Hacking cartridge HP 84/85

[Wonko]

The teensy 4.0 was released a few weeks ago. It is faster by a factor factor of 100 over the 3.2. Not sure if that is true for all operations, especially DMA, which seems to be the solution here.

[dragonator]

I did see the 4.0, which made me very happy. However, for DMA it should indeed not make much of a difference, only the handling around DMA. I have a library to write a sequence to one or two ports over DMA for the Teensy 3.2. I hope to alter that to write to the HP84 in a few weeks. The library was already tested and works, but it needs some of the kinks worked out. With the 4.0 It seems reasonable that you might bitbang it.

[maxt]

I'm wondering if the teensy 4.0, being so much faster, still makes DMA a requirement for faster printing with the HP45.
Maybe the current firmware just becomes fast enough ?

[dragonator]

I'm wondering if the teensy 4.0, being so much faster, still makes DMA a requirement for faster printing with the HP45.
Maybe the current firmware just becomes fast enough ?

Not the right thread for a full discussion, but better, but probably not completely. The HP45 takes 1.8us to fire a single pulse, and requires 66 pulses for each burst. Without any other overhead this means that just in delays, each burst takes 120us. Because of the time sensitive nature of the pulse, nothing else is done in this time. DMA makes it so that the microcontroller is not involved in a burst, freeing up the time for other tasks like fetching new lines from serial and updating position. The same story mostly applies to the HP84, where with the Teensy 4.0 you would be bitbanging a 2 data line shift register with minimal clock widths and the same time sensitive pulse. Of course everything would get better with a faster microcontroller, and things would certainly be faster, But I fear that it will not replace or come close to a DMA system (or even better, an FPGA system).

I guess I will find out when I do finally try a Teensy 4.0. I do actually like the idea of just adding a 4.0 and see how fast I can suddenly go.

[Wonko]

How reliable are the latest drafts on this really nice printhead? Are the voltages correct? I saw some of the timings, but what are the chance of them working? I hate to see MAsic12345 struggle on the software side after he did such nice research on the hardware side, but it is so difficult to help across the distance and across media.

I was trying to get a printer with this setup, so I could verify the signals, but either they were above $500, or looked like junk. I wasted $200 on one that switched on twice and then pretty much died. I would invest into a head/cartridge combo, even thiough they are expensive when original, but not into another printer.

Would it make sense to create a single page that sums up all findings, including a level of confidence? Is a forum a good place for that or is a Wiki/community-editable-page the better platform (but a spam magnet)? Maybe a public Google doc?

[MAsic12345]

I checked everything 10 times, even the engine connected it turns out it is controlled by a PWM signal
Voltages measured with an oscilloscope accuracy plus minus 10 millivolts

Would it make sense to create a single page that sums up all findings, including a level of confidence? Is a forum a good place for that or is a Wiki/community-editable-page the better platform (but a spam magnet)? Maybe a public Google doc?

I think this is a good idea and can come up with something

[MAsic12345]

By the way, someone faced such a problem
I ordered teensy 4.0
made an order on the official website
registered the order for mail confirmation came
(that the order is accepted)
but the money was not taken from the card and received no answer
ordered to Poland
who knows what it is connected with or where I can find in Europe teensy 4.0

[Wonko]

Mouser is international, including Poland. And they do sell the Teensy series:
https://pl.mouser.com/ProductDetail/Spa ... cgQAvD_BwE

[dragonator]

In the Netherlands there are several resellers that carry them as well. I usually buy them there.

[MAsic12345]

In the Netherlands there are several resellers that carry them as well. I usually buy them there.

have a page?