Hacking cartridge HP 84/85

[MAsic12345]

Thanks bigbomber
while I can’t write everything in detail because I didn’t finish everything completely
pinout brush the latest image of pinout is current

[Wonko]

After having helped you over the last 16 pages, it would really be nice to get a little bit more information on the protocols and timing. I'll check the most recent pinout, but I am pretty sure that this is not enough to replicate your success

[MAsic12345]

Well this weekend I’ll try to describe how we did it and how it works

[MAsic12345]

Hello forum ytec3d and users
Here are the achievements we have achieved
The print head works ignoring 14 and 15 pins I couldn’t figure out what they were doing or what they were responsible for.
1,2,3,4. Ignore their contacts, they won’t need them

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the protocol works with seven bit clocks with a frequency of 3 megahertz
one row of nozzles corresponds to one data pin
one row of nozzles is divided into 7 groups
each bit corresponds to its own nozzle group
I haven’t experimented with the groups yet and don’t know how to turn on one nozzles only groups are included
For the nozzles to work, I had to make 900 cycles of seven-bit data strips in code

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developed a voltage inclusion circuit controlling teensy 4.0
Caution, if the load power exceeds 1 Ampere, the print head will burn.
the power source must regulate the load and install no more than one ampere

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[MAsic12345]

I can share the code, but it does not fit too many characters. What options are there?
Here is the circuit board in the assembly
I took the carriage from the printer, soldered the cable there and connected it to the board.
there are extra 4 PCBs if someone is interested

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[dragonator]

Thank you for sharing this. I will see if I can replicate this over the next few weeks. You have made a nice summary.

For sharing code, you can zip it and add it as an attachment. We might not be able to read it in the forum, but we can at least use it.

Looking at the voltages, I have to assume that the 12V is for driving the addresses, and the 9V is for driving the primitives. The 9V pads are substantially bigger. I would add a heatsink on your design on the 5V regulator that drives your teensy and the 9V regulator. Depending on the input voltage I suspect these can get quite hot. 9V @ 1A from a supply voltage of 18V means that the component is disipating 9W.

[Wonko]

Thank you very much for summing up all your findings! This is really cool.

[MAsic12345]

And here is the code

[dragonator]

I do finally have the time, and now that you have shared this, I finally bought an HP84 myself. I do hope I can find a few days around Christmas to mess with this. First thing I will make is a connector so I can wire this up.

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[dragonator]

I made a connector that holds pogo pins. I will also make an ink supply and a suction cup, and then I can test whether I can send lines to it.

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