Looking for info on the internal workings of the 41's IR printer module

[emece67]

Hi all,

I'm aware of the IR protocol used by hp's IR printers, and also aware that the ROM for the IR printer module is available. But, has anybody a clue about the hardware inner workings of such module? How does the 41 control the IR LED? Does the nut processor directly access the LED or has the module some counters/timers to do so?

I've searched the forum (and also the documents in TOS) to no avail.

Thanks & regards.

[Monte Dalrymple]

(05-06-2016 04:51 PM)emece67 Wrote:  Hi all,

I'm aware of the IR protocol used by hp's IR printers, and also aware that the ROM for the IR printer module is available. But, has anybody a clue about the hardware inner workings of such module? How does the 41 control the IR LED? Does the nut processor directly access the LED or has the module some counters/timers to do so?

I've searched the forum (and also the documents in TOS) to no avail.

Thanks & regards.

I expect that the IR module contains either a microcontroller or an ASIC to implement the IR protocol and drive the LED. Given the frequencies involved the 41 CPU cannot be doing it directly. I have always been curious about this also, but I am too cheap to take apart my module to see what's inside.

[damaltor]

+1 on that. I have the tools and the knowledge to rebuild one i guess, as i made an usb interface for casio basic calcs before, but i dont have one to disassemble. Any info is appreciated.

[emece67]

I do have one IR module, but I guess that opening it will not give any clue about its workings. All I expect to see is a chip under a epoxy blob and a LED.

[Hans Brueggemann]

in some ancient FW versions of FRAM71, i had the IR printer hardware layer implemented to calculate the error-correction bits and the data framing in hardware.
what i can say for sure is that the HP-41C doesn't drive the IR LED directly. the LED is driven by the module hardware. also, the module contains a 32.768 kHz XTAL as a timebase for the data frames.
   

[damaltor]

That is interesting. Its time for me to learn more about the 41's internals...

[J-F Garnier]

(05-09-2016 08:00 AM)Mike (Stgt) Wrote:  Is there an HP41-Emulator that runs Blinky's firmware in some useful way?

I once tried to trace the code to understand how it works.
Below are my notes ... not sure it's useful for you...

J-F

----------

IR ROM uses:
DATA registers 20 to 2D seems implemented with only one byte.
They are used in the TESTP function, are they elsewhere??
Seem to be the same registers than the peripheral ones.

smart perf 9 (same than 82143 printer, but with different opcodes):
14 registers 0 to D (same than the one accessed through DATA20-2D?)
opcodes are:
RDPTRN n
CH= cmd

to write C[1-0] into register n (0<n<D), the sequence is used:
SELPF 9
CH =nE

to read register n (0<n<D) into C[1-0]:
SELPF 9
RDPTRN n
CH= 01

Combined sequence:
6833 264 SELPF 9
6834 138 CH= 4E (78)
6835 1FA RDPTRN 7
6836 005 CH= 01 (1)
This writes C into reg4 and read reg7 into C