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Created by
 Western Graphics
Last modified
 13 March, 2004
 

Drumulator : External Computer Control

Overview The Drumulator can be completely controlled via an external computer by hooking up the computers RS232 port to the CLK/CASS IN jack on the Drumulator. This is a 9600 baud 8 bit serial interface. It was provided for "hobbyists" (read propellor heads !!) to hook their Apple computers up to the Drumulator. Remember this was in pre-MIDI days, when very few electronic instruments could inter work.

Entering a New Universe Press and hold the EXT CLK button, the display will read EC 01 (or something similar), then press RUN/STOP. The Drumulator will appear to die - all the LED's will go out. This is due to the Z80 micro processor being too slow to cope with scanning the front panel, and working with the incoming RS232 data. To get back out, press ENTER.

Pin Out The RS232 cable should be wired up as follows:-

RS232 Pin Name Drumulator Connection   1 Protective Ground No connection   2 Serial Output Clk/Cass IN   3 Serial Input No connection 4 Request To Send Connect to Clear to Send on the RS232 5 Clear to Send Connect to Request to Send on the RS232 6 Data Set Ready Connect to Data Terminal Ready 20 Data Terminal Ready Connect to Data Set Ready 7 Signal Ground Connect to shield ground

Data Format The external control data format is in 8-bit serial data at 9600 baud, with zero at -12V and 1 is +12V. Two stop bits are needed between each data byte to give the Z80 time to fire the sample. Each data byte instructs the Z80 to play one of the 12 drum samples at a certain volume. The sound is initiated during the stop bits. The most significant 4 bits control the level, and the least significant control select a drum sample, including the metronome click.

Call Marketing! The manual describing this feature surprisingly asks any user who has created an interesting program to call the marketing department !

The Graphic Rhythm Composer In fact you could buy a drum pattern sequencer for the Apple II/IIe to control the Drumulator. This software enables non-real time programming of measures and songs, with total dynamic control on a note by note basis. The GRC comes with a program diskette and an interface cable.  An Apple computer with at least 48 KB of memory is required (64 KB preferred), one disk drive and a two axis joystick (!) to control the cursor.

There are 4 modules in the GRC. A Measure Writer which enables notes to be entered on screen, complete with volume levels. It hold s this notes in segments. The Segment Writer links the measures together. The Song Writer links the segments into complete songs for storage on diskette. And finally, the Song Player actually plays back the programmed songs.

This is all pretty cool ....