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MIDIcar - Independent MIDI device for Atari XE

Posted: 15 April 2022, 06:57 - Fri
by pancio
I would like to present new device for Atari XE series which can play/record MIDI files on Atari 8-bit computer. Idea was taken from Mytek's SIO2MIDI ( but I decided to use CART/ECI port for communication with MIDI devices because in case I may use SIO independently for load/save data during MIDI working. Using CART/ECI provide possibility to use Atari as MIDI sequencer with direct access to FDD (SIO) and/or other mass storage device, for example with AVG CART (CART/ECI).

Project was made as Free Hardware under Creative Commons BY-NC-SA 4.0.

This is the next project created as part of the activities of PTODT (Polskie Towarzystwo Ochrony Dziedzictwa Technicznego, which means the Polish Society for the Protection of Technical Heritage), founded for the protection of technical heritage, especially in the field of informatics and computers.

MIDIcar is hardware which can nothing without software... best player I ever seen was written by PeBe:

This device is still under development. Please read whole information carefully. If you plan to do device by your own hand, please use newest revision as possible. Now it's 1.0.5 which is free of some minor issues on PCB.

Change log:
1.0 - first issue
1.0.1 - added polygons
1.0.2 - added correct polygons (connected to GND), Added good power distribution wiring.
1.0.3 - removed bad connection between /RST and /RTS
1.0.4 - added full address decoder for D5xx/D1xx (avoid issue with mixed decoders from Atari and MIDIcar)
1.0.5 - removed bad wiring between RD4 and RD5 on the PCB - now each cartridge can run with MIDIcar together.
1.0/1.0.1 PBI - first issue of MC PBI version.

- possibility to play external MIDI source like MIDI keyboard or synthesizer,
- MIDI IN/MIDI OUT LED indicators on board,
- serial communication with 31250 b/s, 125 kb/s or 2mb/s with PC (using e.g. FT232 dongle),
- fully transparent for other cartridges/interfaces (based on D1XX/D5XX address decoder),
- equipped with S2 DREAMBLASTER is ready to play (similar like SIO2MIDI,

Revision 1.0
First issue of MIDIcar v1.0 is dedicated for Atari XE series but I’ll prepare version for XL series as soon as possible,
MIDIcar 1.0 render
MIDIcar 1.0 render
MIDIcar-render.png (419.42 KiB) Viewed 36340 times
MIDIcar v.1.0 prototype
MIDIcar v.1.0 prototype
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The first whole MIDI file played on MIDIcar (PeBe's player):

According to ABBUC HSC 2022 event I'll share more details after competition...
Following topic:

Unfortunately, first release has two bugs on PCB layer:
1. bad crossed lines on audio channels output,
2. polygon was not connected to GND - so more noises might going to audio output

Revision 1.0.1
New revision (1.0.1) has been designed which eliminates the problem with audio and polygon connections:
MIDIcar 1.0.1-01
MIDIcar 1.0.1-01
MIDIcar1.0.1-01.jpeg (133.67 KiB) Viewed 35328 times
MIDIcar 1.0.1-02
MIDIcar 1.0.1-02
MIDIcar1.0.1-02.jpeg (113.55 KiB) Viewed 35328 times
MIDIcar 1.0.1-03
MIDIcar 1.0.1-03
MIDIcar1.0.1-03.jpeg (127.5 KiB) Viewed 35328 times
Parallel, my colleague Kkrys made prototype case for MIDIcar. It was first shown on Lost Party 2022 (Licheń Stary, Poland).
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MIDIcar-wood4.jpeg (168.5 KiB) Viewed 35328 times
The next photo shown that it's possible use MIDIcar with external memory expansion (512kb in case) so you don't need to modify stock Atari to enjoy most midi files :-)
midicar-prototype-case-socket.jpeg (163.71 KiB) Viewed 35328 times

But I was still missing something... MIDIcar was great at playing files loaded from the SIO device, but it didn't want to work with AVG, SIDE2 and my favorite IDEplus. And the worst thing is that I had no idea why this was happening... I ruled out conflicts on the address bus because the devices have different register addresses... I came to the conclusion that the problem is in... insufficient power supply due to the thickness of the traces on the PCB. This is how revision 1.0.3 was born.

Revision 1.0.2
Only better power distribution and signals was added...

Unfortunately, the problem has not gone away. I was able to play files from SIO and IDE2ECI without any problems. IDEplus and other devices were not cooperating... until finally, I found the (partial) cause... it turned out that I had mistakenly connected the /RTS (ready to send) signal of the MC6850 to the /RST (reset) signal, which caused the MC6850 to keep a permanent RESET on other devices. The fix is very easy... just leave the 5th pin of the MC6850 up and not connected. Of course, revision 1.0.3 will be made :-)

Now, IDEplus is working perfectly. SIDE2 and AVG (my favorite!) not yet but I'm still working on that.
MIDIcar_and_IDE+.jpg (756.35 KiB) Viewed 35325 times
Short test MIDcar under SpartaDosX and IDE+:

Revision 1.0.3 - 1.0.5
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Finally I found the bug which was responsible for not working with SIDE2 and AVGCART. it was short circuit between RD4 and RD5 signals... so, the solution is very easy, just cut one wiring between RD4 and RD5 pins on PCB ( close to CART slot):

MIDIcar - cart socket.png
MIDIcar - cart socket.png (349.32 KiB) Viewed 34107 times
MIDIcar wiring to cut.png
MIDIcar wiring to cut.png (132.47 KiB) Viewed 34107 times
Revision 1.0 PBI
Actually it's pretty the same as v1.0.4 but regarding of lack of internal decoder for D1/D5 page additional parts were placed on PCB. The same approach will be use in CART/ECI version (fully separately decoder for D1/D5).
MIDIcarPBI1.0.1-pcb-1.png (258.95 KiB) Viewed 3241 times
PBI version is equipped with additional power socket realized by standard DC-5 plug (+5V on center pin) - this is not needed if you have Atari 600XL or modified Atari 800XL (power mod on PBI) - pin 47 or 48 shall provide the power. You may configure how to power MC by dedicated jumpers on J9. Please use it with careful!
MCpbi-power.png (35.33 KiB) Viewed 3239 times
You may use MC-PBI with the same mass storage devices as MC-CART/ECI, It was tested with IDE2+, AVG and other...
MCpbi-1.jpeg (498.86 KiB) Viewed 3240 times
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MCpbi-2.jpeg (691.06 KiB) Viewed 3240 times

Re: MIDIcar - Independent MIDI device for Atari XE

Posted: 12 September 2022, 12:35 - Mon
by matej
I own 2x Dreamblaster so want buy 2x also will do enclosure and upload here STL. Also love it is cartridge upgrade as I use sio for SDrive:). Want use it for midi playback also for concert in future :).

Re: MIDIcar - Independent MIDI device for Atari XE

Posted: 12 September 2022, 13:09 - Mon
by pancio
Hi Matej,

Nice to hear that anyone in willing to use it :-) Unfortunately you should wait for a moment because Abbuc HW competition. When it will finished ( a couple of weeks ), a few devices will be available on PTODT market. If you are willing to build it by your own hand, the MIDIcar project will be available as as Free Hardware under Creative Commons BY-NC-SA 4.0.. The case was designed by my colleague KKrys and will be available as separately part.

Re: MIDIcar - Independent MIDI device for Atari XE

Posted: 13 September 2022, 08:58 - Tue
by matej
Yes I will wait and want buy 2x assembled also with cart and eci port but buy here as I live near Tatra mountains in Slovakia :).

Re: MIDIcar - Independent MIDI device for Atari XE

Posted: 13 November 2022, 19:10 - Sun
by pancio
I am pleased to inform you that MIDIcar was appreciated at the ABBUC competition in the second category. Thank you very much to all voters!

Full description, schematics and software will be available in first thread of this topic.