Add board loop hook for periodic work

examples/simple_repeater/main.cpp

@@ -165,6 +165,8 @@ void loop() {
     command[0] = 0;  // reset command buffer
   }
 
+  board.loop();   // let the board feed its watchdog, run periodic housekeeping
+
 #ifdef ETHERNET_ENABLED
   ethernet_loop_maintain();
   if (ethernet_read_line(ethernet_command, sizeof(ethernet_command))) {