djc@wlcrjs.UUCP (David J. Carpenter) (12/07/84)
Has anyone any specifications for the MIDI interface found on many synthesizers? All I know is: It is serial It sends messages about events such as: key pressed/released program changed pedal pressed, etc. It uses a 5-pin DIN connector I am interested in interfacing to a CP/M computer. Thanks, -- David Carpenter ...!ihnp4!wlcrjs!djc
RMS.G.HNIJ%MIT-OZ@MIT-MC.ARPA (12/09/84)
Write to: Internatonal MIDI Association 8426 Vine Valley Drive Sun Valley CA 91352 (phone = 213-768-7448) Ask for the MIDI specifications. I have started to interface it to a CP/M computer. Haven't had time to get it working yet. The actual hardware interface is easy -- an opto-isolater, a few diodes and resistors. You need 5vdc out, running at 31.25 kilobaud (strange number, eh?). Same for input. @hnij@ John Labovitz hnij%oz@mit-mc.arpa -------
ron@BRL-TGR.ARPA (12/09/84)
Turns out the MIDI interface users group (or whatever) went bust. Some aquaintance of mine claims to have the spec, but I haven't been able to worm it out of him. From looking at the schematics and information provided with the Roland IBM-PC interface, we came up with the following conclusions: Each midi plug is a uni-directional twisted pair line running at 36 Kb (or maybe it was only 19.2). The data is serial eight bit bytes. One bit is a tag to indicate whether this is the first byte of multibyte messages or not. They list the "unit independent" codes in the Roland manual. Each synth typicallly has three MIDI plugs, in, out, and thru. In receives commands and interprets them. Thru is just an out- going copy of in for chaining. Out contains commands from the keyboard and controls of this synthesizer. There are 16 channels which are just "addresses" so you can talk to the synthesizers individually. Most computer interfaces usually have an option to echo there in signals on the out plug so that you can put them in the loop between your favorite keyboard and the rest of they synths. The keyboard only instruments like the Roland MDK also echo the in on the out since they really don't do anything with the in signals. As far as interfaces go, I know of three. They are the ROLAND, the Garfield, and the Passport. The passport is the cheapest (around $150) and the hardware is not intelligent. All the work is done bythe host software. I've seen this one on the apple. It works adequately, but they intend to come out with better editing programs. I've not seen the Garfield in use so I can't comment. The Roland (which costs about $500, once you get everything) has a little external processor box. This box, when in smart mode, records the incoming notes, timestamps them, and buffers them going into the machine. It's a little more eloquent. You can bypass the buffering if you want. It comes with a little eight track recording program and two prerecorded songs. The program is fairly nice, but hitting reset seems to send crud out on the midi and this sometimes zaps my DX-7. The two songs provided (LISZT which seems to be Liebestraum and BJ (a jazz piece, possibly Bob James?) are really neat demos. I'd personally go with the Roland, except I may end up with the passport or in addition. The DX-PRO software which is an intelligent screen oriented set up of DX-7 voices and includes 800 additional voices, only runs on the passport and an apple. I hear the guy who wrote it, quit before doing any IBM versions. -Ron
mangoe@umcp-cs.UUCP (Charley Wingate) (12/09/84)
Please post the response or mail a copy to:
Charley Wingate {seismo|allegra|rglvax}!umcp-cs!mangoejwg@lanierrnd.UUCP (Joe Guthridge) (12/11/84)
I have a copy of the spec. If you would like a copy, send me an envelope with postage. (Sorry - too long to type in.) It runs at 31.25K Baud - a strange number until you realize that most UARTs require a 16X clock, which in this case would be 500kHz. Joe Guthridge 576 Westover Dr. Atlanta, GA 30305 -- Joe Guthridge ..!akgua!lanierrnd!jwg