Relatively Universal ROM Programmer

Relatively Universal ROM Programmer – Project Update!

I’m so thrilled about the progress we’ve made on the Relatively Universal ROM Programmer! This tool has become indispensable for so many, and I couldn’t have done it without all of you. From retro computing enthusiasts to synth tinkerers and breadboard experimenters, your enthusiasm and feedback have been incredible. Hearing how this project is being used worldwide is what makes working on it so rewarding.

Updates and Improvements

Revision 2: Immediate Sell-Out and Feedback!

Revision 2 of the programmer sold out almost immediately, thanks to the overwhelming interest. Alongside the new demand came fantastic feedback, with some ideas already making their way into the latest updates.

Fixing the Feedback Loop and Voltage Control

Special thanks to Kuba0040, who highlighted a potential issue with the feedback loop potentiometer on Revision 2. If the potentiometer is overturned, the wiper might lift, potentially causing a runaway condition in the regulator. While rare, this issue has been fixed by connecting the bottom of the pot to the wiper, making the design more robust.

Video:

On top of that, the feedback loop discussion opened up new possibilities for better control of the output voltage. While off-the-shelf DACs like I2C or SPI exist, they can cost more than the entire board—less than ideal for an affordable, open-source project. Instead, we’re exploring using an 8-bit DAC built with parallel registers, just like the ones already on the programmer. This approach is cost-effective and opens the door for digitally controlling the programming voltage.

For now, Revision 2.1 includes some solder jumper pads on the back of the board, allowing for easier adjustment of the voltage regulator feedback loop. Whether you need a higher default voltage (up to 25V for TMS2532-style ROMs) or want to experiment with digital control, the pads make it straightforward.

Fused Regulator

Revision 2.1 also includes a polyfuse on the programming voltage regulator input. The fuse, rated for 200mA, provides enough power for programming old ROMs while protecting the regulator and the ROM in the socket from accidental shorts. While it’s not foolproof (e.g., a reverse-inserted ROM might still cause damage), it’s a step in the right direction to keep the magic smoke inside.

Firestarter Firmware Updates

A big shoutout to Henrik Olsson, whose work on the Firestarter firmware and app has expanded compatibility to even more ROM types. With the latest updates, Firestarter now supports Flash-based ROMs like the SST39SF series, including the 4Mbit SST39SF040s, with software write protection built-in. Amazing work, Henrik!

What’s Next?

Digital voltage control is on the horizon, but it’s a few prototypes away from perfection. For now, Revision 2.1 is your go-to if you need a reliable programmer for old ROMs. The improvements make it more robust and user-friendly, even if we’re not yet fully digital.

Why Choose the Relatively Universal ROM Programmer?

Sure, commercial programmers like the TL866-II or T48 might be faster for certain tasks, but this project is about openness, repairability, and community. If something breaks, you can fix it. Plus, the ongoing community support makes this much more than just a tool—it’s a platform for experimentation and learning.

Rev 2.1 is for sale over @ iMania.dk for less than $9.

I'm blown away by the success of my little project here! 

The Youtube audience liked it so much it sold out the first time over the first weekend, and by the looks of it the second batch will sell out tomorrow. 

Who would've thunk a 9$ E(E)PROM programmer would be popular? :)

I guess it does help that it now has actual software that'll take a ROM file via serial and burn it - and even has a few standalone features for identifying a ROM etc. 

I say it better in this video...

I'm super happy to announce boards are now on the way - I'm also a bit scared they won't work, but at least in theory they should work. 
And if they do, that will officially make them the cheapest 21V EPROM programmer on the planet @ < 10$ 🎉👾

Anyway, here's how they're supposed to work: 

Things are moving along and I managed to program both a W27C512 and a M2732A - the latter requires a 21V programming pulse, so if we can program that, we're probably ready to get a move on with a PCB. 

6502 assembly code has enough routines to check ID's, erase EEPROMs (including 14V erase), and program with either 1-255ms programming pulses or 100us. 

I'm confident the hardware works, so now it's just a matter of committing traces to a PCB. Spending a lot of time getting the layout right, at the moment. 

I have a sponsorship lined up for PCBs and components, so the first 100 or so will be available cheap or really really cheap. 

Oh - and I also messed around with undoing my new 21V EPROM programming skills. Have a look if you haven't seen the video. 

Schematic has been updated and pushed to Github. Instructions added here.

Switching from shift registers to plain registers and muxing the data bus we should get a pretty good speed boost. Thanks to @Ken Yap for the upgrade idea!

I've yet to finish routing the PCB but the concept is ready for some actual testing. 

Time to stress test it on a breadboard! :)

The project started a few months ago as a forum thread on 6502.org

The project has taken a bit of shape, I've made the initial schematic and started designing the PCB. Before finishing the PCB the project needs a bit more time on the breadboard.

The idea is sound and deserves the work to be put in - even if it ends up being a bit slower than the commercial programmers. Cheap and easy to make is the goal!

Arduino seems like a reasonable platform to write some code for, but on the other hand it might be a lot of fun to make the #65uino self-replicating by letting it program it's own ROMs - especially since it has no problem reading out the whole ROM that's currently in the socket - but maybe thats more a log for that project :D

I'm aiming at 1/8th the price point of a commercial programmer(in parts) - we'll see if that's possible. 

Frustrated with the fact that you can easily get a bag full of W27C512 EEPROMs for single digit $'s, but you need a 70$ programmer I decided to make this!

It's supposed to plug into a host dev board, like a #65uino or other dev board and should program a wide range of electrically erasable (or just erasable) ROMs. 

I'm not sure how much I'll have ready for the 2023 Hackaday Prize, but it's still a good excuse to get some open hardware out the door!

P.S. Software not included for now