LONDON, UK: MIDI utilities specialist Kenton is proud to announce availability of the GPMX-16 MIDI to GPI and GPI to MIDI converter —
the latest addition to its growing family of compact and sturdy MIDI
utility boxes, that allows any GPI-equipped device to ‘talk’ MIDI — as
of June 13...
first, a little background: commonly called GPI (General Purpose
Interface), IEEE-488 is a short-range digital communications bus
specification that dates back to the late Sixties for use with automated
test equipment. While still used for that purpose today, it has
unsurprisingly since been the subject of several revisions. As a
standard contact closure format used in broadcast-level post-production,
it allows computer-based editing equipment to synchronously ‘start’ at
the same time, for example. Now any such equipment can easily be
integrated into commonplace MIDI (Musical Instrument Digital Interface)
setups thanks to Kenton’s communicative GPMX-16 MIDI to GPI and GPI to MIDI converter.
As implied by its (full) name, the bi-directional GPMX-16 MIDI to GPI and GPI to MIDI converter comes
complete with 16 GPI inputs and 16 GPI outputs arranged across four
standard 9-pin D-sub connectors — sockets for inputs (labelled GPI 1-8 IN and GPI 9-16 IN) and plugs for outputs (labelled GPI 1-8 OUT and GPI 9-16 OUT).
When inputting a manual switch signal into a digital circuit the signal
needs to be debounced so a single press does not appear as multiple
presses; in the case of the GPMX-16,
the debounce value for all switch inputs can be set between one to 100
milliseconds (defaulting to 10 milliseconds) to ensure that this does
not happen. The GPI inputs themselves are arranged with internal
pull-ups, so shorting an input to ground will send the appropriate MIDI
ON message and releasing the short to ground will send a MIDI OFF
message (unless disabled). The GPI outputs are floating and can switch
up to 50V at 100mA of resistive load. They can also be controlled by
MIDI ON and OFF messages or provide a pulse of settable length in
response to just MIDI ON messages (by default). Each block of eight GPI
inputs and outputs can be assigned a MIDI starting number, and
subsequent inputs and outputs follow on consecutive note numbers
(defaulting to 36-43 for the first block and 44-51 for the second). MIDI
channels can be set independently for the GPI inputs and outputs
(defaulting to transmitting on Channel 1 and receiving on Channel 2).
As well as allowing users to control the GPI outputs using MIDI, the MIDI IN socket also allows several GPMX-16 MIDI to GPI and GPI to MIDI converter boxes
to be daisy-chained together (without any limit to the number of units
that can be daisy- chained as the data is regenerated rather than being
merely copied). Any data received at the MIDI IN socket is merged with any new data generated from the GPI inputs and everything is subsequently sent to the two MIDI outputs (MIDI OUT and MIDI OUT 2)
carrying identical information. A second MIDI output has been
thoughtfully provided so that data can be sent to a backup computer
system at the same time as supplying a primary one.
In a nutshell, then, the GPMX-16 MIDI to GPI and GPI to MIDI converter can
receive and output MIDI messages as Note, Controller (CC), or Program
Change data when operating in normal operating mode. However, it also
has a number of additional parameters that can be edited and stored when
it is put into edit mode (using a screwdriver or pen to press the
recessed front panel-positioned EDIT button and adjacent INC, DEC, and SELECT buttons
to receive and display different types of MIDI messages). Such settings
are stored in EEPROM (Electrically Erasable Programmable Read-Only
Memory) for future use.
As if that is not enough to be getting on with in its own right, the GPMX-16 MIDI to GPI and GPI to MIDI converter handily
has a built-in MIDI analyser — allowing users to see what types of MIDI
messages are being transmitted by their master keyboard or sequencer,
for instance, doubling up an already well-specified MIDI utility box
that is indispensable to GPI- equipped device owners to also act as a
useful diagnostic tool.