When i came to Synth DIY my first point of contact has been EFM. There have been quite a few
kind and cool people, and i know Dave from these days. We stayed in contact all the time,
talking about the old EFM designs and sharing our ideas. I think he is the most enthusiastic EFM builder ever...
In early 2010(?) Dave told me about his new project: a MIDI2Clock module without using a PIC,
just logic ICs! I liked it from the start, since i cannot write/understand code and all that
stuff. What intrigued me the most was to have the decoded MIDI and all the clock signals available on
headers for futur use on extension boards, that might come. Expandable system! Great!
Dave: The MIDI2CLOCK (M2C) takes a MIDI input, and outputs 24PPQN CLOCKS, START, CONTINUE and STOP
pulses. These can be +5V or +10v by installing links or pairs of resistors. There is also an
onboard 2-stage divider network with GATE and TRIGGER outputs, that allows different time signatures, pulse divisions and pulse widths to be set up, using just a rotary switch and 8 SPST changeover toggle switches. No menus or LCDs, or any of that malarkey.
It handles MIDI clocks, not MTC (midi timecode) - MTC is a completely different beastie....
The circuit has been tested operating from 1 BPM to 250 BPM, and will track tempo changes
smoothly. The gate length is proportional to the tempo, so slower tempi give longer gate
There are LED indicators for the various outputs, and a MIDI receive LED that lights when
any MIDI signal is present at the circuit's MIDI input.
As well as that, there is a pin-header on the PCB that carries decoded MIDI as CMOS-compatible
8-bit parallel +5V logic, along with other useful internal circuit signals. Other pin-headers
on the board allow for expansion to further circuits, eg, more divider stages, or remotely
controlling the action of the switches. They could even be used to decode other types of
MIDI messages with extra circuits , but that is for the truly adventurous :)
There are pin headers too for the transmit section of the main processor (CV to MIDI). It is
not used in the basic design, but is there for those who wish to experiment with it. Additional
circuitry will need to be added in order to use this function.
There are no programmable ICs used, and no calibration is needed, so it can be simply soldered
up and is then ready to go. All components used are in current production as of may 2nd 2011,
with only one slightly unusual IC, which is still being manufactured, and is stocked by Digikey,
Debco.com, Jameco, Farnell and others.
Here you will find the building documentation for the PCB i made: