I feel your pain. Your MDX-15 was designed around ten years ago and
uses traditional RS-232C serial communication. Modern computers and
their USB serial ports demand that you do one of two things:
Install a RS-232C serial port option card in your computer
Purchase a trustworthy USB>RS-232C serial converter that also is
compatible with your Vista operating system.
Your local computer dealer should be able to supply and fit (1) for
you. Then you need to
a) ensure you configure your software to use that serial port, and
b) set the serial settings to 9600, 8, 1, none, hardware handshake,
c) be sure to use a genuine Roland hardware handshake serial cable
from the port to your MDX-15.
If you instead choose (2) you may have a bit more research to do.
The makers and sellers of USB>RS-232C serial converters fall into 3
d) those who genuinely support hardware handshake protocol, and
e) those who think they support all protocols but didn’t actually
check before advertising, and
f) those who know perfectly well their converter product does NOT
support hardware handshaking but tell all the necessary lies to get
your money and smile as you hand it over.
It’s imperative to select a converter from category (d). But they
are not finished with you! Some converters only do hardware
handshaking with certain operating systems.
This is becoming very long and boring, so feel free to contact me
through my website - I will not be selling you anything, just helping
you, being a former Engineering Technology Manager for Roland DG (in
Australia) who escaped nearly 5 years back, physically with only
minor scrapes and bruises!
Summary: Take Option (1) !!! and feel free to correspond with me for
free help - gratis. There is an inquiry form on EVERY page of my
website, to get you in contact.
Happier New Year with your MDX-15, which has many years of
productive life left in it!