A DIY Upgrade for CFX-II

[Bill B]

One of the reasons that Martin and Dave developed the MFX was because the VGA output produced by the Parallax Propeller chip on the CFX-II was not always as stable as they would have liked.

At the same time as they were working on that, I was developing an alternate expansion board based around Raspberry Pi Picos. I was using a CFX-II as a development platform, and had developed a working Pico replacement for the Propeller. I was working on other aspects of the design. Martin and Dave finished first, making what I was doing irrelevant, so I abandoned the project.

A few weeks ago, a request on the Raspberry Pi forums for a VGA display with Z80 interface lead me to publish the code for the VGA display.

Since the code has been published it occured to me that some may be interested in upgrading their CFX-II. It requires making a daughter board to enable installing a Pico in place of the Propeller chip on the CFX-II. I have therefore published all the necessary details on GitHub.

There is no need to change the CFX-II ROM. The Pico reproduces all the functionality of the original Propeller. The only difference is that, owing to a lack of GPIO pins, the Pico does not decode the top two address lines. This will not make any difference unless you have additional non-standard hardware installed.

To be clear, I have no intention of making a production version of this upgrade.