[sdiy] New to list - and DSP development

[Magnus Danielson]

From: Phil Harbison <alvitar at comcast.net>
Subject: Re: [sdiy] New to list - and DSP development
Date: Sun, 12 Dec 2004 12:37:40 -0500
Message-ID: <41BC81E4.4080201 at comcast.net>

Phil,

> Magnus Danielson wrote:
> > A MacIntosh MIDI interface is really a double interface,
> > since you need to signal-level convert in two steps rather
> > than one if you go straigh from a UART.
> 
> What additional step is required? The old Macs used RS-422
> which is differential with 0-5V swing as opposed to RS-232
> which is single-ended with -N/+N swing (where N should be
> around 12V but is as little as 5V for some of the RS-232
> drivers that generate their own power supply from +5VDC).
> If you plan to have a long cable between the Mac and the
> MIDI convertor, you'll want to use an RS-422 receiver at
> the MIDI end; otherwise, just ignore the TD- half of the
> RS-422 pair and convert the TD+ signal to current loop. I
> can post a crude schematic if anyone is interested.

I used the propper RS-422/423 convertion chips, which was what I was indicating
as the second interface.

Cheers,
Magnus