Modern In-Circuit Emulator For The 6809

July 19, 2024 by Alexander Rowsell 12 Comments

The Motorola 6809, released in 1978, was the follow-up to their 6800 from four years earlier. It’s a powerful little chip with many 16-bit features, although it’s an 8-bit micro at heart. Despite its great improvements over the 6800, and even technical superiority over the Z80 and 6502 (hardware multiply, for example!), it never reached the same levels of success that those chips did. However, there are still some famous systems, such as the TRS-80 Colour Computer, which utilized the chip and are still being hacked on today. [Ted] is clearly a fan of the 6809, as he used a Teensy 4.1 to create a cycle-exact, drop-in 6809 emulator!

A small interposer board rearranges the Teensy pinout to match the 6809, as well as translating voltage levels from 3.3V to 5V. With careful design, the Teensy matches the cycle diagrams in the Motorola datasheet precisely, and so should be able to run any applications written for the chip! A great test was booting Extended Colour BASIC for the TRS-80 CoCo 2 and running some test BASIC programs. Any issues with opcode decoding or timing would certainly be exposed while running an interpreted language like BASIC. After this successful test, it was time to let the Teensy’s ARM Cortex-M7 rip and see what it could do.

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Harmonic Table Keyboard Brings Old Idea Back To Life

June 17, 2024 by Bryan Cockfield 11 Comments

If you missed the introduction of the Axis-49 and Axis-64 keyboards by C-Thru Music, you’re definitely not alone. At the time it was a new musical instrument that was based on the harmonic table, but it launched during the Great Recession and due to its nontraditional nature and poor timing, the company went out of business. But the harmonic table layout has a number advantages for musicians over other keyboard layouts, so [Ben] has brought his own version of the unique instrument to life in his latest project.

Called the Midihex, the keyboard has a number of improvements over the version from C-Thru Music, most obviously its much larger 98 playable keys and five function keys. The keys themselves are similar to Cherry MX keys but which use Hall-effect sensors. This style of key allows the device to send continuous key position information to the host computer, and since this is a MIDI instrument, this capability allows it to support a MIDI protocol called MIDI Polyphonic Expression (MPE) which allows each note to be more finely controlled by the musician than a standard MIDI instrument. The PCB is powered by a Teensy 4.1 at the core.

For any musicians that haven’t tried out a harmonic table before, an instrument like this might be worth trying out. The layout provides easier chord and scale patterns, and for beginner musicians it can have a much shallower learning curve than other types of instruments. If you can’t find an original Axis-49 or Axis-64 anywhere to try out, though, we actually posted a teardown of one way back in 2009 when the company was still producing instruments.

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Backyard UFO Is Out Of This World

November 15, 2023 by Kristina Panos 11 Comments

Halloween may be over for another year, but UFOs in your yard are cool year-round. This one might take the cake. [frydom.john]’s excellent UFO is fully programmable and contains about 2000 addressable RGB LEDs, smoke, a laser-lit ramp, and of course, an alien crew.

Under the hood of the wooden frame, you’ll find a Teensy 4.1 running the blinkenlights. There’s also a hacked smoke machine, because what’s a UFO without smoke or fog emanating from underneath? There are six PC fans to blow it around and recycle it, and the ramp runs on a linear actuator.

[frydom.john]’s project notes (PDF), which they refer to as ‘scrappy/hacky’ are also available. We beg to differ a bit on the scrappy/hacky part; it’s 60 pages long and full of photos and diagrams and charts. Even so, it may not be enough for you to replicate this extraterrestrial vehicle, so [frydom.john] is open to questions. Be sure to check this thing out after the break.

Want to have your UFO lift off of the ground? It’s possible with the Coandă effect.

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Teensy Stands In For The Motorola 68k

October 31, 2023 by Bryan Cockfield 24 Comments

While it might not seem like it today, there was a time in the not-too-distant past where Motorola was the processor manufacturer. They made chips for everything, but the most popular was arguably the 68000 or 68k. It’s still has a considerable following today, largely among retrocomputing enthusiasts or those maintaining legacy hardware. For those wanting to dip their toes into this world, this Motorola 68000 emulator created by [Ted Fried] may be the thing needed to discover the magic of these once-ubiquitous chips.

The emulator itself runs on a Teensy 4.1, a 32-bit ARM microcontroller running at 600 MHz — giving it enough computing power to act as a cycle-accurate emulator not only for the 68000 CPU but also the local bus interface, in this case for a Mac 512K. This capability also makes it a drop-in replacement for the 68000 in these older Macs and the original hardware in these computers won’t notice much of a difference. A few tricks are needed to get it fully operational though, notably using a set of latches to make up for the fact that the Teensy doesn’t have the required number of output pins to interface one-to-one with the original hardware.

