Porting a Mac ROM SIMM programmer from AVR to ARM #Arm
Several months ago, Will from CayMac Vintage reached out to Doug Brown looking to resurrect his old Mac ROM SIMM programmer project. As a quick summary of that project, it provides a convenient way to program custom 64-pin ROM SIMM modules for vintage Macs from the late ’80s to early ’90s.
This got me thinking: how hard would it be to port the programmer to a new architecture? I was pretty sure I could drastically speed up programming time by using a faster processor without an I/O expander, especially if the data and address pins could be wired efficiently to full I/O ports that wouldn’t require special bit manipulation to read and write.
I mustered up enough motivation in my spare time to search for something a little newer that I might be able to port the firmware to. I looked on Digi-Key for microcontrollers that are 32-bit, can run at 5V, have at least 57 I/O pins, and can be a USB device. They also needed to be in stock.
The Nuvoton M258KE3AE appeared to be the winner and the board was redone with this controller and the software changed accordingly.
The new version of the programmer is known as the CayMac ROMmate-2 and is available to buy today.
Adafruit publishes a wide range of writing and video content, including interviews and reporting on the maker market and the wider technology world. Our standards page is intended as a guide to best practices that Adafruit uses, as well as an outline of the ethical standards Adafruit aspires to. While Adafruit is not an independent journalistic institution, Adafruit strives to be a fair, informative, and positive voice within the community – check it out here: adafruit.com/editorialstandards
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, TinyGO, or even use the Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for CircuitPython, MakeCode, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.
Have an amazing project to share? The Electronics Show and Tell is every Wednesday at 7pm ET! To join, head over to YouTube and check out the show’s live chat – we’ll post the link there.