When we first looked at [Anders Nielsen’s] EEPROM programmer project, it was nice but needed some software and manual intervention and had some limitations on the parts you could program. But through the magic of Open-Source collaboration, revision 2 of the project overcomes all of these limitations and—as you can see in the video below—looks very polished.

If you recall, the programmer is in a “shield” format that can plug into an Arduino or — if you prefer a retrocomputer — a 6502uno. Along with hardware improvements from the community, [Henrik Olsson] wrote Python software to handle the programming (see the second video below).

The biggest change in the new version is that you don’t have to configure the voltages with jumpers anymore. This was required because different devices draw power on different pins, but a clever two-transistor circuit lets the software handle it. There is still one jumper for switching between 32-pin and 28-pin EEPROMs. The extra transistors added four cents to the total price, although if you buy the kit from [Anders], it is still $9, just like before.

Skimming the database, we don’t see any Microcontrollers (MPUs). However, it looks like the device should be able to program flash MPUs, too.

We covered the first edition of this project, and we were impressed even then. We do hope people will add MPUs and other devices like PALs to the project over time.

As we all know, when developing software for any platform or simply hacking a bit of code to probe how something works, the ability to deploy code rapidly is a huge help. [Martin Donlon], aka [wickerwaka], is well known in retro gaming and arcade hardware reverse engineering circles and had the usual issues figuring out how an arcade CPU board worked while developing a MiSTer core. Some interesting ASICs needed quite a bit of poking, and changing the contents of socketed ERPOMs is a labour-intensive process. The solution was PicoROM, a nicely designed ROM emulator in a handy DIP-32 form factor.

As the title suggests, PicoROM is based on the Raspberry Pi RP2040. It emulates an 8-bit ROM up to 2MBits in size with speeds up to 100ns. Since it uses the RP2040, USB connectivity is simple, enabling rapid uploading of new images to one (or more) PicoROMs in mere seconds. A vertically orientated USB-C connector allows multiple PicoROMs to be cabled to the host without interfering with neighbouring hardware. The firmware running on core 1 passes data from the internal 264K SRAM, using the PIO block as a bus interface to the target. A neat firmware feature is the addition of a mechanism to use a ROM region as a bidirectional control channel, which the software running on the target can use to communicate back to the host computer. This allows remote triggering of actions and the reporting of responses. Responses which may not be physically observable externally. [Martin] is using this feature extensively to help probe the functionality of some special function chips on the target boards, which is still a slow process but helped massively by reducing that critical software iteration time. The PCB was designed with KiCAD. The project files for which can be found here.

This isn’t the first time we’ve seen the RP2040 used for ROM emulation; here’s a pile of wires that does the same job. It just isn’t as pretty. Of course, if you really must use EPROMs, then you could give this sweet programmer a look over.