MIDI/80

A MIDI Sound & Interface Card for the TRS-80 Model 1, III, and 4

Hardware & Firmware: Michael Wessel

Z80 Wizardry and TRS-80 Zmac Assembler Advisor: George Phillips

Beta Testers: Jürgen Wich (Model 1 Version), Joel Hilliard (Model III / 4 Version)

License: GPL 3

News

February 2026

Joel Hilliard aka DOWNPOLY released his new album, TETHER_:

Unlike his previous album where MIDI/80 and TRACKER were mainly used for drums (it couldn't do more back then!), he is now increasingly utilizing it for full backing tracks on his songs (for bass, melodies, chords, ...). By now, TRACKER is a full-fledged 6channel multi-timbral MIDI sequencer (organized into 26 pages which can be flexibly sequenced in song mode). More MIDI channels can be realized by synchronizing multiple TRACKERs running on dedicated TRS-80s, via the parallel port sync cable (see below). Joel is tpyically using 2 to 3 synchronized TRACKERS for his work. See below for more details.

Please support his work on Spotify if you like his songs on YouTube (also see here.)

October 2025

• Playback of extremely large MIDI files is now possible - "Karn Evil 9" by "Emerson Lake & Palmer" requires 15 16 KB segments. This requires a Gotek floppy emulator and some tricky 80-track disk images. Thanks to folks on the TRS-80 Discord for helping me with these. There is a new playback program BIGLOAD/CMD which loads /MID files with alphabetic suffixes (A - Z). Here are demo disks for the Model 1 (and .HFE) and the Model III (and .HFE). An X-MEM/80 is required; use the 16KB (X-MEM/80) mode. Enjoy - here is a YT video.

Source code of BIGLOAD/ASM.

To create your own very large MIDI song playback disk, just use these disk images as blueprints and exchange the SONGA/MID ... SONGO/MID files (you can go up to SONGZ/MID). The MIDI converter still creates SONG0/BIN to SONG<n>/BIN segments, so you need to rename them to be loaded with BIGLOAD/CMD.

September 2025

• Playback of large MIDI files is now possible: X-MEM/80 makes this possible. X-MEM/80 is a new 512 KB (paged) RAM extensions for the Model 1 and Model III that is "plug & play", i.e., requires no hardware modifications. Here is a demo video (playback of a very large MIDI file). The details and software as well as disk images can be found here, on the X-MEM/80 repo.

• Joel Hilliard aka DOWNPOLY presented MIDI/80 and its software (Tracker, MIDORG, MIDI Playback etc.) at Tandy Assembly 2025 in Springfield, Ohio. Great talk, Joel! Also, a DOWNPOLY Live Performance is scheduled as well.

August 2025

• I demoed MIDI/80 and the MIDI tracker playing a DOWNPOLY track at this year's Vintage Computer Festival West in Mountain View. MIDI/80 was primarily driven by TRS-IO++, but I also had one connected to my Model III. Also on display was Talker/80. Here is a YouTube video showing my table.

June 2025

• Thanks to Peter Kirn from the "cdm (create digital music)" blog for writing a comprehensive article about MIDI/80, Downpoly's great music, and the software that we wrote for it: "Radio Shack’s TRS-80 now has polyphonic MIDI and a tracker"

• Thanks to Hackaday (Levin Day) for covering MIDI/80 on the front page::

April 2025

As suggested by a recent customer, David, I have made a little Tracker 1.98 tutorial, good enough for first steps / getting your feet wet.

DOWNPOLY is using multiple Tracker 1.98 by now, synchronized over the parallel port cable - check out his YouTube video!

March 2025

It is now possible to synchronize multiple Trackers running on different machines:

Here is a demo video.

The latest version of the Tracker, Version 1.96 (tracker5/cmd on the disk images) is now sending an external clock signal over the parallel port, on Data 0. Another TRS-80 Tracker can then be configured to latch on to this external clock by setting it into external clock mode with the ' key. The receiving TRS-80 Tracker is called the secondary, and the clock generating Tracker the primary. Enable the external clock mode on the secondary with the ' key. Then start playback as usual, in pattern (P) or song playback mode (!). As usual, you can always refer to the help page for key bindings (H). The secondary Tracker is frozen until it starts receiving the clock signal from the primary Tracker via the parallel port cable; the tempo setting of the secondary will be disregarded, as the tempo is determined by the external clock from the primary. External clock can be en- and disabled using the ' at any time; also, with the exception of the tempo setting, recording and all the other Tracker operations and settings work identical as if the internal clock was used.

External clock:

Internal clock:

To make the cable, simply connect the Centronic ports of the two machines as follows: GND to GND (e.g., Centronics pin 2; note that there are multiple options for GND), and the Data 0 output (Centronics pin 3) of the primary to the BUSY input (Centronics pin 21) of the secondary. And easy way to construct the cable is to cut two TRS-80 printer cables in half, and solder the wires together:

March 2025

Since March 21st I am proud owner of a Behringer Wave! I always admired the PPG Wave created back in the day in 1981 by Wolfgang Palm, inventor of Wave Table Synthesis, in my birth-town Hamburg, Germany. It's utterly amazing what he achieved and accomplished with so little - he didn't even have a C-compiler for software development. All the firmware / software for his synths was programmed in bare-metal 6809 assembly.

Thanks to Behringer for cloning / re-creating the PPG Wave, and for making it affordable! So everybody can experience the magic of this legendary iconic influential synth now, for an extremely fair price. I couldn't be more happy with it - the build quality is excellent (enclosure is solid sheet metal!), the keyboard surprisingly good for the price, and it even has aftertouch. The sound is excellent as well, and it really reproduces the original sound quite faithfully as far as I can tell. I believe the recreated Curtis filter chip plays a key role here.

I am super happy with the Behringer Wave, as it allows me to make music that sounds like Tangerine Dream and Depeche Mode from the early 1980s. This video features my first steps with it, using Tracker 1.95 in song mode.

February 2025

Thanks to Jürgen Wich, who created a new batch tool that makes bulk creation of MIDI song disks a breeze! Check out his awesome new MIDI Conversion Tools for MIDI/80 and TRS-80! His software tool suite can be found here.

Thanks much, Jürgen, great work!

January 2025

Jürgen Wich has uploaded a demo video showcasing the MIDI/80 MIDI playback capabilities with his Model 1 - cool stuff!

https://youtu.be/vjVPdRUbgE4

December 2024

• Cool TRS-80 Orchestra + MIDI/80 music performance by Joel Hilliard on the Model 4 and 4p (using STORCH/CMD and TRACKER/CMD for S2 drums).

https://www.youtube.com/watch?v=8xH_k91aPCo

November 2024

• Jürgen Wich (the "Homecomputerguy.de") was one of the beta testers for the Model 1 version, and has just uploaded his review - thanks, Jürgen!

https://homecomputerguy.de/en/2024/11/24/midi-80-trashy-spits-out-new-sounds/

• MIDI/80 is featured project on Hackaday.com!

• This Github goes online. Firmware, Gerbers, and sources released to the public.
• The first beta tests were a success! Both Jürgen and Joel have successfully used MIDI/80 with their TRS-80s.

October 2024

MatrixSynth posted about MIDI/80 - thanks!

About

MIDI/80 is a MIDI Sound & MIDI Interface card for the TRS-80 Model 1, III, and 4.

TRS-80 Model with Expansion Interface, MIDI/80, and Orchestra 85 replica:

TRS-80 Model III with MIDI/80 and FreHD HD emulator connected to the MIDI/80 expansion port pass-through edge connector:

MIDI/80 on a TRS-80 Model 4 with TRS-IO++:

Features

MIDI/80 offers:

• A powerful and sonically impressive, versatile General MIDI (GM) sound & MIDI interface card for the TRS-80 Model 1, III, and 4.

  GM sound is either produced by a Waveblaster-compatible soundmodule that plugs onto MIDI/80's Waveblaster header, or via a GM expander (such as the Roland Sound Canvas SC-55 or Roland MT-32) conntected to MIDI/80's MIDI OUT DIN socket. MIDI data can be sent to either or both of these devices. Both the Waveblaster module as well as the MIDI DIN sockets are optional, but in order to act as a soundcard, either of these options need to be present.

• Standard MIDI IN & MIDI OUT DIN sockets (optional) turn your TRS-80 into a powerful MIDI processor. You can connect a standard MIDI keyboard to the MIDI IN DIN socket, and record MIDI messages with the TRS-80 into memory. MIDI messages can also be played back from the TRS-80 memory. The MIDI data recording is fast enough to allow for the real-time recording of entire multi-track complex GM songs, i.e., from a PC playing back a .MID MIDI file via MIDIBAR.

• Stand-alone mode: equipped with a Waveblaster sound module, MIDI/80 is also a "headless" GM expander, not unlike the Roland Sound Canvas SC-55 (without display though). The MIDI/80 firmware provides a standalone MIDI mode - this mode is enabled by putting DIP Switch 3 into "ON" position. No TRS-80 is required in this standalone mode, only a 5 V power supply and an external amplifier.

• Compatible with popular TRS-80 standard expansions: Model 1 Expansion Interface, FreHD, Orchestra soundcards, Talker/80, etc.

• OpenSource BluePill firmware, Gerbers, and TRS-80 software available here.

• TRS-80 software available, and more under development: Drum Pattern Tracker, MIDI Recorder, TRS-80 Synthesizer, etc.

• DIY friendly: only thru-hole and off-the-shelf components are used.

• Inexpensive: MIDI/80 can be assembled for ~35 USD. The most significant cost factor is the Waveblaster module, if required. If you already own an external MIDI expander such as the Roland Sound Canvas or similar, no Waveblaster plugin module is required.

Technical Details

• Requires standard 5V "wall wart" power supply; 1 to 2 Amps, center positive.

• Requires an external stereo amplifier to be connected to the standard 3.5 mm stereo audio jack.

• Powerful BluePill STM32F103C8T6 Microcontroller clocked at 75 MHz (ARM Cortex-M3).

• Compatible with all Waveblaster soundcards from Serdashop that don't require a 12 V supply.

  

• Uses off-the-shelf Adafruit MIDI breakout module. The MIDI sockets are optional, as is the Waveblaster sound module.

• Five activity LEDs that indicate read and write activity on the TRS-80 IO bus related to MIDI/80, as well as incoming and outgoing MIDI message activity. Useful for debugging MIDI problems.

• Full TRS-80 expansion port pass-through. MIDI/80 is a "good citizen on the bus" and compatible with Talker/80, FreHD, Orchestra 85 and 90, etc.

• Reset button on the BluePill microcontroller.

Demo Videos

You can get a better understanding of MIDI/80's capabilities and features by watching some of these YouTube demo videos:

• "MIDORG/CMD" - MIDI/80 TRS-80 synthesizer demo
• Playback of some complex GM songs from Model III RAM
• "TRACKER/CMD" - MIDI/80 drum tracker demo
• "MIDORCM/CMD" - George Phillips' MIDI/80 + Orchestra organ program
• "RECPLAY/CMD" - Realtime recording and playback of very complex MIDI data with the Model III
• "RECPLAY/CMD" - Realtime recording and playback of very complex MIDI data with the Model 1
• MIDI/80 and external MIDI expanders - GM song playback with the Roland MT-32 connected to MIDI OUT DIN socket

Overview & Usage

Connect the IDC box header at the bottom to your TRS-80 Model.

Use the pass-through edge connector to connect other hardware (e.g., the Model 1 Expansion Interface, or a FreHD) to MIDI/80.

MIDI/80 requires a dedicated external 5V standard center-positive "wall wart" power supply (1A is sufficient).

It is recommended to power-on MIDI/80 before the other TRS-80 equipment.

