Who wants a new printing HP-42s?

[ziggurat29]

(06-18-2017 02:20 AM)mfleming Wrote:  Check out the document by Martin Hepperle at this link
http://www.mh-aerotools.de/hp/red-eye/
Having built this project, I can attest to the relative ease of construction and availability of parts. An Arduino Pro Mini decodes the Redeye IR protocol and outputs the received characters over its serial port. All that is missing is a function to convert the Redeye characters to those the printer can handle.
The IR receiver/transmitter unit is a bit harder to find and a bit more expensive, but I'm sure someone can come up with a suitable replacement design!
~Mark

Thanks for the link; actually, that should be child's play with a couple tweaks:

1) if you're going this route, forget about the USB version of the printer, just get the serial version. They still make those, and its so much easier to interface with from a microcontroller. If you were to do this, then you could probably use a 'blue pill' board (about usd $2-3 on ebaty). (That board is not suitable for USB hosting, alas, because it has an 'F103 processor. It would need an 'F105, though you could rebrain it since those are pin-compatible.)

2) I myself would not have used the external IR adapter. Their point is well-made regarding the TSOP-xxx devices -- coincidentally I had done the same a couple days ago(!) for an unrelated activity involving an 82240 printer -- but they actually can work if you're careful. But really, making the receiver circuit from scratch is pretty trivial, too: IR encapsulated phototransistor, some passives, and maybe a schmidt trigger. (I had to do this myself for the aforementioned project since I needed to see the raw, modulated, signal, rather than the integrated-and-shaped-up one).