Add the following to void loop ().

void loop() {
M5.update();
if(M5.BtnA.wasPressed()){M5.Lcd.setRotation(3);M5.Lcd.fillScreen(TFT_BLACK);analogMeter();}
if(M5.BtnC.wasPressed()){M5.Lcd.setRotation(1);M5.Lcd.fillScreen(TFT_BLACK);analogMeter();}