Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!sdd.hp.com!spool.mu.edu!munnari.oz.au!metro!tplrd!markb From: markb@tplrd.tpl.oz.au (Mark Bower) Newsgroups: comp.music Subject: Re: RS-232 to MIDI Message-ID: <1991May15.231906.4819@tplrd.tpl.oz.au> Date: 15 May 91 23:19:06 GMT References: <2679@fornax.UUCP> Organization: Telectronics Pacing Systems Lines: 73 In article Frank2.Simon@arbi.informatik.uni-oldenburg.de (Frank 'Biber' Simon) writes: >troy@fornax.UUCP (Troy Brooks) writes: > >>I'm trying to find an RS-232 to MIDI interface to connect to the >>.. >>(MPU - 401 ?) don't use RS-232 because the baud rate is too slow on >>PCs. (9600 baud). So, if I can't find one, I'll have to build one, >>... > >It isn't possible to build a RS-232 to MIDI-Interface, because >the baud rate is too slow (it's up to 19 200 Baud). The only way >is to specify the RS-232-Interface. The only different between >RS-232 Interface and MIDI is the very high baud rate (31.250 Baud) >and the optical split to disconnect the Keyboard of the Computer. You can use a baud rate convertor - i've seen an RS-232 to midi convertor box that stores RS-232 output (e.g. any baud rate from 9600 to 19.2 K bps - use it on your ancient CP/M machine - if you can program it!) convert the RS-232 levels to TTL and then buffers them with a MIDI standard approved optocoupler for connection to MIDI devices. the name of the firm that makes this box > >So there are only two things to do: > >1) A new Quartz to get the 31.250 Baud >2) Optodisconnectors to make two circuits. > >To 1) >In the RS-232 Interface there is a UART 8250 doing his job. >He has got some frequency-divider in it. 31.250 Baud is for >example to get with a quartz of 4 Mhz and a divide rate of >128 (because 4 M/128=31250). Not all RS-232 ports use the 8250 - that's PC (mostly) specific - also, most RS-232 cards in PC's use 8250 UARTS that have a maximum driver clock rate of 2 Mhz - so be aware of this if you are doing it. (You just use a different baud rate divisor value) > >To 2) >In the MIDI-Specifikation is written to use Optodisconnectors. >Because of the high baud-rate you can't take every one, but >there are some working with this rate. > >In the german journal C't (computer-Technik) of Januar this Year >there's written a articel to build a MIDI-Interface of a RS-232. >The C't suggest to build a luxury MIDI-Interface which can be >switched (via software) between MIDI and RS-232 mode). >The electric-parts you need aren't very expensive. It isn't also >hard to build this Interface. > >For more details mail me >-- >FRONT242FRONT242FRONT242FRONT242FRONT242FRONT242FRONT242FRONT242FRONT242FRONT ^^^^^^ Good tast in music. Hope this info helps someone Cheers, Mark /\ ------------------------------------------------------------|/ \ /----------- Mark F. Bower. (markb@tplrd.tpl.oz.au) | \/ Telectronics Pacing Systems | "beep blop beep woop" R & D | - any techno song at the moment 7 Sirius Rd. | Lane Cove 2066 | -------------------------------------------------------------------------------