Have you installed the serial driver for the HP-1? And confirmed the comm port sometimes it puts it on com port 20. Look at device manager once serial driver is installed.
Yes - been running the serial driver with ArcPatrol for a few years, tried the com port in device manager - this laptop has 4 ports, and actually lists each as different. Tried all 4 and reset baud rate each time.
No big deal , I just wanted to verify it with a HP1.