Reply To: Low Cost EC sensor Station upgrade

The access is denied error doesn’t mean the Mayfly is off, it means something else (another program or window on your computer) is monopolizing that serial port. Usually you see it when you try to upload a program or start a serial port monitor when another serial port monitor was already running.

If you have the Mayfly plugged directly into the USB of your computer and the Mayfly is off, the error is more to the effect that the serial port doesn’t exist, not access is denied. If you’re using something like an ftdi friend between the Mayfly and your computer, you’ll see avrdude sync errors if the Mayfly is off.