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DM42 with homemade printer

Posted: Fri Sep 25, 2020 8:27 pm
by dk-
Hi,

I got my DM42 the other day and I'm very pleased with it. Since I don't have a HP printer I cobbled together my own:
Image

I've had to use the printer modules default font for text since it was too slow to send the text. I'll have to do some translation to get the correct symbols, but other than that it seems to work.

Regards,
Daniel

Re: DM42 with homemade printer

Posted: Sat Sep 26, 2020 12:19 am
by Michael
Very nice. Congrats!
I've been thinking of this too ...

Re: DM42 with homemade printer

Posted: Sat Sep 26, 2020 12:27 pm
by ijabbott
Michael wrote:
Sat Sep 26, 2020 12:19 am
Very nice. Congrats!
I've been thinking of this too ...
May 2021? :)

Re: DM42 with homemade printer

Posted: Sat Sep 26, 2020 2:24 pm
by Maxdao
Awesome !
Could you please post more details on how you did that, and more pictures ?

Re: DM42 with homemade printer

Posted: Sat Sep 26, 2020 8:02 pm
by chr yoko
Fantastic job ! :shock:

Would you share the work ?

List of parts used into that built (printer model, IR led model, arduino type etc ...)

Software used to decode the Infrared data coming from the DM42/HPs and transcoding it to the printer via USB.

:ugeek:

Re: DM42 with homemade printer

Posted: Sat Sep 26, 2020 8:37 pm
by dk-
Hi all,

The project is not really in a sharing state, but please feel free to look at the code: https://github.com/dankar/redeye

Here's some quick documentation written on the fly:

The Arduino Uno reads input on pin 3. This is either the pure IR signal (32768Hz when transmitting), or just high when a carrier is detected and low when no carrier. To get this to the input pin I used a simple IR transistor and an opamp for amplification of the signal.

The code then does some error correction and processing of the IR data and then finally forwards the data to another arduino for printing. I had to use two arduinos since my code was too slow when both doing interrupts for the IR data and also handling the thermal printer. The data that is sent to the second arduino is either text, or bitmap data, based on what is being printed. I haven't uploaded code for the second arduino yet. I'm hoping to unify this to one device soon, and the code would depend mostly on what thermal printer you are using (I'm using one from Adafruit.)

I'll make sure to update here when I have a more "complete" solution.

Regards

Re: DM42 with homemade printer

Posted: Sat Sep 26, 2020 9:42 pm
by toml_12953
Wouldn't this be a good item for SwissMicros to sell? It would be a great addition to many of their calculators!

Re: DM42 with homemade printer

Posted: Sat Sep 26, 2020 9:54 pm
by c0rpse
Do you think it would be possible to decode to a device that appears to the computer as a usb hid keyboard?
That way you could "print" to a text editor on your computer.

I'm sure the hardest part would be figuring out how to display the graphs.

Re: DM42 with homemade printer

Posted: Sat Sep 26, 2020 11:42 pm
by dk-
c0rpse wrote:
Sat Sep 26, 2020 9:54 pm
Do you think it would be possible to decode to a device that appears to the computer as a usb hid keyboard?
That way you could "print" to a text editor on your computer.

I'm sure the hardest part would be figuring out how to display the graphs.
That should be fairly easy, but I don't think you'd gain much by doing that. You can already get the prints as an image or text directly on the calculator and transfer to your computer.

Re: DM42 with homemade printer

Posted: Sun Sep 27, 2020 2:29 am
by toml_12953
dk- wrote:
Sat Sep 26, 2020 11:42 pm
c0rpse wrote:
Sat Sep 26, 2020 9:54 pm
Do you think it would be possible to decode to a device that appears to the computer as a usb hid keyboard?
That way you could "print" to a text editor on your computer.

I'm sure the hardest part would be figuring out how to display the graphs.
That should be fairly easy, but I don't think you'd gain much by doing that. You can already get the prints as an image or text directly on the calculator and transfer to your computer.
But why have an intermediate step? I may not always have access to a computer. Besides, the nostalgia factor is huge!