Add temperature unit conversion

Selects unit based on OSD unit system setting: metric is degC and
imperial is degF.

src/main/io/osd.c

@@ -207,6 +207,26 @@ static int32_t osdGetMetersToSelectedUnit(int32_t meters)
     }
 }
 
+STATIC_UNIT_TESTED int osdConvertTemperatureToSelectedUnit(int tempInDeciDegrees)
+{
+    switch (osdConfig()->units) {
+    case OSD_UNIT_IMPERIAL:
+        return ((tempInDeciDegrees * 9) / 5) + 320;
+    default:
+        return tempInDeciDegrees;
+    }
+}
+
+static char osdGetTemperatureSymbolForSelectedUnit(void)
+{
+    switch (osdConfig()->units) {
+    case OSD_UNIT_IMPERIAL:
+        return 'F';
+    default:
+        return 'C';
+    }
+}
+
 static void osdFormatAltitudeString(char * buff, int altitude, bool pad)
 {
     const int alt = osdGetMetersToSelectedUnit(altitude);
@@ -762,7 +782,7 @@ static bool osdDrawSingleElement(uint8_t item)
 
 #ifdef USE_ADC_INTERNAL
     case OSD_CORE_TEMPERATURE:
-        tfp_sprintf(buff, "%02dC", getCoreTemperatureCelsius());
+        tfp_sprintf(buff, "%02d%c", osdConvertTemperatureToSelectedUnit(getCoreTemperatureCelsius() * 10) / 10, osdGetTemperatureSymbolForSelectedUnit());
         break;
 #endif
 

src/test/unit/osd_unittest.cc

@@ -52,6 +52,7 @@ extern "C" {
     void osdRefresh(timeUs_t currentTimeUs);
     void osdFormatTime(char * buff, osd_timer_precision_e precision, timeUs_t time);
     void osdFormatTimer(char *buff, bool showSymbol, int timerIndex);
+    int osdConvertTemperatureToSelectedUnit(int tempInDeciDegrees);
 
     uint16_t rssi;
     attitudeEulerAngles_t attitude;
@@ -753,6 +754,9 @@ TEST(OsdTest, TestElementCoreTemperature)
     // given
     osdConfigMutable()->item_pos[OSD_CORE_TEMPERATURE] = OSD_POS(1, 8) | VISIBLE_FLAG;
 
+    // and
+    osdConfigMutable()->units = OSD_UNIT_METRIC;
+
     // and
     simulationCoreTemperature = 0;
 
@@ -772,6 +776,16 @@ TEST(OsdTest, TestElementCoreTemperature)
 
     // then
     displayPortTestBufferSubstring(1, 8, "33C");
+
+    // given
+    osdConfigMutable()->units = OSD_UNIT_IMPERIAL;
+
+    // when
+    displayClearScreen(&testDisplayPort);
+    osdRefresh(simulationTime);
+
+    // then
+    displayPortTestBufferSubstring(1, 8, "91F");
 }
 
 /*
@@ -905,6 +919,16 @@ TEST(OsdTest, TestFormatTimeString)
     EXPECT_EQ(0, strcmp("01:59.00", buff));
 }
 
+TEST(OsdTest, TestConvertTemperatureUnits)
+{
+    /* In Celsius */
+    osdConfigMutable()->units = OSD_UNIT_METRIC;
+    EXPECT_EQ(osdConvertTemperatureToSelectedUnit(330), 330);
+
+    /* In Fahrenheit */
+    osdConfigMutable()->units = OSD_UNIT_IMPERIAL;
+    EXPECT_EQ(osdConvertTemperatureToSelectedUnit(330), 914);
+}
 
 // STUBS
 extern "C" {