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Modern thermal printer to emulate 82240B
07-07-2018, 04:52 AM (This post was last modified: 07-07-2018 02:12 PM by tcab.)
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RE: Modern thermal printer to emulate 82240B
(07-06-2018 10:54 AM)Thomas Okken Wrote:  Which printers does this support? Can end users customize it to work with printers that aren't supported by default?

Print42 theoretically supports numerous thermal printers (other than the recommended Epson TM-T20 which I own) because it uses a Python library called python-escpos to do the low level printing, which in turn uses the open source ESC/POS printer database which is a community-maintained database of thermal receipt printer capabilities. For a list of supported printers visit here.

There is a slight complication however in that the virtual printer file that Free42’s generates is unicode (nice) yet most affordable thermal printers do not support unicode. You can of course buy a nice unicode thermal printer but such printers cost much more than traditional thermal printers.

We want to print the full range of Free42 unicode characters on affordable printers. Luckily these traditional thermal printers have multiple codepages, and most of the characters we need can be found. Print42 dynamically switches codepages to emit the needed character.

However more obscure HP-42S characters like ▸←↑↓→≠∫∡ are typically not available on any typical thermal printer codepage. The way I solved this is was to create a custom codepage and load it with custom characters - but this currently only works for Epson printers - since programming such codepages involves vendor specific magic escape codes and custom fonts etc.

This kind of custom font programming could potentially be open sourced and made part of python-escpos and the open source ESC/POS printer database - but that would be a major project in itself, and require the consent of those existing projects. Alternatively I could somehow make a plug in architecture to allow users of Print42 to program their non Epson printers with custom HP-42S fonts. Happy to look at doing this if Print42 gets some usage and there is demand.

To summarise, look at the open source ESC/POS printer database:
  • Unicode thermal printers - ok
  • Epson thermal printers - ok
  • Non Epson printers - 98% ok but probably no ▸←↑↓→≠∫∡ chars, unless they happen to have those characters in one of their codepages, in which case it will be found automatically and you will be ok.

Now for a competently different way of looking at things…

Print42 has a graphics mode where it looks for Free42’s GIF virtual tape files. This mode is compatible with any thermal printer in the aforementioned ESC/POS printer database, as there are no fonts/characters involved - just pure graphics. This mode exactly replicates Free42 output and thus is suitable for graphs etc. Graphics mode doesn't have quite all the same features as text mode e.g. no search.

Final recommendation:

I have only tested with the Epson TM-T20. I can’t buy lots of different thermal printers and test with them all, so will need to rely on others to provide feedback over time. If you are buying a new thermal printer I simply suggest buying an Epson, as it is the only brand with Mac, Windows and Linux drivers, and you can also use it as a normal system printer from all your other apps (e.g. Word, Excel, Notepad, Pages, terminal etc.)

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RE: Modern thermal printer to emulate 82240B - tcab - 07-07-2018 04:52 AM

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