Images on 9front
KX P3124
The printer itself speaks PCL (Printer Control Language) and that has been easy enough to figure out. To send images, I have been using:
ESC + '*' + m + nL + nH + data
to send a line of bits to the print head for printing.
m = an arbitrary byte which sets the dot density
nL = (number of dot-columns) % 256
nH = (number of dot-columns) / 256
data = bytes of data to print. 1 bit=1 dot
I started with the Raspberry Pi, which is easy enough to set up a 9front CPU server on. However, 9front has no usblp drivers. While writing drivers is an eventual goal of mine, in order to avoid scope-creep, I decided to just use a x86_64 computer with a parallel port.
After installing 9front to the server however… the parallel port was not appearing in /dev/. I found the parallel port in the /sys/src/9/pc directory, but not in the pc64 directory. I asked about it on IRC and sigrid recommended I check pc64. Lo, there, under devices, was # lpt. I uncommented and rebuilt the kernel. Now I have /dev/lpt2data. The number depends on the port see /sys/src/9/pc/devlpt.c
Now, I just needed to be able to write to it. The following imports the printer to 9front on my laptop:
#!/bin/rc
rimport -b 192.168.0.102 '#L2' /dev
Piping text to it has the expected result: text is printed. I really wanted to figure out images though. My programming is a little rusty so I read through a manual for PCL ESC+’*’, and read a bunch of 9front manuals, and looked through other image software. Eventually, I found what I wanted: memdraw(2). I did it wrong a few times, and didn’t account for extra bytes in memdraw, but, eventually I had a working tool which took a plan9 image on stdin and sent out PCL on stdout.
It’s very WIP, but the version as of 2024/06/29 is included here:
Next step: