H