Adds MAX17048 battery monitor support.

Author: Rob

src/batterymonitor.cpp

@@ -43,11 +43,17 @@ void BatteryMonitor::Setup()
         m_Logger.error("MCP3021 not found on I2C bus");
     }
 #endif
+#if BATTERY_MONITOR == BAT_MAX17048
+    if (address == 0)
+    {
+        m_Logger.error("MAX17048 not found on I2C bus");
+    }
+#endif
 }
 
 void BatteryMonitor::Loop()
 {
-    #if BATTERY_MONITOR == BAT_EXTERNAL || BATTERY_MONITOR == BAT_INTERNAL || BATTERY_MONITOR == BAT_MCP3021 || BATTERY_MONITOR == BAT_INTERNAL_MCP3021
+    #if BATTERY_MONITOR == BAT_EXTERNAL || BATTERY_MONITOR == BAT_INTERNAL || BATTERY_MONITOR == BAT_MCP3021 || BATTERY_MONITOR == BAT_INTERNAL_MCP3021 || BATTERY_MONITOR == BAT_MAX17048
         auto now_ms = millis();
         if (now_ms - last_battery_sample >= batterySampleRate)
         {
@@ -99,6 +105,20 @@ void BatteryMonitor::Loop()
                     }
                 }
             #endif
+            #if BATTERY_MONITOR == BAT_MAX17048
+                if (address > 0)
+                {
+                    // Cell voltage register address 0x02
+                    uint16_t data;
+            		auto status = I2Cdev::readWord(address, 0x02, &data);
+                    if (status == 0)
+                    {
+                        float v = data * (78.125 / 1000000);
+                        voltage = (voltage > 0) ? min(voltage, v) : v;
+                        m_Logger.info("MAX17048 voltage %f", voltage);
+                    }
+                }
+            #endif
             if (voltage > 0) //valid measurement
             {
                 // Estimate battery level, 3.2V is 0%, 4.17V is 100% (1.0)

src/batterymonitor.h

@@ -74,10 +74,9 @@ class BatteryMonitor
 
 private:
     unsigned long last_battery_sample = 0;
-#if BATTERY_MONITOR == BAT_MCP3021 || BATTERY_MONITOR == BAT_INTERNAL_MCP3021
-    // TODO: The Feather has a MAX17048 (or LC709203F on older ones) 
-    // uint8_t address = 0x36;
-    uint8_t address = 0;
+#if BATTERY_MONITOR == BAT_MCP3021 || BATTERY_MONITOR == BAT_INTERNAL_MCP3021 || BATTERY_MONITOR == BAT_MAX17048
+    // The Feather has a MAX17048 at 0x36 (LC709203F is used on older boards though) 
+    uint8_t address = 0x36;
 #endif
 #if BATTERY_MONITOR == BAT_INTERNAL || BATTERY_MONITOR == BAT_INTERNAL_MCP3021
     uint16_t voltage_3_3 = 3000;

src/consts.h

@@ -62,6 +62,7 @@
 #define BAT_INTERNAL 2
 #define BAT_MCP3021 3
 #define BAT_INTERNAL_MCP3021 4
+#define BAT_MAX17048 5
 
 #define LED_OFF 255
 

src/defines.h

@@ -56,7 +56,9 @@ IMU_DESC_ENTRY(IMU_BMP160, PRIMARY_IMU_ADDRESS_ONE, IMU_ROTATION, PIN_IMU_SCL, P
 //   BAT_EXTERNAL for ADC pin,
 //   BAT_INTERNAL for internal - can detect only low battery,
 //   BAT_MCP3021 for external ADC connected over I2C
-#define BATTERY_MONITOR BAT_INTERNAL
+//   BAT_MAX17048 for the MAX17048 LiPo fuel gauge connected over I2C
+// #define BATTERY_MONITOR BAT_MAX17048
+#define BATTERY_MONITOR BAT_MAX17048
 
 // BAT_EXTERNAL definition override
 // D1 Mini boards with ESP8266 have internal resistors. For these boards you only have to adjust BATTERY_SHIELD_RESISTANCE.