Switched 'v_bat' and 'charge' fields of state struct from float to, respectively, uint16_t and uint8_t and updated UI functions accordingly. Rationale for this change is providing better support for future platforms without hardware floating point unit.

openrtx/include/interfaces/graphics.h

@@ -288,7 +288,7 @@ void gfx_printError(const char *text, fontSize_t size);
  * @param height: battery icon height
  * @param percentage: battery charge percentage
  */
-void gfx_drawBattery(point_t start, uint16_t width, uint16_t height, float percentage);
+void gfx_drawBattery(point_t start, uint16_t width, uint16_t height, uint8_t percentage);
 
 /**
  * Function to draw Smeter of arbitrary size.

openrtx/include/state.h

@@ -69,8 +69,8 @@ typedef struct
 {
     bool radioStateUpdated;
     curTime_t time;
-    float v_bat;
+    uint16_t v_bat;
-    float charge;
+    uint8_t charge;
     float rssi;
 
     uint8_t ui_screen;

openrtx/src/graphics.c

@@ -561,13 +561,13 @@ void gfx_printError(const char *text, fontSize_t size)
  *
  */
 void gfx_drawBattery(point_t start, uint16_t width, uint16_t height,
-                                                    float percentage)
+                                                    uint8_t percentage)
 {
     color_t white =  {255, 255, 255, 255};
     color_t black =  {0,   0,   0  , 255};
 
     // Cap percentage to 1
-    percentage = (percentage > 1.0f) ? 1.0f : percentage;
+    percentage = (percentage > 100) ? 100 : percentage;
 
 #ifdef PIX_FMT_RGB565
     color_t green =  {0,   255, 0  , 255};
@@ -576,9 +576,9 @@ void gfx_drawBattery(point_t start, uint16_t width, uint16_t height,
 
     // Select color according to percentage
     color_t bat_color = yellow;
-    if (percentage < 0.3)
+    if (percentage < 30)
         bat_color = red;
-    else if (percentage > 0.6)
+    else if (percentage > 60)
         bat_color = green;
 #elif defined PIX_FMT_BW
     color_t bat_color = white;
@@ -589,8 +589,8 @@ void gfx_drawBattery(point_t start, uint16_t width, uint16_t height,
 
     // Draw the battery fill
     point_t fill_start = {start.x + 2, start.y + 2};
-    gfx_drawRect(fill_start, (int)(((float)(width - 4)) * percentage),
+    int fillWidth = ((width - 4) * percentage) / 100;
-                 height - 4, bat_color, true);
+    gfx_drawRect(fill_start, fillWidth, height - 4, bat_color, true);
 
     // Round corners
     point_t top_left = start;

openrtx/src/threads.c

@@ -225,9 +225,14 @@ void *dev_task(void *arg)
         state.time = rtc_getTime();
 #endif
 
-        // Low-pass filtering with a time constant of 10s when updated at 1Hz
+        /*
-        float vbat = platform_getVbat();
+         * Low-pass filtering with a time constant of 10s when updated at 1Hz
-        state.v_bat = 0.02*vbat + 0.98*state.v_bat;
+         * Original computation: state.v_bat = 0.02*vbat + 0.98*state.v_bat
+         * Peak error is 18mV when input voltage is 49mV.
+         */
+        uint16_t vbat = platform_getVbat();
+        state.v_bat  -= (state.v_bat * 2) / 100;
+        state.v_bat  += (vbat * 2) / 100;
 
         state.charge = battery_getCharge(state.v_bat);
         state.rssi = rtx_getRssi();

openrtx/src/ui/ui.c

@@ -363,7 +363,7 @@ void _ui_drawLowBatteryScreen()
     uint16_t bat_width = SCREEN_WIDTH / 2;
     uint16_t bat_height = SCREEN_HEIGHT / 3;
     point_t bat_pos = {SCREEN_WIDTH / 4, SCREEN_HEIGHT / 8};
-    gfx_drawBattery(bat_pos, bat_width, bat_height, 0.1f);
+    gfx_drawBattery(bat_pos, bat_width, bat_height, 10);
     point_t text_pos_1 = {0, SCREEN_HEIGHT * 2 / 3};
     point_t text_pos_2 = {0, SCREEN_HEIGHT * 2 / 3 + 16};
 

openrtx/src/ui/ui_menu.c

@@ -188,10 +188,16 @@ int _ui_getInfoValueName(char *buf, uint8_t max_len, uint8_t index)
             snprintf(buf, max_len, "%s", GIT_VERSION);
             break;
         case 1: // Battery voltage
-            snprintf(buf, max_len, "%.1fV", last_state.v_bat);
+        {
+            // Compute integer part and mantissa of voltage value, adding 50mV
+            // to mantissa for rounding to nearest integer
+            uint16_t volt  = last_state.v_bat / 1000;
+            uint16_t mvolt = ((last_state.v_bat - volt * 1000) + 50) / 100;
+            snprintf(buf, max_len, "%d.%dV", volt, mvolt);
+        }
             break;
         case 2: // Battery charge
-            snprintf(buf, max_len, "%.1f%%", last_state.charge * 100);
+            snprintf(buf, max_len, "%d%%", last_state.charge);
             break;
         case 3: // RSSI
             snprintf(buf, max_len, "%.1fdBm", last_state.rssi);

platform/drivers/baseband/radio_MD3x0.cpp

@@ -387,7 +387,7 @@ float radio_getRssi()
     if(rxFreq < 401035000) offset_index = 0;
     if(rxFreq > 479995000) offset_index = 8;
 
-    float rssi_mv  = adc1_getMeasurement(ADC_RSSI_CH);
+    float rssi_mv  = ((float) adc1_getMeasurement(ADC_RSSI_CH));
     float rssi_dbm = (rssi_mv - rssi_offset[offset_index]) / rssi_gain;
     return rssi_dbm;
 }