add standby with display stub

src/main.cpp

@@ -26,6 +26,8 @@
 #include <sys/time.h>
 #include "apps/sntp/sntp.h"
 
+#include "driver/rtc_io.h"
+
 #include "main.h"
 #include "hardware.h"
 #include "mp3.h"
@@ -242,6 +244,7 @@ void suspend(uint32_t secondsToSleep) {
     u8g2.setFont(u8g2_font_inb19_mf);
     u8g2.drawStr(0, 20, timeStr);
     // ToDo: set rtc gpio resistors
+    rtc_gpio_hold_en((gpio_num_t)16);
     esp_sleep_enable_timer_wakeup(1000000LL * 60);
   }