RC2018/04

I submitted an entry for the 2018 spring Retro Challenge which I alluded to in an earlier post. I've been neglecting posting my progress because I shot a bunch of video that I've "been meaning to edit" but I'm not sure how realistic that is, so here at least is a brief post that I am actually working on it and making progress (on the easy parts anyway).

RC2018/04 Pocket Computers!

My entry submission was kinda all over the place but vaguely unified around TRS-80 Pocket Computers. Apparently there is some controversy over whether these devices qualify as computers or are mearly programmable calculators. For the record, I fall very much in the computer camp.

I still have my childhood PC-3 which is the only original bit of technology from my youth that I kept until today. When I recently tried to fire it up I made a stupid mistake with the batteries (which I will detail in a later post) and thought it was dead. Before I had a chance to investigate, I stumbled on a really great eBay deal for a PC-3A with another cassette/printer interface, and a PC-4 for very cheap. On an impulse I bought it and only after it arrived did I realize my original PC-3 was mostly working after all. But both PC-3s had issues and both of the printer/cassette interfaces were basically dead. Naturally, the PC-4, which I initially had no interest in, and was just sorta a free bonus in my eBay purchase, was fully functional and worked great. As I played around with it a little, I came to appreciate it a lot more than I did as a kid but I realized that if I were to put any serious effort into programming it, I had no way to save any programs I wrote.

So my RetroChallenge was this:

• Refurb each PC-3 to fix minor issues.
• Refurb each PC-3 cassette/printer to make them functional at all
• Come up with a way to load/save files to th PC-4. Ideally loading and saving directly to a Raspberry Pi without needing to involve a cassette at all.

The first two parts were easy and are pretty much done (I actually cheated and refurbed one of the pocket computers so I could submit an entry to /r/retrobattlestations 4K Week Contest in late March. A more detailed write-up is coming. The 3rd part is mostly crazy-town. I don't really know what I'm doing but I'm going to try to do it anyway. I don't have a lot of hope for this but I'm going to see what I can do. This is the true "challenge" in my RetroChallenge.

TRS-80 Micro Color Computer MC-10

Growing up, I never had any interest in the TRS-80 MC-10. It was underpowered and had a terrible little keyboard compared to its bigger brother the CoCo. I would poke around on one now and then at Radio Shack but it never really had much interest to me. But since I've been lurking in lots of retrocomputing corners of the internet lately, I keep seeing them pop up and people are still doing interesting things with them. So when I saw a super cheap one on Craigslist, with the 16K RAM pack, cassette cable, and video cable included, I couldn't resist. Unfortunately, what wasn't included was the power supply.

MC-10 Rectifier

Normally a missing power supply would be no big deal. I've already got a few universal power adapters that I've been using for my Model 102, CCR-82, and PC-3 Printer. But the MC-10 is a weird little machine. It actually requires an 8V AC adapter, not DC. I did some googling and found posting in a forum that said DC would work fine, but the RS-232 port wouldn't work. I couldn't find anything to substantiate this claim but I did eventually look at the service manual and it does look like the circuitry should handle DC voltage just fine. It basically runs the AC through a recitifier to convert it to DC anyway. The service manual states that "a small amount of negative voltage is required to the RS-232 output op-amp" which you can see in the lower part of the circuit diagram above. "Vee" represents the negative voltage. In the full schematic, unless I'm missing something, the only place Vee is used is indeed an op-amp that makes up part of the RS-232 port. So in theory, as long as I don't use the RS-232 port, it should work okay on DC. . So I decided to give it try and, sure enough it boots up fine.

It works!

I do still plan to get the correct AC power supply at some point. My local Guitar Center has one that should work but that's considerably more than I paid for the MC-10 itself. A lot of people suggest the Atari 400/800 power supply is a good replacement so I may go with that, or I might try my luck on ebay but for now it's good enough to mess around with. It is also in pretty rough shape (this picture actually looks better than it does in person) so I think I'll take it apart and give it a good cleaning and try to retrobrite the case, which seems to be all the rage with the kids today.

