@themusicman This means that something else in OSX is access the USBport via a terminal preventing M5Burner from being able to access the port.

Please make sure only M5Burner is running and that no other terminal software is running.

I tried on my MacBookPro (original issue was on iMac) with no other serial terminal software running, exactly the same issues unfortunately. I have now returned the M5Core2 device back to thePiHut and am awaiting a replacement.

Thanks for your support though @ajb2k3 - it is much appreciated.

Please make sure only M5Burner is running and that no other terminal software is running.

I tried this earlier too, these are the results of trying that... any suggestions?

esptool.py v3.3.2-dev
Serial port /dev/tty.wchusbserial54FC0182651
Traceback (most recent call last):
File "/Applications/M5Burner.app/Contents/Resources/packages/tool/serial/serialposix.py", line 265, in open
self.fd = os.open(self.portstr, os.O_RDWR | os.O_NOCTTY | os.O_NONBLOCK)
OSError: [Errno 16] Resource busy: '/dev/tty.wchusbserial54FC0182651'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/Applications/M5Burner.app/Contents/Resources/packages/tool/esptool.py", line 5399, in <module>
_main()
File "/Applications/M5Burner.app/Contents/Resources/packages/tool/esptool.py", line 5392, in _main
main()
File "/Applications/M5Burner.app/Contents/Resources/packages/tool/esptool.py", line 4699, in main
esp = esp or get_default_connected_device(ser_list, port=args.port, connect_attempts=args.connect_attempts,
File "/Applications/M5Burner.app/Contents/Resources/packages/tool/esptool.py", line 110, in get_default_connected_device
_esp = ESPLoader.detect_chip(each_port, initial_baud, before, trace,
File "/Applications/M5Burner.app/Contents/Resources/packages/tool/esptool.py", line 363, in detect_chip
detect_port = ESPLoader(port, baud, trace_enabled=trace_enabled)
File "/Applications/M5Burner.app/Contents/Resources/packages/tool/esptool.py", line 320, in init
self._port = serial.serial_for_url(port)
File "/Applications/M5Burner.app/Contents/Resources/packages/tool/serial/init.py", line 88, in serial_for_url
instance.open()
File "/Applications/M5Burner.app/Contents/Resources/packages/tool/serial/serialposix.py", line 268, in open
raise SerialException(msg.errno, "could not open port {}: {}".format(self._port, msg))
serial.serialutil.SerialException: [Errno 16] could not open port /dev/tty.wchusbserial54FC0182651: [Errno 16] Resource busy: '/dev/tty.wchusbserial54FC0182651'