Installation Notes

• For the Model 1, the 40 pin ribbon cables should be as short as possible. If the Model 1 Expansion Interface (EI) is being used, then MIDI/80 should be connected directly to the Model 1, and not to the EI expansion port edge connector (front-left side edge connector at the EI). See this picture for a proper setup:

• For the Model III, it is convenient to place MIDI/80 directly on top of the machine. The expansion port cable runs along the rear side of the console, to the top. Connect additional external hardware such as your FreHD directly to MIDI/80's pass-through expansion port edge connector, as shown in this picture:

Moreover, it is important that expansion cards connected to MIDI/80's pass-through connector use a fully connected 50pin ribbon cable! This is necessary in order to avoid crosstalk, as every other strand of the 50pin ribbon cable is GND. It was found that the 50pin card edge connector of an Orchestra 90 replica board using only a 40pin ribbon cable (hence, 10 pins of the 50pin card edge connector were left non-connected to MIDI/80's pass-through connector, as Orchestra 90 doesn't require these signals for operations) resulted in MIDI/80 databus read failures. Switching to a fully connected 50pin ribbon cable fully resolved the issue.

• For the Model 4, the above notes for the Model III apply. In addition the Model 4 must be run in SYSTEM (SLOW) mode, as MIDI/80 only supports the 2 MHz max CPU speed from the Model III; so the Model 4 must be operated in Model III mode if MIDI/80 is to be used.

Operating MIDI/80

MIDI/80 is equipped with a RESET button

a 4-position DIP switch, and 5 activity / status LEDs:

Please note the following:

1. The RESET button is on the BluePill microcontroller.

   Use the RESET button at any time; the TRS-80 is not affected by a reset. A push to the RESET button will also reset the on-board Waveblaster module and clear (turn off) any potentially stuck notes.

2. The five activity & status LEDs indicate the following:

   • Upon RESET / Power On, the LEDs are tested for function and then briefly display the current DIP switch setting.

     This is useful for testing proper operation of the DIP switch (i.e., that all switches are working). The default DIP SWITCH setting is ON-ON-OFF-ON.

   • At runtime, the LEDs have the following function:

     • DATA-IN: Data is received from the TRS-80 via IO port 8.
     • MIDI-IN: MIDI data is received via the MIDI IN DIN socket.
     • DATA-OUT: Data is sent from the BluePill microcontroller to the TRS-80. The repective IO ports are 8 and 9 (see below).
     • S2-OUT: MIDI data is sent from the BluePill microcontroller to the internal Waveblaster connector.
     • MIDI-OUT: MIDI data is sent from the BluePill microcontroller over the MIDI OUT DIN socket.

3. The four DIP switches are used for selecting the operating mode of MIDI/80.

   From left to right, the switches 1 to 4 have the following functions (note that there are also small labels under the buttons on the PCB silkscreen). In the following, x is either M1 (for the Model 1 version), or M3 (for the Model III, Model 4 version):

   • x --> S2: Determines if data received over IO port 8 from the TSR-80 is forwarded to the internal Waveblaster plugin module. Default setting is on.

   • x --> OUT: Determines if data received over IO port 8 from the TSR-80 is forwarded to the MIDI OUT DIN socket. Default setting is on.

   • IN --> S2: MIDI/80 standalone GM expander mode. Determines if data received over the MIDI IN DIN socket is automatically forwarded to the Waveblaster plugin module. Default setting is off.

     This is a function of the MIDI/80 firmware, i.e., the BluePill is doing this autonomously, without TRS-80 involvement. You only need a 5V power supply and an external amplifier, and can use MIDI/80 as a very capabale GM expander module for your Waveblaster sound module with this mode.

   • IN --> OUT: Determines if data received over the MIDI IN DIN socket is automatically forwarded to the MIDI OUT DIN socket.

     This, again, is a function of the MIDI/80 firmware, i.e., the BluePill is doing this autonomously, without TRS-80 involvement. It basically implements a MIDI THRU function; note that this function is not exclusive to the MIDI OUT socket. The TRS-80 can also still send out data over it.

Note: After a change to the DIP switch, a RESET is required in order for the change to become effective (use the RESET button on the BluePill).

Operating System Notes

On all systems, LDOS 5.3.1 is the default operating system for which the software is developed. Model 4 users must configure their machine via SYSTEM (SLOW) for MIDI/80.

The MIDI/80 programming examples in BASIC are written in LBASIC (LDOS BASIC) and are not guaranteed to work with the other BASIC dialects.

All other programs are written in Z80 assembly using George Phillips' Zmac assembler and trs80gp emulator as development toolchain.

Important Notes for FreHD Users

If you are using MIDI/80 and the provided example programs with a FreHD harddisk emulator, then the following important information applies to you. Else, if you boot LDOS from Gotek / disk drive, you can ignore this section.

Thanks to Matthew Boytim for figuring out the following mystery: the MIDI/80 playback programs (e.g., CANYON/CMD demo song) run about ~32 % faster if started and run from a FreHD LDOS, compared to an LDOS booted from disk / Gotek.

The reason is the keyboard driver; to ensure equal playback speed, please enter RESET *KI before starting the playback program (e.g., CANYON/CMD) if a FreHD LDOS is used!

Moreover, the FreHD ROM / image also loads certain drivers into high memory regions, which would be overwritten by large demo songs such as TOCCATA/CMD. This song causes a SYS ERROR if executed from FreHD LDOS. Hence, it only runs from Gotek / floppy disk LDOS.

Theory of Operation

MIDI/80 implements a FIFO queue with a capacity of 256 bytes for buffering incoming MIDI messages which are received over the MIDI IN DIN socket. The status of this buffer can be queried by reading from IO port 9 - a 1 indicates MIDI bytes are queued for retrieval from the buffer, and a 0 indicates an empty buffer. MIDI bytes can then be retrieved from the FIFO by reading from IO port 8.

If the standalone mode is turned on, i.e., DIP switch 3 is set to on, then all MIDI data bytes received over MIDI IN are also automatically forwarded to the Waveblaster module.

If MIDI THRU is turned on, i.e., DIP switch 4 is set to on, then MIDI data bytes received over MIDI IN are also automatically forwarded to the MIDI OUT DIN socket.

MIDI data bytes received by MIDI/80 from the TRS-80 via port 8 will not be buffered, but, depending on the settings of DIP switches 1 and 2, immediately be forwarded to either the Waveblaster pluging module, and/or the MIDI OUT DIN socket, or both or none. Both routes can be turned on or off individually, and independendly of each other.

MIDI/80 is implemented using 4 ISR (Interrupt Service Routines). There is a pair of ISRs for handling reads and write to TRS-80 IO port 8, and one ISR for handling IO port 9 reads. Another ISR is responsible for putting MIDI bytes received via the MIDI IN socket into the FIFO buffer. The MIDI ISR has priority over the ISRs serving the TRS-80 IO - the Z80 CPU may be put into WAIT state in case these events happen concurrently.

The BluePill does the heavy lifting, but requires some help from three additional glue logic support chips in order to meet the strict bus timing constraints of the TRS-80 with a "not quite fast enough" microcontroller such as the BluePill @ 72 MHz:

• A GAL16V8 is primarily used as an address decoder for IO ports 8 and 9. It notifies the BluePill and triggers the appropriate ISRs. It also implements some glue logic for driving the other two support chips.
• A 74LS244 is used to decouple TRS-80 databus read requests from the BluePill databus.
• A 74LS374 is used to decouple TRS-80 databus write requests from the BluePill databus.

In combination, the 74LS244 and 74LS374 greatly relax the timing constraints on the BluePill ISRs. Without them, the design would not work.

MIDI/80 Software for the TRS-80

Note that many of these programs are demonstrated on the YouTube MIDI/80 channel (see above).

There is a set of MIDI/80 song disks containing GM songs for playback, simply for listening pleasure. These also serve as standalone demos. See below for info on how to make your own songs for MIDI/80. The software is under development, and there might be frequent or infrequent updates in the future.

The programs on the MIDI80.DSK, MIDI80_DSK.HFE Model III disk images are:

• ALF/CMD, TOCCATA/CMD: MIDI Demo songs; playback of complex GM data from TRS-80 RAM.

  

• MIDORG/CMD: Turns your TRS-80 into a full-blown polyphonic multitimbral MIDI keyboard. You can play the Waveblaster (S2) or an externally connected GM expander with your TRS-80 keyboard. This is joint-work with George Phillips, as the program uses his keyboard scanning and self-modifying key handler code.

  

• TRACKER/CMD, TREACKER1/CMD: A drum pattern sequencer for your TRS-80. TRACKER1/CMD allows realtime tracking / recording over the MIDI drum channel (10) from a connected MIDI keyboard / synthesizer (via MIDI IN).

  

  

• RECPLAY/CMD: A MIDI data recorder and MIDI data playback device. You can record the incoming MIDI IN data stream into TRS-80 RAM, and play it back from there. This program is fast enough to support real-time recording of entire complex GM songs, as demonstrated in [this demo]. In a future version, it will be possible to save (resp. load) the recorded MIDI data (GM songs) to (resp. from) disk.

  

• DRUMS/CMD: A simple program demonstrating how to program MIDI/80 with Z80 assembly language. Use your TRS-80 keyboard to play the MIDI drum channel (channel 10). The ASCII codes of the keys are mapped to instrument numbers.

  

• MIDIMON/BAS: A simple MIDI monitor. Prints MIDI data bytes to the screen. Useful for debugging MIDI issues. Also demonstrates how to query the FIFO buffer from LBASIC.

  

• MIDITRU/BAS: A simple MIDI SOFT THRU implementation in LBASIC. Simply forwards any MIDI byte received via MIDI IN DIN socket to either the Waveblaster, to the external MIDI OUT DIN socket, both, or neither, depending on the DIP switch settings (1 and 2). Also demonstates how to query the FIFO buffer from LBASIC, and how to send MIDI data from BASIC.

• BASDRUM/BAS: The LBASIC version of the simple drum program above, but unlike DRUMS/CMD, it's much more laggy (it's BASIC!), and it only supports keys 0 to 9. Unlike DRUMS/CMD, these keys are mapped to sensible MIDI drum notes on channel 10 (e.g., 0 is mapped to the bass drum, etc.)

• NOTES/BAS: Simple LBASIC program that demonstrates how to send MIDI NOTE ON and MIDI NOTE OFF messages. Plays all 127 notes of the Waveblaster, and/or external MIDI module, depending on the DIP switch settings (1 and 2).

There is also some software that was written by George Phillips that requires an Orchestra 85 (Model 1) or Orchestra 90 (Model III, Model 4) soundcard:

• MIDORCM/CMD: With this program you can play your Orchestra (85, 90) interactively via a MIDI keyboard connected to MIDI/80's MIDI IN socket. It is monophonic. The program is somewhat "picky" as it requires a proper MIDI NOTE OFF message to turn of a note. Note that some MIDI keyboards choose to send a MIDI NOTE ON message with velocity (= "volume") 0 instead. Also, key roll-over is not implemented yet.

• STORCH/CMD: Allows you to play the Orchestra (85, 90) soundcard with your TRS-80 keyboard. The program can generate different wave forms (sine, square, saw, triangle), and utilizes both the left and the right channel of the Orchestra - each channel can be played via a dedicated row of keys (one octave) from your TRS-80 keyboard! Even the channel volumes can be changed.

  

Creating Your Own Songs for MIDI/80 Playback

Use the .MID to .BIN file converter. The converter is written
in Python, and provided as a Windows executable here.

There are a few MIDI files here you can start with.

The converter will convert a MIDI .MID file into a set of 16 KB .BIN fragments. A fully expanded Model 1 allows you to fit about ~43 KBs of song data into memory.

In order to create your own MYSONG/CMD file, proceed as follows.

1. Edit the CANYON.ASM Zmac assembly program as a blueprint. First, make a copy, give it a reasonable name, e.g., MYSONG.ASM.

   Then, change the line

   `title2		defb  '    CANYON.MID', ENTER` 
   

   by replacing CANYON.MID with your song title, e.g., MYSONG.MID

2. Include as many of the the generated .BIN fragments of your song as possible by replacing the following lines

   incbin "./canyon0.BIN"
   incbin "./canyon1.BIN"
   incbin "./canyon2.BIN"      
   

   with the proper file names for your song:

   incbin "./mysong0.BIN"
   incbin "./mysong1.BIN"
   ...
   

3. Next, download and install Zmac as well as trs80gp, and assemble the program from the command line as follows:

   zmac$ ./zmac maysong.asm 
   

   Then, test the generated CMD / program in the trs80gp emulator:

   zmac$ ./trs80gp -ld zout/mysong.cmd
   

   Note that the playback program display RAM region occupied by the binary song data:

   

   The song data must stay below $FFFF; if the value of the display end address is smaller than the start address, then the memory "wrapped around" and the song data did not fit. LDOS will not allow loading the program in this case (as it would need to overwrite the ROM, which is impossible).

Note: You can use TRSTOOLS to add the generated MYSONG.CMD to a DSK image, and convert this DSK image into HFE format using HxC.

MIDI/80 Programming

Have a look at the LBASIC demo programs on the DSK images, and the DRUMS/CMD assembly program.

MIDI/80 Hardware

This section provides all necessary files and information for a DIY build of MIDI/80. Costs are in the ~35 USD range (without a Waveblaster module; add another ~40 USD for the S2, but prices vary).

Schematics

Model 1 Version (PDF)

Model III / 4 Version (PDF)

Bill of Material (BOM)

• 40 (Model 1) or 50 (Model III & 4) pin IDC box header
• 40 or 50 pin ribbon cable
• 40 or 50 pin card edge connector
• 3.5 mm stereo jack
• BluePill microcontroller (and ability to program / flash it, e.g., using a ST-Link V2 BluePill programming cable)
• GAL16V8 + DIP socket (and ability to program it, e.g., using TL-866 MiniPro Programmer)
• 74LS244 + DIP socket
• 74LS374 + DIP socket
• 5 (5mm) LEDs of your liking and matching current limiting resitors (1 or 2 kOhm)
• 4-position DIP switch
• C1 in the schematics (and on the PCB) is actually not a capacitor, but a cable / wire bridge
• L Type Mounting Feet
• Standard 5V DV power plug jack (5.5x2.1mm socket)
• Standard 5V "wall wart" external power supply (center positive)
• Dual-row breakable pin headers
• Optional: Waveblaster module
• Optional: Adafruit MIDI Feather and Single Row Straight Female Header Socket Connector for Arduino

PCB Gerbers

The PCB Gerbers are contained in Zip archives and can directly be send-off to major PCB manufacturers (PCBWay, Seeed, OshPark, JLCPCB):

• Model 1 Version:

• Model III / 4 Version:

Assembly Notes

Note the proper IDC header orientation, i.e., the position of the "notch" differs between Model 1 and Model III / 4 version!

• On the Model 1 version, the 40pin IDC box header notch faces towards the edge connector.
• On the Model III / 4 version, the 50pin IDC box header notch faces away from the edge connector.

Firmware

Here are the required firmware files for the GAL16V8 and BluePill microcontroller.

Model 1 Version:

• GAL16V8 JED firmware file
• GAL16V8 PLD sources

Model III / 4 Version:

• GAL16V8 JED firmware file
• GAL16V8 PLD sources

Installation of the STM32 FreRTOS and GCC development toolchain is explained in Warren Gay's book "Beginning STM32 - Developing with FreRTOS, libopencm3 and GCC", which I can recommend.

With the development toolchain installed and configured correctly, and an ST-Link V2 USB programmer
connected, the BluePill firmware can be compiled and uploaded onto the BluePill simply by executing

make clean
make
make flash 

from the command line. I am using Linux for this, even though CYGWIN is mentioned as a possibilty in the aforementioned book.

Acknowledgements

• Warren Gay for his book "Beginning STM32 - Developing with FreRTOS, libopencm3 and GCC" which provided the starting point and basis for this work.

• George Phillips

• Jürgen Wich

• Joel Hilliard