Calculators with Support of the 82240 IR-Printer

[Martin Hepperle]

(06-25-2014 07:38 PM)everettr Wrote:  Hi,
I was just thinking about doing the same thing, using an Arduino nano.
What sort of IR detector did you use? I am looking at Mouser part # 782-TSOP34833.
Were you able to use or adapt a published Arduino IR library to decode the HP protocol? I have seen an HP article on the origins of the protocol, but have no idea if it is anything like current IR remote control protocols.

A device like this ought to be really useful for uploading programs from a 42s to a PC, assuming anyone would still want to do something like that.

Hello,

without giving much thought or research, I had ordered a small IR-receiver board from China, mounted with 2 condensers and 2 resistors as per datasheet - just right for tinkering with the Arduino. It came with a VS1838B, which is probably the same as a TSOP1383B. This chip is for 38 kHz, which is relatively far away from the nominal 32.768 kHz of the HP spec, but this seems to be less critical - my unit works very well also over several meters with a HP 48G (per datasheet it should have a reduced receptivity of about 50% compared to a 32kHz receiver). Reading through some sources, I learned that some detectors detect signals only with 10 and more bursts, while the HPs per definition send 6-8 bursts. This seems to a be critical factor, so you should make sure you select a receiver designed for 6 or more bursts, NOT 10.
So I would recommend to select a 33 kHz receiver for 6+ pulses, e.g. a TSOP1833 chip (33 kHz, 6+ pulses), but the 1830, 1836, 1837 1838 might also work well enough).

I did not use any Arduino libraries except for the Serial output library as it is more fun to develop and understand something than just using black box stuff. I also used i/o and timer interrupts to implement the time critical parts, which leads to a relatively large code size when using Arduino libs. The resulting code is about 5 kBytes including 1 bit error checking, which should be okay to put it in a small chip directly at the end of a USB-TTL cable. Or in a small printer or whatever device is of interest. I also want to add some ESCape sequences to control e.g. power outlets etc. The printer specs leaves some room here without harming the printer function.
After finishing the developing on the Leonardo, I want to put the code into a Nano or Micro as a final solution. An Arduino with USB/Serial (like the Pro) can be directly used as a IR->Serial adapter or you can even simulate a keyboard using your pocket calculator.

I just finished the first version of the code and can make it available if you are interested. I am just adding some comments so that the code is understandable.

Martin