Hacking the HP45

Powder and inkjet printing
davidk
Posts: 77
Joined: Sun Mar 12, 2017 6:48 pm

Re: Hacking the HP45

Post by davidk »

Regarding L6452, I will tie ADCK and ONENABLE to 5V and CONVSTART, CRDATA, CRLOCK and CRLATCH to GND. ADCK should be tied to VCC because it's active on falling edge. I don't think it's important but I don't need the ADC control logic to be in any kind of initialising anything.
Still, we would appreciate David's experience with it. Did he use these pins?
david
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Re: Hacking the HP45

Post by david »

Sorry guys for my slow response. I'm dragged into a low cost closed loop stepper project, so my progress on HP45 driver will be suspended for a while.

I'm not sure if the company would allow me to reveal the details of the schematics and the firmware for the moment. However, I'm happy to share the general ideas.

1. The Vs(Vsetup) is supposed to drive the DMOS fets. It should not be over 28V and it should be 11V above Vh. I connect it currently to Vpwr(19V) and it seems ok. There still needs two more tests: a) min voltage above Vh, where either the DMOS drops to the linear area or the latency of the DMOS on/off has been adversely affected; b) max voltage above Vh when the gate of DMOS will be broke down (one L6452 may be destroyed for this test).

2. I connected all unused inputs to the ground for easy routing.

3. CD4504 should be ok for the address driving. However, such CD4000 ics are not normally ESD enhanced. So for the the cartridge interface, extra ESD protection is recommended. NB. L6452 is protected to 4kv ESD. it is not very tough, but ok for most cases.

Enjoy the fun of HP45 and please post back anything you'll get, even the mess of the ink on your desk. :-D
davidk
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Re: Hacking the HP45

Post by davidk »

Thank you, David, for your posts here. You determined us to research into using this ST chip and I appreciate this. Your advices are very appreciated.
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dragonator
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Re: Hacking the HP45

Post by dragonator »

After what felt like months (was probably a couple of weeks) I got the PCB's for the standalone. I will start soldering this week. If I find no nasty surprises I might have the basics working in a week.
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dragonator
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Re: Hacking the HP45

Post by dragonator »

Now I may or may not have assembled this thing in one go, going for longer than I myself deem responsible, but it is 95% soldered right now. Only photo's now (I need bed). Testing this weekend. Also, hand assembly of the HP45 connector sucks. Those pins are really tiny.
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david
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Re: Hacking the HP45

Post by david »

the PCB stack looks awesome. BTW, how did you fix the HP45 contact block? did you just tap M3 thread on the block?
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dragonator
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Re: Hacking the HP45

Post by dragonator »

The connector has a hole of around 2.8, so M3 taps into it without much trouble. I hope that it holds, it being only 0.2mm of thread diameter, but I so far it is fine. The plastic is reinforced with glass, so it is quite tough.

Currently the buck converters are working mostly fine. The variable regulator is a lower voltage than expected, but that can be fixed with a different resistor. It is currently on a trim potmeter. Only when I have the system working as good as the old one will I replace it with the digital potmeter, and make that work. The 12V regulator does get warm, even in idle, but I have attached a fan to it for now. I have been told that this is a mismatched inductor. I will fix this in the future, for now it is good enough.

I have gotten the display and navigation switch to work. In the video below is me messing about with the screen a little to get a feel for it. It is not yet running on the full SPI. The screen is on SPI1, and almost all libraries are written for only SPI0 (most microcontrollers only have 1 to begin with). When I get to that, I will probably modify the library and include other functions as well (DMA is on the list).

The carrier has not yet got a clamping mechanism, but I have a few that I am working on.

A small list of things I want to do.
  • Get basic information displayed on the screen. Maybe, maybe not, make a menu structure already.
  • Get the inkjet to work using the old code I have written.
  • Add the digital potmeter and write the code so it will work.
  • Implement the temperature sensing on the printhead. I can finally read the onboard resistors using a voltage divider.
  • Somewhere along the way, start work on the interface with a computer. I have not yet planned this part out yet, but I have 3 ways of talking with the controller. SPI, Serial and the USB port (Also serial).
  • Start working with DMA on the teensy 3.6. This will by far be the most difficult task, but I think I can fire at least a pulse (1 address) and maybe a full burst (all addresses) without the processor working on it by using the Teensy 3.6 DMA channels. This will be a challenge, because there is no library or guide. All I have is the datasheet of the Teensy 3.6 microcontroller. This will take quite a while and will first be tested with my breadboard teensy as a proof of concept. All knowledge I get for DMA here will also probably be applied to the display and the SPI and serial inputs I have planned for external interfacing.
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davidk
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Re: Hacking the HP45

Post by davidk »

Hi,

I started testing my design using ST L6452 with the schematic I show few post ago. Good news, the LT1930 outputs 19V for Vboost and all voltages are correct. The air is clear, no smoke released :-) . So I can start coding the ATMEGA64.
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math
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Re: Hacking the HP45

Post by math »

@davidk

Can you give me some information about this card in the picture?
davidk
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Re: Hacking the HP45

Post by davidk »

Hi math,

I posted a few posts ago the schematic. The only mistake is the 19V output of LT1930 should go to VStepUp and Vr to 12V. If you read the schematic you'll understand. I made a simple firmware to test the pins output, no real test with a cartridge yet.
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