PC to HP 48G infrared communication

[Christoph Giesselink]

The problem here maybe the ckermit program on the PC. When sending bytes over the IR port you may get IR reflections, that means that the byte you send is also received by your receiver. That's normally no problem, after sending the byte you just clear your receive buffer and you're ready to receive the answer of your request. The HP48 kermit implementation know this, so the IR transfer between two HP48 is no problem.

Most PC kermit programs don't clear the receive buffer after sending, because at a cable transfer they aren't aware about IR reflections.

Where I know from the reflections? The HP48 has an IR selftest and on a HP48GX/SX you can remove the port housing an so the cover over the IR transmitter. With removed housing/cover the IR selftest fails, but not with the mounted cover. The reasons are the IR reflections on the cover.