5.b. Determining serial port names in Mac OS X
To use the programmer in Mac OS X, you will need to determine which names have been assigned to its serial ports.
To do this, open a Terminal window, type
ls /dev/tty.usb*, and press enter. You should see two entries of the form tty.usbmodem<number> (e.g.
/dev/tty.usbmodem00022331). These entries represent virtual serial ports created by the programmer.
The entry with the lower number is your programmer’s Programming Port, and later you will need to pass its name as a parameter to AVRDUDE. The entry with the higher number (which should be two plus the lower number) is the TTL Serial Port, and you can use a terminal program such as
screen to send and receive bytes from it.
If you have other USB devices plugged in, you might see additional serial ports for those devices.