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.
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