While the emulator may currently be able to replace the hardware and boot the computer, there is still ongoing development to get every part of the operating system up and working. The source code is available on the project’s GitHub page though so any updates made in the future can be found there. And if you have a Mac 128k and still haven’t upgraded to the 512k yet, grab one of these memory switching modules for the upgrade too.

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Apple III Slows Down To Smell The Roses

August 3, 2023 by Bryan Cockfield 7 Comments

The most collectible items in the realm of vintage computers often weren’t the most popular of their era. Quite the opposite, in fact. Generally the more desireable systems were market failures when they first launched, and are now sought out because of a newly-appreciated quirk or simply because the fact that they weren’t widely accepted means there’s fewer of them. One of the retro computers falling into this category is the Apple III, which had fundamental hardware issues upon launch leading to a large recall and its overall commercial failure. [Ted] is trying to bring one of these devices back to life, though, by slowing its clock speed down to a crawl.

The CPU in these machines was a Synertek 6502 running at 1.8 MHz. With a machine that wouldn’t boot, though, [Ted] replaced it with his own MCL65+, a purpose-built accelerator card based on the 600 MHz Teensy 4.1 microcontroller in order to debug the motherboard. The first problem was found in a ROM chip which prevented the computer loading anything from memory, but his solution wouldn’t work at the system’s higher clock speeds. To solve that problem [Ted] disabled the higher clock speed in hardware, restricting the system to 1 MHz and allowing it to finally boot.

So far there haven’t been any issues running the computer at the slower speed, and it also helps keep the computer cooler and hopefully running longer as well, since the system won’t get as hot or unstable. This isn’t [Ted]’s first retrocomputing rodeo, either. His MCL chips have been featured in plenty of other computers like this Apple II which can run at a much faster rate than the original hardware thanks to the help of the modern microcontroller.

Game Boy-Style Camera For Playdate

July 20, 2023 by Bryan Cockfield No comments

The Game Boy Camera, while perhaps not the most technologically advanced piece of equipment, left a huge mark on video game and electronics culture. The grayscale photographs are still highly prized, and there are an untold number of projects which interface with original hardware to download authentic Game Boy Camera pictures to modern computers. There are others that look to recreate the feel and style of these images, and the latest comes to us on a Game Boy-like platform as well, the Playdate.

[t0mg] is the creator of this project, utilizing a OV7670 camera module sending data to a Teensy 4.1 which interfaces with the Playdate via USB. The images recorded on the Playdate are 1-bit, slightly different than the 2-bit images the Game Boy Camera was capable of. The case of the camera also physically matches up well with the small console, using magnets to secure it to the device either in normal camera mode, in reverse for selfie mode, and can also support the console in “cover” mode as a way of storing the console to protect the screen. A companion application needs to run on the Playdate to get this all up and running, but with that and a battery plenty of retro-style images are ready to be captured.

All of the source for this project is available on the project’s GitHub page for anyone ready to experience some nostalgia or just experiment with a small camera like this. It’s a clean build that takes advantage of the Playdate’s open-source nature, through which we’ve seen the console turned into a typewriter and inspire other builds like this one-off handheld with a crank-style controller.

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Transform An Original Xbox Controller To A 360 Controller

June 7, 2023 by Bryan Cockfield 5 Comments

If you’re looking for a controller for your computer or mobile device, you could certainly do worse than one of the latest iterations of the Xbox pad. They might not be perfect, but they’re fairly well-made, not particularly expensive, use standard USB and Bluetooth interfaces, and even have decent support in the open-source community. So if you’re gaming on Linux or working on any other kind of retro gaming rig it’ll likely be plug-and-play.

This wasn’t the case with the first generation Xbox controller, though, and although its proprietary connector was actually using USB, the controller scheme wasn’t as open. This is [Tom]’s effort of upcycling his original Xbox controller to work indistinguishably from a stock Xbox 360 controller.

For those asking why anyone would want to do this, [Tom] is actually one of the few who enjoyed the original bulky Xbox “Duke” controller that released with the console in 2001. It wasn’t a popular choice in the larger gaming community and a year later Microsoft released a smaller version, but we all have our quirks. A Teensy 4.1 is attached to the end of the controller cable and acts as an intermediary to intercept the proprietary signalling coming from this controller and convert it into something usable. Since the controller doesn’t even show up as a standard USB HID device it took a little more sniffing of the protocol to decipher what was going on at all, but eventually some help was found within this other driver that gave [Tom] the clues he needed to get it working.

There were some other headaches to this project as well, especially since USB debugging USB connections while using USB isn’t exactly a streamlined process, but after a couple of breakthroughs the Teensy pass-through interface began working and [Tom] can use his controller of choice across multiple platforms now. If you’re looking to upgrade in other ways take a look at this build which seeks to recalibrate, rather than replace, an older Xbox controller experiencing drift on its analog control sticks.

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