Updating HoTT GPS Altitude code to match spec.

Unit test added.

src/telemetry_hott.c

@@ -171,8 +171,10 @@ void hottPrepareGPSResponse(HOTT_GPS_MSG_t *hottGPSMessage)
     hottGPSMessage->home_distance_L = GPS_distanceToHome & 0x00FF;
     hottGPSMessage->home_distance_H = GPS_distanceToHome >> 8;
 
-    hottGPSMessage->altitude_L = GPS_altitude & 0x00FF;
-    hottGPSMessage->altitude_H = GPS_altitude >> 8;
+    uint16_t hottGpsAltitude = (GPS_altitude / 10) + HOTT_GPS_ALTITUDE_OFFSET; // 1 / 0.1f == 10, GPS_altitude of 1 == 0.1m
+
+    hottGPSMessage->altitude_L = hottGpsAltitude & 0x00FF;
+    hottGPSMessage->altitude_H = hottGpsAltitude >> 8;
 
     hottGPSMessage->home_direction = GPS_directionToHome;
 }

src/telemetry_hott.h

@@ -27,6 +27,8 @@
 #define HOTT_EAM_OFFSET_M3S          120
 #define HOTT_EAM_OFFSET_TEMPERATURE   20
 
+#define HOTT_GPS_ALTITUDE_OFFSET 500
+
 typedef enum {
     HOTT_EAM_ALARM1_FLAG_NONE = 0,
     HOTT_EAM_ALARM1_FLAG_MAH = (1 << 0),
@@ -476,4 +478,7 @@ void configureHoTTTelemetryPort(void);
 void freeHoTTTelemetryPort(void);
 
 uint32_t getHoTTTelemetryProviderBaudRate(void);
+
+void hottPrepareGPSResponse(HOTT_GPS_MSG_t *hottGPSMessage);
+
 #endif /* TELEMETRY_HOTT_H_ */

test/telemetry_hott_unittest.cc

@@ -109,6 +109,22 @@ TEST(TelemetryHottTest, UpdateGPSCoordinates3)
     EXPECT_EQ((int16_t)(hottGPSMessage->pos_EW_sec_H << 8 | hottGPSMessage->pos_EW_sec_L), 9999);
 }
 
+TEST(TelemetryHottTest, PrepareGPSMessage_Altitude1m)
+{
+    // given
+    HOTT_GPS_MSG_t *hottGPSMessage = getGPSMessageForTest();
+
+    f.GPS_FIX = 1;
+    uint16_t altitudeInMeters = 1;
+    GPS_altitude = altitudeInMeters * (1 / 0.1f); // 1 = 0.1m
+
+    // when
+    hottPrepareGPSResponse(hottGPSMessage);
+
+    // then
+    EXPECT_EQ((int16_t)(hottGPSMessage->altitude_H << 8 | hottGPSMessage->altitude_L), 1 + HOTT_GPS_ALTITUDE_OFFSET);
+}
+
 
 // STUBS
 
@@ -166,6 +182,8 @@ serialPort_t *openSerialPort(serialPortFunction_e functionMask, serialReceiveCal
     UNUSED(callback);
     UNUSED(mode);
     UNUSED(inversion);
+
+    return NULL;
 }
 
 serialPort_t *findOpenSerialPort(uint16_t functionMask) {