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Astar 32u4 dev/tty port name question

My Astar32u4 mini has always defined the boot port to be /dev/tty.usbmodem14401 since 2018 until now. Now, after fumbling up on a boot reload yesterday I found the boot port has been defined to be /dev/tty.usbmodem14201. I fixed my avrdude port to be that and all was ok. Now this morning, after doing make clean and make, the boot port changed to /dev/tty.usbmodem142401.

I’m using a makefile straight from the LUFA library that contains:

program: $(TARGET).hex
	avrdude -p $(MCU) -C $(AVRDUDE_CONF) -c $(AVRDUDE_PROGRAMMER) -P $(AVRDUDE_PORT) -U flash:w:$(TARGET).hex

Can you explain, or point me to a document that tells how the boot device is defined?


Hello, Ken.

I am not aware of any document that explains how macOS assigns serial port names to USB serial devices. For devices that do not have a serial number, like the A-Star 32U4 bootloader, the name seems to depend on what physical USB port the device is plugged into. The name might be different while the A-Star 32U4 is running your LUFA code.