MSX Cartridge, Cody Computer, Apple II...

Frontline Report:

Regarding the MSX cartridge, I'm still actively working on it. I'm currently implementing the YMODEM protocol on the internal processor of the Efinix Trion FPGA. The hardware and development software are now very stable. In advance, I've created a small interface card designed to be connected between the FPGA board and the MSX computer, with the goal of making the flash memory of the already-built expansion card for the FPGA board, available via a 'wired connection' on the MSX cartridge bus.

After successfully implementing a minimal 640*480 VGA interface on an Altera FPGA board, I must say that for the past few months, what seemed completely unfeasible to me—because it appeared too complicated—has actually turned out to be much simpler than I imagined.

And by the way, I am currently designing an expansion board—still for the Efinix FPGA board—featuring a 6502 processor, ROM, and RAM.

This time, the goal is to work on a hardware clone of the Apple II and an evolution of the Cody computer.

Regarding the Apple II, I had salvaged a machine in very poor condition from my former workplace. I had tried to get it working again and succeeded. But without knowledge and without the proper hardware environment, I couldn’t get it to do anything more than display its Basic prompt. Which was good, but still.

I then decided to build a clone based on a GitHub repository, the RETRO II : Retro II

But the development was unstable and unfinished. In fact, it never was completed. However, that experience allowed me to understand the Apple II hardware. I then thought to myself, “It shouldn’t be too complicated now” to revisit this study by replacing a large portion of the components connected to the processor inside an FPGA.

And with this expansion board, I also intend to take the Cody Computer concept a bit further. Because I find the work Frederick John Milens did absolutely fascinating. His machine resembles the Commodore 64, and above all, the documentation he provided is absolutely brilliant—it’s what makes the concept truly incredible. A highly relevant starting point for learning computer science—in the way I understand it, of course, which is, first and foremost, about the freedom to think and to create.

For more information about this machine, I invite you to visit the dedicated website: https://www.codycomputer.org

My personal take on this subject: having built this little machine, I feel I can allow myself to make an observation. In its current state, it requires the construction of a specific keyboard for input, as well as the use of an S-video to VGA or HDMI converter. This slightly diminishes its financial accessibility, since you have to add the cost of a custom keyboard plus the time to build it, and also add an external converter. Furthermore, it also reduces the machine's ease of use.

I imagine a 12 or 13-year-old who knows nothing about it, coming from a family where technical aspects are unfamiliar, wondering how to build and get such a machine running. For me, back in the day, I bought a Sharp PC-1500. An all-in-one where you just had to insert four batteries and read some simple technical documentation for a few hours to be able to start creating.

I would therefore like to add a USB port for connecting a standard keyboard, as well as replace the Propeller processor that manages, among other things, the video output of the original machine, with a system allowing direct connectivity to a monitor via an HDMI port.

I assume you understand where I'm going with this, given that I managed to create a 640*480 video card with VGA output, I'm thinking I might be able to push the concept to HDMI and graft it onto the Cody.

We'll see...

And then, I received another FPGA development board. Because I still want to make progress on the Drumulator reconstruction. I know the electronics of this machine well. All the development paths I've taken so far don't seem right to me. I think I want to have a functional machine in an FPGA to properly develop the rest of the hardware.

My last attempt at creating a Zilog-compatible CTC didn't work. Software simulation is a real hassle with the Efinix solution—at least, I haven't been able to get the hang of it. There is the option of using an external logic analyzer, but I'd probably use that more in the final development stage to validate signal timing.

On the other hand, now that I have mastered the internal processor of this Trion FPGA, I plan to use that processor to send test signals to the CTC. This will allow me to display all the information I want directly via the serial port. It's probably not the best solution for verifying a VHDL design, but well, for a bunch of reasons, it's still the approach I'm going to adopt.

I should clarify that I am not sponsored by Efinix. However, and despite a somewhat rocky start with this FPGA vendor's development tools, I must say that over the time, I've managed to get to grips with this development platform. I should say that the ease of integration of their RISC-V Sapphire processor core is, in my view, an undeniable plus. Well, in the past I thought I detected some potentially slightly troublesome features of the Trion FPGAs, particularly regarding clock signals, but I'm prepared for that. I can orient my designs appropriately. And, to top it all off, the development software doesn't require purchasing a license to enjoy the full potential of the IDE in terms of placement and routing and other optimizations.

It's a strategy I don't understand from the other vendors: charging for a license, sometimes an expensive one, to be able to fully use the target components? Well, one thing's for sure, if I do any work with FPGAs, it won't be with those folks. For them, it's all about whether it's profitable in the long run. For Altera, I think not, since the company hasn't existed for a few years now and was taken over by Intel, hum...