hr@spica.astro.uiuc.edu (04/20/88)
I've got a question about connecting a MIDI interface to an Amiga. When I tried to attach an ECE interface to my 1000, the system hung after I told DMCS to activate the MIDI channel (serial port). As best as I can figure out, when the serial port is active, the Amiga is sensitive to voltages on pin 3 (receive). A constant 'high' voltage here will virtually halt the machine. In this case high is 1.7V. Any ideas as to what is the matter? Should the interface be sending a negative voltage when it is not transmitting data? Shouldn't the Amiga be able to ignore something like this? I'm guessing that the Amiga doesn't have a real UART and that one of its chips, Paula if I read it right, is trying to decode a character that isn't coming in. Another possibility is that DMCS is trying to use some weird magic that is failing. The serial port works when attached to either a modem or printer. Unfortunately, I can't flatly accuse the ECE interface. My Amiga's parallel port has been dead for awhile and since the 8250s are involved in so much, it is possible that the problem is there. Has anyone had experience with the ECE interface? Or is there a better one I should be trying? Thanks, Harold Ravlin hr@spica.astro.uicu.edu
mook@pnet02.cts.com (Ralph Stempel) (04/29/88)
There's nothing wrong with the ECE MIDI adapters in general. I would
suspect DMCS.
-RWS
UUCP: {hplabs!hp-sdd!crash, cadovax}!gryphon!pnet02!mook
INET: mook@pnet02.cts.comwtm@neoucom.UUCP (Bill Mayhew) (04/30/88)
In article <26800002@spica>, hr@spica.astro.uiuc.edu writes:
+
+ The serial port works when attached to either a modem or printer.
+
+ Unfortunately, I can't flatly accuse the ECE interface. My Amiga's
+ parallel port has been dead for awhile and since the 8250s are involved
+ in so much, it is possible that the problem is there. Has anyone had
+ experience with the ECE interface? Or is there a better one I should be
+
+ trying?
The ECE midi interface is noting more than a than a voltage to
current converter. It contains an opto isolator for MIDI in and a
transistor current driver for MIDI out. There are a couple of
resistors thrown in for proper biasing of the components. The ECE
interface does draw current from the power pin on the serial port;
this should be a problem only if there is a short in the ECE.
MIDI data is nothing more than 8 bit, no parity, 1 stop bit data at
a rate of 31,250 bits/sec. You can even pick that baud rate from
the WB 1.2 serial port preferences screen. If you use the original
ABasiC running under WB 1.2, you can even program your
synthesizer from ABasiC. Deluxe Music uses the indigenous
serial.device (apparently) for MIDI output.
If your 8250 is dead, it doesn't surprise me that the MIDI output
is not working .. but then the serial port should be dead too.
--Billfhwri%CONNCOLL.BITNET@cunyvm.cuny.edu (10/20/90)
1. Quite a few different MIDI interfaces are available, including AMAS, which
is also a sound digitizer.
2. All the MIDI interfaces plug in to the serial port, and most (I think)
use an optoisolator.
BTW, AMAZING published plans for a build-yer-own MIDI interface about
12-24 months ago...
--Rick Wrigley
fhwri@conncoll.bitnet