using old HP82240B "red-eye" printers

[victorf]

Several years ago I purchased 6 NIB HP82240B printers. These printers were used to provide hard-copy output from HP48 Calculators. I was looking for a thermal printer to use in some of my early micro projects and I still am. It was my intention to develop a "device" that would convert standard '232 serial output to the IR protocol required to drive the printer. I was never clever enough to do this!. I suspect that I never will be.

I have quite a bit of technical documentation relating to the HP IR protocol and would like to know if such a protocol converter could be built.

Any enlightenment will be appreciated.

[dlh]

Looks simple enough if this article is accurate.

http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=74

[victorf]

dlh,

Thanks for pointing me to that article. I have added it to my HPIR archives. Now I have to get the October 1997 HP Journal article as well.

Simple for you but basically Greek to me. I have no idea how to even get started with implementing this sort of stuff.

Is the ZX an appropriate device to use?
How would all this half bit times and burst stuff be implemented?

Any further enlightenment will be greatly appreciated.

Vic

[dlh]

It's all explained in the article I cited. The IR Carrier frequency is 32,768Hz and all of the bit times are derived from that frequency using cycles of carrier rather than time. I haven't looked at it in detail but it appears to use Manchester encoding.

I usually use a PIC to generate an IR carrier as it's easy to turn the PWM on and off to create the bursts but you can probably do this using PulseOut. At 32.768kHz a single cycle is 1/32768 or 30.5µS. A 15.25µS pulse followed by a 15.25µS space gives you 1 cycle of carrier. It need not be exact as the IR receivers generally have a ±3kHz (or more) bandwidth. You use this signal to drive an IR emitter diode (IRED).

I have suggested to Don that a function to generate IR carrier bursts defined in cycles of carrier would be a useful addition but he never responded. At about the same time he lost some email messages and that may have been one of them. CCF codes (Philips Pronto) are defined this way. It would make the ZX very useful for IR remote control.

While this is not directly applicable to your project, this document is very helpful in understanding IR remote control in general. http://www.remotecentral.com/features/irdisp1.htm