Total rework of simulator for dev branch. Create separate thread for interrupt processes. Tick-accurate simulation of timers. Non-blocking character input for running in realtime mode. Decouple hardware sim from grbl code as much as possible. Expanded command line options. Provisions for cross-platform solution.

spindle_control.c

@@ -60,6 +60,7 @@ void spindle_run(uint8_t direction, float rpm)
   if (sys.state == STATE_CHECK_MODE) { return; }
   
   // Empty planner buffer to ensure spindle is set when programmed.
+  protocol_auto_cycle_start(); 
   protocol_buffer_synchronize(); 
 
   // Halt or set spindle direction and rpm.