I did reverse engineer around 60% of the boot code of the DVI last year to work out how the Video and Floppy were used – most of it is very low level interface software for the FDC chip and some spaghetti code to control the graphics chip. Quite a lot of corners cut and some neat ways to deal with multiple interrupts on an Z80 is what I found - I thought I knew how to write Z80 ML!
Then ported the interface logic to a PIC 32MX (at least in essence) to produce VGA output at 40x26 or 80x26, with 3bit color if you wanted it. The drives use an SD Card with virtual Floppies to allow support for all the features found in disk basic. It runs all the diagnostics in the service manual and the user manual examples. I did extend it to provide color with esc sequences and some basic graphics – however it is very crude at the moment using print chr$(27) + code. The next step was to extend the disk basic with an overlay to take advantage of the enhanced capabilities. At that point I ran into a terminated apt lease and have spent time looking for somewhere to live. Everything is in boxes now. The board needs a respin to fix a power supply issue that will allow it to be properly powered from the model T. It can be powered from USB at the moment with a virtual serial terminal. It could be extended to mount the SD Card as a mass storage unit on a PC then write to or extract from the virtual floppy. As far as the model T is concerned it looks and runs like a DVI. It has been tested on the 100, 102 and 200. Oh and the cables do not need to be reversed :) There are quite a few sections incomplete that are not part of the regular DVI: WiFi, Analog inputs, Keyboard and Sound, all of which would require disk basic extensions to be used successfully or at least some low level BASIC/MK code. However I am no longer sure about these as the RS232 port might be a better solution for WiFi and the keyboard/sound are beyond the DVI spec. Anyway I will try to pick it up again once I have moved. I decided not to use the PI at the time because I wanted to be able to plug this into the Model T and use it as a disk drive without the need to use a power brick or anything beyond the T and power supply. If anyone has some good/interesting software to run on the DVI I would really appreciate access to test out the board. Thanks! From: M100 <[email protected]<mailto:[email protected]>> on behalf of George Rimakis <[email protected]<mailto:[email protected]>> Reply-To: <[email protected]<mailto:[email protected]>> Date: Wednesday, July 25, 2018 at 6:40 PM To: <[email protected]<mailto:[email protected]>> Subject: Re: [M100] Ask a silly question Has anyone managed to reverse engineer this DVI? That would be a neat project. ~George On Jul 25, 2018, at 9:30 PM, Randall Kindig <[email protected]<mailto:[email protected]>> wrote: Thanks, Brian, that’s very helpful. Randy On Jul 25, 2018, at 1:12 AM, Brian White <[email protected]<mailto:[email protected]>> wrote: Randy I never answered your last question about the Model 200 cable. It's these two items: https://www.amazon.com/gp/aw/d/B003PU1EVG/<https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.amazon.com%2Fgp%2Faw%2Fd%2FB003PU1EVG%2F&data=02%7C01%7C%7Cc7b3280776c84e21f30308d5f298c14b%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636681660240960767&sdata=J1WOI4CVLxSNjTvm7nSnaQ%2BxOaMjYgzK%2BLiM6VP3GTo%3D&reserved=0> https://www.amazon.com/Connector-Rainbow-Ribbon-Cable-1-6ft/dp/B00XP54YKE/<https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.amazon.com%2FConnector-Rainbow-Ribbon-Cable-1-6ft%2Fdp%2FB00XP54YKE%2F&data=02%7C01%7C%7Cc7b3280776c84e21f30308d5f298c14b%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636681660240960767&sdata=%2Fc%2BZE%2FCXrpMufrsdeRK52pv6m1UDFoazvIZH8DVu1Zk%3D&reserved=0> These are just representative examples pulled up quickly from amazon on my phone. You can get the same things lots of different places including ebay and digikey etc. That's it. You just stick the gender changer into one end and stick that end into the 102 or 200. For polarity assurance, just keep the cable flat all the way to the computer. That's it. No soldering, and the lack of polarity key on the computer end has an easy answer. And that cable works the same on both 102 and 200. I mean it can buch up or fold or loop any way it wants once it's connected, but just imagine both the DVI and the computer are sitting on a table, with the back of the computer facing the front of the DVI, and both boxes are sitting right-side up on their feet. From that starting position, the cable travels from under the front of the DVI to the computer without twisting or folding over. Whichever side of the cable is the bottom at the dvi, is also the bottom at the computer. If it was a grey cable instead of tha rainbow one, you could write "bottom" & "top" or "up" & "down" right on the cable at the computer end with a sharpie, and that would be enough for even an unsuspecting future owner to get it right safely. The DVI end is polarity keyed so you don't have to worry about that end. The only remaining annoyance with that cable is when you pull the cable out of the computer, the gender-changer pins are just as likely to stay in the computer as stay on the cable, and then they are a little difficult to get out of the computer because there is nothing to get a grip on. So you might want to use a tiny (tiny!) bit of super glue to keep the pins in the cable. Just enough to stick the two black plastic parts together, but try to avoid letting super glue wick and travel down into where the pins make contect inside the connector on the cable. Thanks to Mike Stein for the clue about the effect that kind of straight-through doulble-ended pin header ends up having on the pin mapping when you use one to butt two female idc plugs up to each other. It ends up having the same effect as the twists in the normal cable. -- bkw On Tue, Jul 24, 2018, 8:10 PM Randall Kindig <[email protected]<mailto:[email protected]>> wrote: I currently have 2. Until a few months ago I didn’t have any and had never seen a working unit. Now I have 2 great working units. I allows the M100/102 to display on a monitor rather than the small LCD. It also gives it one or 2 disk drives. They are great, if finicky. Randy On Jul 24, 2018, at 7:42 PM, Ken Gregg <[email protected]<mailto:[email protected]>> wrote: I see one of these units up for auction on ebay right now: https://www.ebay.com/itm/Radio-Shack-Tandy-TRS-80-model-100-disk-video-interface/223062580269<https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.ebay.com%2Fitm%2FRadio-Shack-Tandy-TRS-80-model-100-disk-video-interface%2F223062580269&data=02%7C01%7C%7Cc7b3280776c84e21f30308d5f298c14b%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636681660240960767&sdata=H0FP8mLEU2n0JoPylDBC2Kci%2BoTr5iDEhU441J3Nopg%3D&reserved=0> On 7/24/2018 12:25 PM, [email protected]<mailto:[email protected]> wrote: Oh! Well I've owned my M100 for years now and I had never seen the DVI. Are these rare? What advantages does this give over a stock M100 with a floppy drive? I gave a REX in mine, worth its weight in gold! Thanks for the replies guys, I still ashamed I didn't know what DVI was. Are these rare? Do many on the group have them? Sent from my iPad On 24 Jul 2018, at 8:12 pm, Kurt McCullum <[email protected]<mailto:[email protected]>> wrote: DVI = Disk Video Interface. It expanded the 100 or 200 with a 180k 5.25" disk drive and an external monitor. Attaches to the system bus and has it's own DOS. Kurt On Tue, Jul 24, 2018, at 12:07 PM, [email protected]<mailto:[email protected]> wrote: Perhaps I missed the memo, but I'm not familiar with DVI. Other than it being a firm video output. What is DVI in relation to the M100?
