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...
But 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.