Monthly Archives: October 2020

Roger Taylor’s FPGA “Real CoCo” on MiSTer

A 1986 MacPlus on the FPGA MiSTer emulation hardware.

Earlier this year, I bought a MiSTer setup through Roger Taylor. MiSTer is an FPGA platform that can run recreations of consoles (Atari, Sega, Nintento, etc.), arcade games, and home computers (Apple, Commodore, etc.). Roger’s Matchbox CoCo FPGA project has been ported to it.

Here is the new Facebook group that covers all the various FPGA platforms Roger is working on:

https://www.facebook.com/groups/realcoco

Here is the MiSTer Wiki project page:

https://github.com/MiSTer-devel/Main_MiSTer/wiki

Here is Roger Taylor’s site:

I just unboxed mine and hooked it up the other night, and I am quite impressed. Being able to act as a virtualized hardware CoCo 3 as well as all the other machines is a game changer. Software emulators like MAME already let you do that, and I hope to do some comparisons between my Raspberry Pi emulator machine and this FPGA device.

And I still need to pick up a few more of the FPGA devices that can run the CoCo…

CoCo text screen can be changed in BASIC?

This writing is inspired by somethingI just saw in a YouTube video by 8-Bit Show and Tell:

In this video, Robin shows off an Easter egg found in the CoCo 2’s BASIC (the same one also found in the CoCo 1 since it was the same BASIC). He was wondering if there was any way to change the screen color (and I remember seeing someone ask this in the CoCo Facebook group but did not realize it was the Show and Tell guy). Australian programmer Nick Marantes gives him a “POKE 359,0:SCREEN 0,1” command to change the screen color… SCREEN can change the screen color? Surely I must have known this back then, but I had completely forgotten.

Thus, this article.

Nuclear Green CoCo Screen

The “nuclear green” screen of the Radio Shack TRS-80 Color Computer is certainly iconic. Black text on a green 32 column screen.

Disk Extended Color BASIC on the CoCo.

The Motorola MC6487 VDG chip contained a number of graphics modes, but only one text mode: 32×16 characters. The semigraphics modes supported up to 8 colors on the screen at the time, but text mode was limited to two colors: black on green. Well, except it was really a dark green on a light green. Here’s a zoomed in look, showing what color the text is compared to the black border:

CoCo “dark green” text on a nuclear green background with a black border.

I guess I sorta remembered this, because there was a way to invert the video to get light text on a dark background, and that background clearly wasn’t black:

Inverted text. Easy to do with a menu setting in the Xroar emulator.

I remember reading an article (probably in Rainbow Magazine) that showed how you could remove the VDG chip, pull up a pin, then plug it back in to the socket and get inverted video. I did that on my CoCo 1 since I thought that looked alot better (but not as good as if it was white on black like an Apple II or TRS-80 Model III).

The Xroar emulator has a menu option to toggle this inverted video.

But there was also a weird “pink” mode that I saw used in some early CoCo games. I recall reading a POKE or something that let you toggle it. You can also do that with the SCREEN command in Extended Color BASIC.

From the manual (page 96):

SCREEN type, color set displays the current graphics or text screen
type is 0 (text screen) or 1 (graphics screen)
color set is 0 or 1
Note: If type or color set is any positive number greater than 1, your computer uses 1.

Although not explained in the manual, you could select two color sets for the text mode. 0 was the normal dark green on nuclear green. 1 is the weird pink mode. But, when BASIC returns to the OK prompt, it resets the mode to 0, so you can’t use this to type things in (without a special POKE to bypass this reset). But, you can enter it in a program and then loop using a GOTO:

Alternate color set for text mode!

As soon as you hit BREAK and return to BASIC, the color resets to the green mode. The inverted mode looks like:

Inverted text color 1.

I don’t recall every using this mode, though I do recall at least trying it out with the POKE.

I do not know how to invert the video in software, but I expect there is a POKE to do that.

Anyway, there you go… alternate color sets for CoCo BASIC that you can access from BASIC using the SCREEN command.

More CoCo items (software, ROM-Paks, MC-10) for sale.

The great purge continues…

My CoCo 1/2/3 ROM-Paks:

https://www.ebay.com/itm/Radio-Shack-TRS-80-Color-Computer-CoCo-ROM-Paks/333745731777?hash=item4db4cbb8c1:g:fpcAAOSwjJFffRgC

Walt Disney cassette software (with boxes and everything):

https://www.ebay.com/itm/Walt-Disney-Radio-Shack-TRS-80-Color-Computer-CoCo-cassette-software-4-titles/333745728555?hash=item4db4cbac2b:g:x0QAAOSwqPBffRU~

Radio Ball (cassette game from Radio Shack):

https://www.ebay.com/itm/Radio-Shack-TRS-80-Color-Computer-Radio-Ball-game-on-cassette-w-packaging/333745757969?hash=item4db4cc1f11:g:tyYAAOSwCthffSKh

My MC-10 setup with memory expansion and Technical Service Manual:

https://www.ebay.com/itm/Radio-Shack-TRS-80-MC-10-computer-memory-expansion-and-software/333745738373?hash=item4db4cbd285:g:KaMAAOSwmZpffRu2

Radio Shack Appliance Light Controllers (Plug ‘n Power aka X-10):

https://www.ebay.com/itm/Radio-Shack-TRS-80-Color-Computer-Appliance-Light-Controller-NIB-X10-Plug-n/333745748407?hash=item4db4cbf9b7:g:wxgAAOSwZu9ffR6k

CoCo 3 “sealed in box” disk software: Where in the World is Carmen San Diego, Microsoft Flight Simulator II, and King’s Quest III:

https://www.ebay.com/itm/CoCo-3-Kings-Quest-III-Carmen-San-Diego-Flight-Simulator-II-NIB/333745755468?hash=item4db4cc154c:g:0bwAAOSwRKRffSGj

CoCo graphics tablet, video digitizer and speech recognition hardware for sale!

The great purge has begun! I have to downsize to about 50% of my current stuff, so it’s time to sell off all the CoCo gear I have that I will no longer be actively using.

First on the list is a Radio Shack X-PAD Graphics Tablet. This is still in the original box, with the original manual and template, as well as the plastic bags that came covering the pak and tablet! It’s as complete as it gets.

https://www.ebay.com/itm/333744740596

Next is the E.A.R.S. speech recognition system that was sold by Speech Systems. Yep, voice recognition on the CoCo! It could recognize 64 voice patterns, if I recall, and used simple BASIC commands to listen and match the voices. It needed a headset that was special so I don’t have a way to test it.

https://www.ebay.com/itm/333744732187

Then there is the Micro Works DS-68B video digitizer! Yep, the one with software that Tim Jenison (later of Newtek and the Video Toaster for Amiga) programmed! It works! But the label has come lose and will need to be “restored” with some glue.

https://www.ebay.com/itm/333744721237

Lastly, the Rulaford Research CoCo MIDI Pak with options — two switches that toggle the ports to THRU and OUT and such. I got this direct from Cecil Houk himself, and used it for years. I no longer have anything with MIDI, so … away it goes.

https://www.ebay.com/itm/333744735920

Please bid and help me raise some much needed money, and downsize at the same time. Thanks!