A new old bug in the printer ROM?

[Tinue]

Thank you for this inside view on the development of the DM41X! The fact that it supports printing at all is amazing; I really love this calculator and have great fun playing around with it.

What I like in the 82242A ROM (based purely on reading its manual) is that it can be switched to support the 82240A natively (with MAPOFF), and then one can also e.g. enable underline printing, or start the self test from the calculator. I didn't really think about it and assumed that there is some sort of serial interface to the IR hardware of the 82242A module that could be simulated, but as you explain it is much more complicated.

Meanwhile I found an older project on Github that converts an Arduino into a Red Eye infrared sender, and with the help of this I can send any data that I like from my computer to see how the printer behaves.