Sunday, 19 May 2013

The State of Play

I actually started work on this project about 6 weeks ago. But it does have to compete for time with Real Life, so it's going to be somewhat of a drawn-out process.

The easiest way to explain where it's at is just to say that I've completed the "interesting" parts of the schematics. In other words the FPGA, all the memory devices, the ARM, the video IC's and the bulk of the connectors have been done. What's missing on the schematics include the power supplies, analogue video amplifiers (for JAMMA), the analogue audio circuit, and all the really boring bits like de-coupling capacitors and sundry miscellaneous protection components on some of the I/O.

As a result, all the major IC's and the AES/MVS connectors have been selected, based primarily on their availability from Digikey. The flash devices are dirt cheap, and for simplicity I've gone with the same device for all ROM's. The SRAM can be used as either 8-bit or 16-bit mode, which is a bonus. The HDMI chip incorporates audio, is readily available and looks relatively simple to use. The video DAC I've used on another design. I've also used the STM32F2xx family before.

I should mention here that I've managed to coerce a few colleagues into assisting with the design; my business partner is handling the power supplies and related boring bits, and another colleague is designing the analogue audio & video circuits.

As for layout, I've just started to collect footprints for the various components. Fortunately a good selection of the larger IC's have footprint libraries already available. I've done the AES/MVS connectors myself. I'm envisaging the board to look similar to a 1-slot MVS board; JAMMA connector on the front, cartridge connectors at the back, additional audio/video connectors on one side, and controller connectors on the other. At least that's the plan...

I suspect there's a few more weeks, if not months, of schematic capture and review remaining before we can start layout proper. To some degree I'm at the mercy of my colleagues as well, but we're also pretty busy at work atm, let-alone the other aspects of our respective lives. Layout is going to be a massive job, and I'm inclined to sub it out else I'm afraid it'll languish for many months in the too-hard basket. Of course, that's added expense...

In the mean-time, I might re-visit the HDL I wrote a few years ago and see if that has suffered any bit-rot. And of course, I'll need to spend a bit of time on my AES console once the first of my carts turns up - you know, for science!

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