feat: TPro - Use function switch leds as charge level indicator when charging

Co-authored-by: Batam <batam@macbook-pro.home>
Port of https://github.com/opentx/opentx/pull/8871

radio/src/targets/taranis/board.cpp

@@ -158,6 +158,43 @@ void boardInit()
   ledGreen();
 #endif
 
+// Support for FS Led to indicate battery charge level
+#if defined(RADIO_TPRO)
+  // This is needed to prevent radio from starting when usb is plugged to charge
+  usbInit();
+  // prime debounce state...
+   usbPlugged();
+
+   if (usbPlugged()) {
+     delaysInit();
+     adcInit(&stm32_hal_adc_driver);
+     getADC();
+     pwrOn(); // required to get bat adc reads
+     storageReadRadioSettings(false);  // Needed for bat calibration
+     INTERNAL_MODULE_OFF();
+     EXTERNAL_MODULE_OFF();
+    
+     while (usbPlugged()) {
+       // Let it charge ...
+       getADC();
+       delay_ms(20);
+       if (getBatteryVoltage() >= 660)
+         fsLedOn(0);
+       if (getBatteryVoltage() >= 700)
+         fsLedOn(1);
+       if (getBatteryVoltage() >= 740)
+         fsLedOn(2);
+       if (getBatteryVoltage() >= 780)
+         fsLedOn(3);
+       if (getBatteryVoltage() >= 820)
+         fsLedOn(4);
+       if (getBatteryVoltage() >= 842)
+         fsLedOn(5);
+     }
+     pwrOff();
+   }
+#endif
+
   keysInit();
 
 #if defined(ROTARY_ENCODER_NAVIGATION)