Fix for PWM tone in transmission

driver/backlight.c

@@ -34,7 +34,7 @@ bool backlightOn;
 void BACKLIGHT_InitHardware()
 {
 	// 48MHz / 94 / 1024 ~ 500Hz
-	const uint32_t PWM_FREQUENCY_HZ =  1000;
+	const uint32_t PWM_FREQUENCY_HZ =  4000;
 	PWM_PLUS0_CLKSRC |= ((48000000 / 1024 / PWM_FREQUENCY_HZ) << 16);
 	PWM_PLUS0_PERIOD = 1023;
 
@@ -154,4 +154,4 @@ void BACKLIGHT_SetBrightness(uint8_t brigtness)
 uint8_t BACKLIGHT_GetBrightness(void)
 {
 	return currentBrightness;
-}
+}