Sequencer for Maplin 3800 Synthesiser
During the late 1970's I built a Maplin 3800 Synthesiser and for the past 30 odd years it has lay unused in my loft, now I have resurrected and repaired (quite) a few faults. At that time I also built a sequencer to control the systhesiser key presses as it had the capability for some basic external control. This is pre-midi, the keyboard generates a binary code for each note which with a couple of controls are brought out to the back panel in the form of a 9 pin computer interface - 8 bits, six for the notes, one for 'Gate' or 'Key Down' and the other to enable the interface.
The Raspberry Pi with its GPIO is an ideal device to use to as sequencer, with this script and the interface it is easy to produce some reasonable sequencies. Sequencers of the day usually could play around 24 notes with all notes having the same time between them and to loop at any note. With v1.0 of the script I have emulated this but have increased it to 32 notes, v2.0 script allows for individual times between notes - a bit more flexible. At present the sequencer works with the binary code for each note, an obvious improvement would be to input the notes as C, C# etc. and to provide an input for an external trigger.
Update: v2.2 has improved the usability by making it possible to dynamicaly change the notes and halt/loop points. The Stop button now stops the sequenence immediately instead of continuing to the end and you can select between play once, a preset the number of loops or an infinite number of loops.
Update: v3.01 has once again improved the usability by increasing the maximum number of notes from 32 to 96 with the ability to Save and Open your sequencies. Control and Help menus have also been added.
Update: v3.03 has added an external trigger so the synth can be triggered and stopped with other effects such my Drum Trigger program. I have also rearranged all the control buttons to look similar to the Drum Trigger.
Update: v3.04 has added external controls for varying the overall tempo.
3800 Synth interface.
How it works, v3.0:
(a) Set up the notes you want by setting the binary code check boxes, if you do not want to use all 96 then select the Halt check box next to your last note. The binary codes and Halt check boxes can be changed while the sequencer is running.
(b) Select the time duration between each note, in 0.025 second increments, with the Slower/Faster buttons. If you want a delay between each repeat then set the time with the Longer/Shorter buttons in the Loop Control area, again in 0.025 second increments.
(c) In the Loop Control area select the check box 'Infinite Loop ON/OFF' if you want notes to play in a contineous loop or...
(d) If you want to select a preset number of loops select the check box 'Loop ON/OFF' in the Loop Control area. Use the More/Less buttons to select the number of loops. If neither Loop check boxes are selected the sequence will play once.
(e) Select the Start button to begin the sequence. The position of play is shown by the 'note' number being highlighted in blue.
(f) Select the Stop button to stop the sequence. On restart the sequence will start from the beginning.
(g) Select the Reset button to clear all the Note, Halt, Repeat check boxes and Loop Times ready to create another sequence.
(h) To save a sequence go to the menu bar and select File/Save As, a dialog box will open for you to name your file. Click Save to store your file. The default file extension is .seq
(i) To load a previously saved sequence go to the menu bar and select File/Open, a dialog box will open for you to select a .seq file. Once selected click Open and your sequence wil be restored.
RPi Sequencer v1.0 Screen
RPi Maplin 3800 Synth Sequencer v1_0 Script (just copy & past into IDLE 2.7).
RPi Sequencer v2.2.2 Screen
RPi Maplin 3800 Synth Sequencer v2_2_2 Script (just copy & past into IDLE 2.7).
RPi Sequencer v3.04 Screen
RPi Maplin 3800 Synth Sequencer v3_04 Script (just copy & past into IDLE 2.7).
RPi to Maplin 3800 Synthesiser Interface.