AX-80 O.S. hacking co-op?

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AX-80 O.S. hacking co-op?

Post by rhino » Tue Nov 19, 2013 9:08 pm

Anybody here have the desire and/or skills to work towards developing a new OS for the Akai AX-80 to add Sysex and patch dumping/loading?
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Re: AX-80 O.S. hacking co-op?

Post by garranimal » Wed Nov 20, 2013 3:56 am

Alas, I don't have the skills but this is an interesting proposal. Service manual seems difficult to google. Most of the parameters have low resolution, with the possibility of real-time stepping artifacts. Still, to add computer patch editing and midi transmit/receive would be greatly beneficial.

Would be nice to add a unison mode with detune control. But like the Juno-106, I suspect it uses a master oscillator which makes adding a unison feature a matter of hardware modification.

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Re: AX-80 O.S. hacking co-op?

Post by cornutt » Wed Nov 20, 2013 7:45 pm

garranimal wrote: Would be nice to add a unison mode with detune control. But like the Juno-106, I suspect it uses a master oscillator which makes adding a unison feature a matter of hardware modification.
Not necessarily... there are ways it could have been done on the 106 and not sounded like c**p. I'm not sure why Roland didn't do it; maybe they didn't have enough CPU or code memory.

What CPU does the AX80 use?
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Re: AX-80 O.S. hacking co-op?

Post by rhino » Wed Nov 20, 2013 7:56 pm

uPD7811 - with the internal mask programable ROM bypassed. Quite powerful for its day. IIRC, the same used in the Casio CZ series.

My goal was not to add synth features, just to make a drop-in EPROM chip that would allow sysex editing and patch dump/load by single patch, or bank. As is, the tape storage must save or load both banks A and B all at once.

A poor-mans solution might be a software that could read the tape signal, then break it into the 64 patchs, allow them to be edited, then re-combined into a new .WAV file to be sent back to the AX.
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Re: AX-80 O.S. hacking co-op?

Post by Walter Ego » Wed Nov 20, 2013 11:59 pm

I'm for this, as I recently acquired a beat-up AX-80 for free. I love the look and feel and it has great sounds...getting rid of the lack of Sysex would be great...
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Re: AX-80 O.S. hacking co-op?

Post by tim_m » Mon Feb 10, 2014 8:48 pm

I had started to map out features that I would want for a project like this, but have been seriously sidetracked in life! I was imagining a drop-in CPU replacement that could add the following:

Portamento
Toggling the LFO to be able to run free, as opposed to reset
MIDI/Sysex dump abilities
A legitimate mono mode with detune (I use the 'chord memory, press one key' hack a lot)
Adding a noise oscillator somehow
Being able to independently change the volume of the sub oscillator
Better live filter cutoff control than using the mod wheel with that LFO (it always droops for me)
Better knob resolution?
Better velocity resolution
A more properly scaled resonance control
Press & hold button to edit parameter (as opposed to having to press the 'edit' button)
a more tunable filter key-follow
Perhaps being able to overwrite the ROM patches.

Sadly, I'm years from being to properly address a project like this.

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Re: AX-80 O.S. hacking co-op?

Post by rhino » Tue Feb 11, 2014 2:48 am

Welcome to the board!
I fear such an extensive re-thinking might exceed the value of the synth. I am - however - planing(dreaming) of such a mod on the Korg Poly61.

My intent was to get Sysex working for pach dump/load and an editor/librarian - nothing further. My plan was to simply plug in another EPROM and go.

While searching the web, I chanced upon a fellow who has done reverse-engeneering of the uPD7811 CPU.
He stated in an email that he was busy with other projects at work and did not have time to deal with this, but may soon.

I am an old geezer with years of electronic experence, but am a newbie at writing code. My last attempt was on a RadioShack TRS-80 back in the dim '70's.

Stay tuned. Something may yet come of this. I keep bugging Akai (now owned bu Numark) about a contact with someone who was on the original AX-80 project.....assuming any are still alive!!!
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Re: AX-80 O.S. hacking co-op?

Post by commodorejohn » Tue Feb 11, 2014 3:07 am

The uPD7811 is documented here; there's a datasheet linked that contains an architecture briefing/opcode listing, and instructions on getting an assembler and disassembler from the MAME toolkit. Do you know if the AX-80 uses the 7811's internal ROM or not? That might affect how easy it would be to hack...
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Re: AX-80 O.S. hacking co-op?

