from what you’ve posted there are several problems:
- the “available ports” element just looks up the available ports registered in the system registry (somewhere here: HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\SERIALCOMM), so if there’s a port connected, it will show up there. However, that doesn’t mean the port is open.
You probably just forgot the “open port” element. or just forgot it in this definition.
your acceleration is near to double what is considered a good input, which means your motor starts extremely slow. I would try and stick with the minimal recommendation.
having 2 nema 17 (and probably 12V on the H-bridges) on the cnc shield can heat up your arduino, mostly when you keep the motors torgue (break). this means that the not very stable serial port connection that tends to loose some bits might be failing after a minute because the pairing fails and there’s no automatism to doublecheck lost values if not implemented manually, which I assume has not been done in firefly.
however, if you had it run for like a minute without problems, it’s not very probable that the problem comes from the first two points, but from hardware config… I’d try additional cooling at the arduino, smaller motors, less than 12V or a timer component to automatically reset the quad stepper element in case it stops working correctly.