[sdiy] New to list - and DSP development

[Phil Harbison]

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.