Post by tim_m » Tue Feb 11, 2014 5:47 am

rhino wrote:Welcome to the board!
I fear such an extensive re-thinking might exceed the value of the synth.
Thanks! I've been away for some time, and it's good to be back. I'm not necessarily worried about the value of the synth (I paid almost nothing for mine); it's more that I like using the synth a lot, but frequently feel like it's a bit constrained by it's CPU. The other idea I had a while back was to pull out all of the 4558's, and put in something like NE5532's to see if it changed the character of the synth. Thankfully, I never bothered :)
rhino wrote: Stay tuned. Something may yet come of this. I keep bugging Akai (now owned bu Numark) about a contact with someone who was on the original AX-80 project.....assuming any are still alive!!!
Definitely keep up posted. I had always assumed that David Cockerell had something to do with the AX80, but it looks like you may be looking for 'Tamaki San'. This link explains a bit of Akai's past.
commodorejohn wrote:The uPD7811 is documented here; there's a datasheet linked that contains an architecture briefing/opcode listing, and instructions on getting an assembler and disassembler from the MAME toolkit. Do you know if the AX-80 uses the 7811's internal ROM or not? That might affect how easy it would be to hack...
Very interesting!

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Re: AX-80 O.S. hacking co-op?

Post by tim_m » Mon Feb 24, 2014 9:24 pm

I looked a little bit at this over the weekend. Looking at the service manual, there are two 7811G’s - one for key assignment, and the other for ‘program/frequency table’ (IC1 and IC2). I opened my AX80 to confirm, and indeed they are both there, but unfortunately, both aren’t socketed, so it would be difficult to to remove them to use the MAME disassembler.

One prominent looking chip on the CPU board was IC4, a NEC D2764D, with a label on it saying ‘AX80-K’. According to the CPU block diagram in the service manual, IC4 is for ‘ROM 8K Program’. IC4 is socketed for easy removal. IC5 and IC6 (D446C-1’s) are listed as ‘RAM 2KB backup memory’, which I’d guess are the two banks of savable patches.

As for MIDI sysex data, the MIDI interface (IC32) connects functionally to IC2 (the 7811G for ‘program/frequency table’), and the tape interface connects from IC2 to IC27. On a service bulletin, it mentions changing a resistor related to IC2, since there was a problem with parameters in edit mode changing themselves, so my guess is that if there were any method for hacking the AX80 to dump sysex data, IC2 is the best bet to look at...if only it were socketed.

Here’s the diagram for what each pin of what IC2 does. If only it were as easy as sending the patch dump data to pin 17, rather than 24 :)

Image

Additionally, I haven’t figured out if it’s possible to use them, but there are actually unused bars on the displays that could be used for something.

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Re: AX-80 O.S. hacking co-op?

Post by oldsynth » Thu Jun 26, 2014 11:17 pm

Hi gents. I'm desperate to get my Akai AX-80 modified so that the LFO will free-run instead of re-triggering every key press. anybody know how to do this mod? cheers Darron

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Re: AX-80 O.S. hacking co-op?

Post by tim_m » Wed Oct 28, 2015 9:58 pm

Hi everyone, has anyone made any progress with this?

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Re: AX-80 O.S. hacking co-op?

Post by themilford » Wed Oct 28, 2015 11:11 pm

I would be into this for the AX60… having CC and Sysex would be a great upgrade…

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Re: AX-80 O.S. hacking co-op?

Post by Rasputin » Thu Jul 21, 2016 5:30 am

I have neither the time nor inclination to complete this project all by myself, but I have some experience with this CPU and also Tape Out formats.

If anyone is currently working on or planning to tackle this idea then feel free to respond here and I will offer what help and direction I can.

But be warned: If you have no experience with (any form of) Assembly, bitwise logic, and debuggers than this program is unlikely to get off the ground.

This NEC processor isn't as common as the Zilog Z80 or Motorola 68K so it's going to be pretty difficult to find anyone with the skill, motivation and time to do this for free.

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Re: AX-80 O.S. hacking co-op?

Post by commodorejohn » Thu Jul 21, 2016 5:52 am

If someone wants to make a dump of the ROM (IC4) I could at least poke around a little.
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