BASIC 10Liners 2018 Results

The results for the Basic 10Liners 2018 constest have posted. My Long Jump game came in 8th place out of 24 entrants in the PUR-80 category. I'm pretty happy with the result. It's amazing what people are able to do in only 10 lines of BASIC code on some of these old machines.

Tigers '84

When I was a kid I had BASIC program that drew the Detroit Tigers logo on my TRS-80 Color Computer 2. Having recently aquired a CoCo2 once again, and with baseball starting back up, I was thinking about this program. I honestly couldn't quite remember if I made it myself or got it from a magazine. I used to take saran wrap and put it over a picture. I would then use a grease pencil to trace the picture and transfer the saran wrap to my computer screen to painstakingly recreate the picture using BASIC DRAW commands. But my memory of the Tigers logo was that it was probably too detailed for me to have done myself so I set about hunting through Rainbow Magazine archives and believe it or not I found it.

Here it is in all its 8-bit glory.

Model 102 Serial Terminal

Six years ago when I started this blog I was eagerly awaiting the release of the Raspberry Pi as well as the birth of my daughter. In fact they both arrived around the same time so I didn't have as much time to experiment with it as I would've liked. One of the things I never got around to doing was getting a serial console connection between my Pi and my Tandy Model 102. I ordered cheap little MAX232 kit and soldered it together but ran into some kind of trouble at the time. I don't remember what the issue was, and I don't think I even spent any time troubleshooting it, it just fell on the backburner until I finally dug it out again today.

In the intervening years this project has been done by plenty of others so I'm not going to bother detailing the steps, but I'm happy to have gotten it done nevertheless. I was really just looking for something to mess with while I wait for April so I can start on my RC2018/04 RetroChallenge entry. Watch for an upcoming blog post about my RetroChallenge project where I will detail exactly how much more I have bitten off more than I can chew. In the mean time, now that I have a working proof of concept here, my next step is to get it set up on my Raspberry Pi Zero W and put it into some type of compact case so I can have a convenient little box that runs TCPser to get some of my retro computers onto the internet.

BASIC 10Liners 2018

I recently heard about a contest to write a game in BASIC using only 10 lines. One of the requirements is that it be done on an 8-bit computer. I've been tinkering a lot with my old Tandy Model 102 so I thought this would be a fun project for it.

My original idea was to try to make a very simplified RPG-type game but I just couldn't fit it into 10 lines. Instead I switched gears and recreated a little game I had originally written on my TRS-80 PC-3 Pocket Computer back in the 1980s. My original PC-3 game was a javelin throwing game. Although I had a CoCo 2, my best friend had a Commodore 64 and we played a lot of Summer Games II which was my inspiration. Unlike the PC-4, the PC-3 didn't have any graphics characters built in and there were no bitmapped graphics either, so my program simply alternated printing X and Y as your player moved to sort of simulate running. Then when you hit a different key to throw your javelin the animation changed to moving a dash ( - ) across the sreen until it landed as a slash ( \ ) to look like a javelin stuck in the ground. It was the best I could do on a text-only single line display.

The source code for that game has long been lost so I had to remake it from scratch. I also made some changes from how I remember it, both for the contest rules, and to take advantage of the more powerful computer and larger screen. The Model 102 has two ASCII characters that look like stick figures in slightly different poses so I was able to use those instead of the X and Y of my original. I also changed the game to a long jump instead of javelin throw because with more than one line of text available on the Model 102 screen I could include a jump animation which looks better than my animated dash in the original. But the general gameplay is exactly the same. Basically you hit two keys on the keyboard as fast as possible until your player reaches a line on the screen then you hit another key to throw or jump. The distance you throw/jump is based on the speed you were hitting the keys and how close you were to the line.

There are some pretty amazing entries to the contest so I'm not expecting to place anywhere near the top, nevertheless, I'm pretty happy with the result given I only have 10 lines at 80 characters per line to work with.

The code is availabe on github https://github.com/ksbex/basic-longjump