Summary:

Printing to physical printer is now working with both the GoojPrt and APS EPM203-MRS units.

I am now moving onto optimizations and enhancements.

Deets:

I implemented two physical printer rasterizers for two of the sample printer cores: the GoojPrt unit that I was originally going to use, and the APS EPM203-MRS unit that I got later. They both print correctly (with some caveats):

APS EPM203-MRS output is top two, GoojPrt output is lower two. So, printing is a-happinin'! Yay!

There are two caveats, though:

1. as mentioned earlier, the electrical design of the GoojPrt leaves some things to be desired. As you can see in those two printouts, the output is rather faint. This is easily addressed with a command that specifies heating/resting times for the thermal head, but using that so far has only resulted in power supply droops that reset the printer, so I am holding off on addressing that now until I get a better power supply. I find this annoying, but the code must go on!
2. also as mentioned earlier, the APS unit's firmware has the annoying tendency of advancing the paper when printing bitmaps (and everything in this printer project is treated as bitmaps so as to realize the 82240 character sets). You can see the effect in the top right printout, where there is noticeable space between the lower printed 'lines'. Those are on separate strips of output bitmap. It doesn't look incredibly horrible here, but that is just good luck. If I were to print, say, a graph, then you would see the intervening paper advances.
   
   That printer happens to have a 'reverse linefeed' command, which in principle I could use to compensate, but the maddening thing is that the gratuitous paper advance only happens if there is a pause in the print data stream greater than some unknown amount (around a second or less). If the pause is below that threshold, there is no advance. You can see this in the top lines of that printout, where the successive rendered bitmaps (three in that case) are output in rapid succession.
   
   This is maddening to me. I am scouring the datasheet to see if this is some feature that can be turned off. I may disassemble the printer's firmware to see if I can find a way to stop it (I disassembled the firmware of the Kashino last week for an unrelated activity).

So, now I am trying to fix the power supply issue for the Gooj, and the gratuitous paper advance issue for the APS. After resolving those, the project will technically be 'done', but is anything really ever 'done'?

As mentioned before, as an enhancement, I want to implement a command-line interface 'monitor' program that runs on the USB side. It would do things like manage settings and whatnot.

As an additional feature, I want to be able to realize some secondary functionality such as:

• send decoded IR to USB port; this would realize an HP82240 to PC adapter for receiving raw data from the calculator for... whatever!
• forward data from USB to printer port; this would realize an PC to thermal receipt printer adapter
• etc.

After that, I should be able to mark the project 'completed'. My favorite task to cross off!

Next:

I want to resolve the annoying paper advance issue in the APS printer, and the annoying power suck issue in the GoojPtr.

I need to capture a video of the printer in operation for the blog.