Archive for May, 2013
This project had its start in a late 2009 discussion between Leif Bloomquist, a Canadian Commodore enthusiast and musician, and myself. Leif had been playing with a hand-built 6850-based VIC-20 MIDI cartridge designed off a 1980’s era Maplin “Electronics” article, and wondered if a production run could be arranged. I took a look at the design, and noted that the 6850 UART would be hard to source. I suggested some design changes to bring costs down, and plans were made to refine the design.
To further the design, I wired up a newer UART (16450-based) to a daughtercard that could plug into the 6850 socket on the original board. That allowed Leif to refine the software, and provide out the redesign. Once that was done and successful, we discussed a final production version. Changes included offering a built-in user-flashable ROM function.
That brings us up to late 2012. I purchased the parts for a completely new prototype board, but could not get it assembled by World of Commodore, so I brought the parts to the show and hired the assembly done.
Well, the assembly resource took longer than expected to finish the construction, but I did receive this same exact board mid-Feburary 2013. I fixed a few small design issues, only to discover the board expansion port was wired 100% backwards. Commodore, for reasons known to them only, named the pins on the VIC-20 expansion port in reverse from the industry standard. Since the prototype PCB pins were named according to the standard, every one would need modification.
I packaged up the board and sent it back to the assembler, but I must have messed up the address, as it did not arrive in a timely fashion. Since I had shipped it from the Post Office directly, I didn’t get tracking information, and thus had no idea of its location. After a few weeks, I resigned myself to the loss of the unit, and started gathering parts for a second unit to be shipped via trackable shipment to the assembler. As it turns out, the assembler and I were both planning to attend the 2013 Midwest Gaming Classic in WI, so I made plans to transfer a new set of parts during the show.
No sooner than the show ended and parts were transferred, the original package showed up at my office, undeliverable. I quickly saw the addressing issue, created a new trackable label with the correct address, and sent it on its way. Which brings us to last week, when the unit arrived, after the rewiring effort.
After all of that effort, I could now begin the potentially laborious task of debugging a “paper design”. I had designed the entire unit on paper, but had not previously proven out any of the elements on a breadboard. Though the original UART design was working on Leif’s PCB, the new design was marked different, owing to the additional decoding logic needed for the FLASH ROM. As such, it was almost a completely new design. I’m not sure if credit is deserved and who deserves it, but the UART and FLASH ROM read access worked out of the box. Bank selection for the FLASH ROM did not work, but that’s a minor issue.
And, we’re almost to the point of creating a VIC-20 MIDI production design.
I can’t claim a significant amount of creativity, but over the past few years, two folks have dropped off “VIC-Switch”-like devices in hopes that I could reverse engineer them. THese are devices used back in the day (typically in schools) to share a single disk drive or disk and printer with up to 8 computers. I long ago drew up schematics of the existing designs, but wanted to freshen up the solution instead of just creating a replica.
Well, as it goes, finding time takes time, but I decided to try my hand at a new design, and here is the current result. It’s not much at present, though I can enable/disable IEC ports, and “hold” the 64 from timing out the bus request. Yes, that’s an LCD there. I found a great price on them, and I think that’ll be in the final design. It’s only marginally cheaper than a 7 segment LED or two, and much more interactive then a few LEDs.
It’s been awhile since I developed firmware, and this gave me a chance to clean the cobwebs off my programming skills.
In the “another project that has been long in gestation” category comes a niche offering for those with Commodore SuperPET machines and a desire to run the OS/9 operating system. OS/9, a multi-tasking, multiuser, realtime OS with UNIX-like qualities, was popular in the 1980’s and ran on machines with the Motorola 6809. In addition to the small TRS80 Color Computer, the SuperPET includes a 6809, but the standard memory map of the SuperPET does not lend itself to OS/9 operation. That is where this little board comes in. Installation does not affect normal SuperPET operation, but extends it with OS/9 compatibility.
The SuperPET, a variant of the Commodore 8032 that included additional boards designed by the University of Waterloo, did not sell well, as far as I can tell, and limited (though not ultra-rare) numbers exist. Still, for those lucky enough to own one, OS/9 can truly turn the SP9000 (another name for the SuperPET) into the MicroMainFrame (another name for the SuperPET).
The project has been gestating since 2008 in some fashion. Late that year, TPUG member Golan Klinger asked if I could reproduce the SuperPET MMU board, which TPUG members created in 1985. for a possible club fundraising activity. I dutifully created a new layout of the design, and awaited next steps. Around the same time, Mike Naberezny (of 6502.org fame) started discussing the board, and we eventually compared notes. Over time, it became evident that TPUG was not going to pursue offering the unit for sale, and Mike performed a significant amount of legwork obtaining permission to replicate the software from Radisys (who purchased the OS/9 rights) and permission from TPUG leadership to offer the PCB. Thus, the majority of credit for this offering goes to Mike, who has a web site devoted to this impressive little board. I’ll put one in due time, but it won’t provide any more detail than Mike’s. I should also give a shout out to Steve Gray, who helped with information and PCB scans.
Currently, due to the low volumes, the unit will be available in kit form only for approximately $30.00. Thus, break out your soldering iron and a weekend of time to add this capability to your SuperPET!
Regrettably, I found out today that the upcoming C4 EXPO (which was going to be a all encompassing retro convention) has been cancelled for 2013. We last attending C4 EXPO in 2011 when it was held in The Drawbridge Inn in KY. In addition to the reasons given on the web site, I think the combination of the venue closure and the fact that the event was being managed by a single person contributed to the cancellation.
With the cancellation, CommVEX appears to be the next Commodore conference event. I’m not sure if RETRO Innovations can make the trip, but I am considering it. It would be nice to meet some of the west coast and southwest enthusiasts.