ajxs 13 hours ago

Author here, thank you for posting this! If anyone has any questions about the article, I'd be happy to answer them!

  • coldpie an hour ago

    Amazing work. I briefly explored trying to RE a more modern piece of hardware, the Tascam Portastudio DP-24SD, in order to try to fix some well-known bugs and limitations. Your article inspired me to maybe give it another go.

    Previously, I managed to decode a firmware update file for the unit, but quickly found out that it uses a special-purpose DSP chip, and I wasn't able to easily find public documentation for its instruction set. So I gave up. Do you have a gut feeling on if REing and hacking this firmware could be done by a dedicated amateur, or is this probably more like professional-level work and I should find something better to do?

  • Rochus 5 hours ago

    Interesting work, thank you. May I ask what you are going to do with it? Do you want to emulate it on a PC, or redesign it to make a VST plugin?

  • mrunkel 11 hours ago

    I just wanted to say thank you. This is a great read.

    • ajxs 6 hours ago

      Thank you! I really appreciate it.

  • platevoltage 10 hours ago

    Very cool! I have a DX7IIFD with an EEPROM in it. It will be cool to see what I can do with this!

mutagen 12 hours ago

Seems like a good place to mention The Usual Suspects, a group that has built emulation of the Motorola DSP5630 and associated hardware to allow playable virtual instruments.

https://dsp56300.wordpress.com/

  • ajxs 6 hours ago

    These guys do amazing work! I wish Korg hadn't beat them to the MicroKorg VST though. I've used the MicroKorg extensively in music over the years, and would have loved an accurate VST. Unfortunately the filter in Korg's VST doesn't quite match the original, and I can't recreate some of my patches. For understandable reasons these guys aren't going to step on Korg's toes and compete with an actual commercial product.

  • grawlinson 10 hours ago

    They've also been working on emulating the JP-8080, as per recent discord announcements.

    The JP-8080 uses custom DSP chips designed by Roland, and Roland do not provide a Virtual Instrument (VST) for this much desired synth.

  • aa-jv 9 hours ago

    These guys are awesome .. their interaction with Kemper&co, about their amazing emulation work, not so much.

    There's a hard lesson for hardware manufacturers to be learned in this drama.

    If Kemper were supportive, they'd have a very clear road to a next-gen Virus TI (a "Proton"?) on the horizon .. but the word on the street has it that they're hostile to the effort of emulating the Motorola DSP ...

    • import 4 hours ago

      Oh wow didn’t know next gen virus is a thing

__alexander 2 hours ago

> All I had when I started was a copy of the firmware, a copy of the service manual, and a can-do attitude

This is how some of the best reverse engineers in the industry got started, especially when it comes to video game cheats.

aa-jv 9 hours ago

Great work, ajxs, been following you for years.

I hope you get a chance to work on some other synths in the future .. would be fun to see you apply your skills to, for example, the UNO synths, or the Arturia *Freaks' .. would be hilarious to see custom firmwares for those modern synths, some day.

  • ajxs 6 hours ago

    Thank you! I really appreciate your support!

    Lately I've been working on the Casio CZ101. Hopefully in the next few weeks I'll publish a partially annotated disassembled firmware on my Github, along with article too talking about its interesting NEC μPD7810G CPU. Mostly because there's almost no other information about the CPU available online, despite featuring in some prominent 80s synths.

    Following Pajen's awesome lead, I poked around inside the Korg Volcas, but I didn't accomplish enough to write about it. A 16KiB EPROM full of hand-crafted 8-bit assembly is a totally different animal to 256KiB of compiler optimised ARM! One modern synth whose firmware I loaded up in Ghidra is the Prophet X: After Espen Kraft's video complaining about it, I thought I'd have a peek inside it for myself. Sequential published the firmware without stripping out the debug symbols, so if anyone else is interested there's a real possibility of progress!

    • ErroneousBosh 6 hours ago

      Oh this is relevant to my interests.

      I've been doing quite a bit of work on the Juno 106 ROMs but haven't really got my head around Ghidra yet. I've just been working from the service manuals for various versions (including the HS-60, which is probably the most complete scan of a manual) and the programming reference for the μPD7810. I notice that all of my Juno boards leave out the EPROM socket and latch that would allow it to run from external ROM - I wonder if there was ever an "upgrade" from an early version?

      https://github.com/ErroneousBosh/j106roms

    • pajen 5 hours ago

      Hey thanks for the shoutout! I loved your article here, it is a wonderful intro to this kind of work. I started the Volca RE work on IDAPro, but moved over to Ghidra later...

    • Supernaut 4 hours ago

      A disassembly of the operating system for the series II Fairlight CMI would be fascinating, I would think.

      Your bio suggests that you live in Sydney, so it would be particularly appropriate for you to examine code that was written in Rushcutters Bay!

throw_m239339 9 hours ago

If someone could help me reverse engineer the Zoom ARQ96 firmware in order to fix the stupid LFO mod amount implementation (LFO is basically unusable), add velocity note control to the step sequencer, and why not, add basic USB MIDI Input recording support, and ideally, a chord mode, it would be great...

https://zoomcorp.com/en/us/digital-instruments/digital-instr...

For the LFO mod amounts I imagine the values are hardcoded somewhere, so it shouldn't be that hard. Adding a new UI for velocity levels or a chord mode would be more complex though. Even better if there was a Zoom engineer around here who could guide me a bit...

  • tweetle_beetle an hour ago

    Did you read the section about what made the DX7 hardware a good target for this project?

    https://ajxs.me/blog/Introduction_to_Reverse-Engineering_Vin...

    The ARQ96 is an incredibly niche product all things considered, but especially compared to the DX7. It's also ~10 years old rather than ~40 years old. It's a completely different beast.

    Zoom released few firmware updates, but v1.x to v2.x was a very significant change. Are you using the latest version?