Light pen protocol reverse engineered

Light pen protocol reverse engineered

by sd_snatcher on 13-09-2015, 15:55
Topic: Hardware

The light pen protocol, up until known a big question mark in everyone's mind, was finally reverse engineered, and the information about it is published in the MSX wiki article. Now it can be emulated, or even newer devices can be built based on the standard. With the help of Erik Luppes of, who donated a rare Sanyo MLP-001 lightpen, Brazilian MSX user sd_snatcher was able to research, reverse engineer and document his findings for all of you.

Relevant link: Light pen in the MSX wiki

Comments (4)

By djh1697

Paragon (1615)

djh1697's picture

14-09-2015, 23:55

Shame it could not be made to work with a TFT monitor, I used to have one but sold it.... perhaps now I get regrets! Still a fellow UK MSXer is sending me a disk less MSX2. but I will not be collecting again Wink

By SLotman

Paragon (1239)

SLotman's picture

15-09-2015, 20:54

It was my dream in the 80s/90s to have a lightpen. But it wasn't sold *anywhere* here in Brazil, even if there were magazines ads showing it :/

And nowadays, if you don't have a CRT TV, they're practically useless (as light guns are too, which is a shame) Sad

By Pac

Scribe (6553)

Pac's picture

18-09-2015, 19:13

Congratulations, we know that this device is not very popular (maybe even not useful nowadays Question ) anyway thank you for your research and dedication, our MSX knowledge is now better Wink .

By djh1697

Paragon (1615)

djh1697's picture

26-09-2015, 23:08

I recall writing a BASIC program for MSX1 that involved drop down menus and the light pen. It used IN and OUT commands, to return coordinates of where the lightpen pressed on the screen, my knowledge was vague on the matter these days. My thoughts when programming the lightpen where "this isn't to MSX standards", since the MSX BIOS manual tell you not to access the ports directly.