Blast from the Past: Tandy 1000TL/2

A little over two years ago I was finishing building the XTIDE Adapter with the Dangerous Prototypes free PCB. Using their Bus Pirate I was able to flash the CPULD, but you need a computer to flash the BIOS. Upon pulling my Tandy 1000TL/2 (my first computer were I learned the basis of everything I do today) out of the closet, I realized after trying a standard keyboard that it requires an XT keyboard. Drat! When my wife and I moved first moved to Monterey, I had gotten rid of a bunch of stuff. I couldn't remember if the Tandy keyboard was one of them. I know I got rid of the monitor(s) and dot matrix printer. Either way, I still haven't found it.

Once in a while I would think about this project and looked up ways to create an adapter from AT to XT. It's cheaper and it takes up less space then getting a $$$ XT clicky keyboard on eBay. More recently I had found some decently priced ones on eBay but never pulled the trigger. 

Then after our trip to the Portland Mini Maker Faire and staying/talking to my best friend, it sparked my motivation to finish this project. We had visited a computer recycling place in search of a keyboard. They thought they had one, but not all 5pin din keyboards from yesteryear are XT. So looking on eBay can be tough as well. The best bet are ones that obviously have a switch.

It was a debate of either a keyboard or making an adapter. None of the adapters people have made use USB. All are PS/2 to XT/DIN using a MSP430 or PIC. Finally, I found a clean keyboard at an okay price and had it shipped. I'm still thinking the adapter would be cool to make though. 

The night before I bought the keyboard, I decided to give the adapter a try just as a proof of concept. Using an MBED Arch Pro (which uses the LPC1768 that has USB OTG) and a working USBHost library, I was able to sort of get something working. I ported the code from the vintage forums to MBED. I still need to learn the XT protocol better since it doesn't quite work. I have to remove the PS/2 code and replace it with USB. 

But I ran into a slight problem. I tried to power the Arch Pro from the keyboard 5V+ and the next time I checked my pinout I wasn't getting 5V+ anymore. Oops. I had read there is a one time fuse on the 5V rail. Sure enough after carefully taking it apart I spotted and tested the bad fuse. Argh.

So now what? Over the next day or so I decided to get the keyboard but still get the parts to test making an adapter. I decided to upgrade the single pop fuse with a polyfuse. I have to kinda guess what the max is though. I remember reading something about 300mA. I got a 250mA one so I should be safe. I am deathly afraid of damaging anything. Bad enough I am going to have to solder to a 25 year old motherboard. It's like doing dismantling a bomb, you only get one chance! Remember this is the computer that got me and probably many others where we are today. I even have an 8-Bit VGA ISA Video Card. Good thing too.

Here are some pictures of the current setup. I used the Arch Pro and then the USB Tester to inject 5V+. At least till I get the fuse in later this week. 

This keyboard seems to pull a steady 70-71mA. I just have to be careful how much power the adapter I make uses. I am probably going to use a STM32, cheaper than LPC1768 and Arduino Due that have USB OTG. Just have to do some more tests before I design a PCB. There are lots of uC's with USB OTG but I don't want to spend a bunch of time getting it to work. Rather I'll use something where a library already exists.

Yay! Finally, I can now flash the BIOS to the XTIDE adapter and start copying files. Of course after all of this, I realized there isn't that much data so I simply could have used a bunch of floppies to get it over to my "normal" computer. Since AOL killed their member websites, I was hoping there was a copy of my old AOL members website. Now that would've been sweet.