little-scale — $1 Nanoloop MIDI Sync (2009)

The minimum viable sync box: one CMOS chip and no microcontroller, syncing nanoloop to MIDI clock. It is the design people actually built, and the comment thread is a good record of what goes wrong.

Key claims#

• "the only component that is needed is the 4017 IC, which cost me about $1." Powered from the Game Boy: no battery, no USB.
• The full wiring, verbatim (his own headings):
  • 4017 power supply: PIN 16 → GB LINK 5V; PIN 8 → GB LINK GROUND.
  • 4017 operation: PIN 4 → PIN 15; PIN 14 → PIN 16.
  • GB sync signal: PIN 3 → GB LINK SERIN (the Nanoloop pin — s-little-scale-arduino-gameboy-sync-boxes).
  • MIDI input: MIDI PIN 4 → 4017 PIN 13; MIDI PIN 5 → 4017 PIN 8.
  • "when looking at the back of a female MIDI connector, the middle-left pin is pin 4 … the middle-right pin is pin 5".
• What it deliberately omits: "This schematic does not adhere to MIDI hardware specifications (there is no optocoupler, for instance) and there are no filter or bypass caps for the Game Boy power supply. So these are the sorts of things you might like to add (or not). However, I have it working in a very stable fashion 'as is'."
• The standing limitation: "you can only send MIDI clock messages on the output that is connected to the Game Boy, because other MIDI messages will mess up the synchronisation. Although some may find this a little limiting, I always tend to use a dedicated port for any MIDI clock sources anyway."
• Use: build it, set the sequencer to output MIDI clock, "Set your Nanoloop to external sync. Press play and party!"
• It does not do LSDj — "Other things can be made that will work with LSDJ, but not this particular design" — and not a Nintendo DS.
• The design spread: 8BC user liquidcalm built one in a case a month later, and the comment threads are full of people building it ("I had this on my 'to do' list and figured it'd be a gigantic time-eater. I had no idea it was so simple").

The unresolved objection#

Commenter electri-fire reads the wiring as wrong and is never answered:

"I think there could be an error in the description of the connections. It says 'Connect 4017 PIN 14 (= Clock In) to 4017 PIN 16 (= 5 Volt).' Thus the 4017 is not recieving Clocks. And 'Connect MIDI PIN 4 to 4017 PIN 13 (= Clock Enable)' — Pin 13 should usually be held High (at 5 Volts)."

Against that stands little-scale's "I have it working in a very stable fashion 'as is'" and a number of successful builds. Both stand; the wiki does not resolve it. (A 4017 does advance when CLOCK INHIBIT falls while CLOCK is held high, which would make the described wiring deliberate rather than mistaken — but that reading is an inference, not something either party states.)

What the failures teach#

• Power: one builder failed "because the Powersupply of my Linkcale is missing", then succeeded — "Power is now coming from Gameboy itself by just putting the circuit in it." Not every link cable carries the 5 V line; see the pinout in s-little-scale-teensy-usb-midi-sync, where pin 1 VDD35 has no wire at all.
• Cable colours: "How can i tell which wire is which on my link cable?" is asked repeatedly and never answered here.
• A partial failure worth recognising: "My nanoloop moves two steps when I turn my drum machine on but then nothing."

Practical takeaways#

• For Nanoloop alone, a $1 decade counter and a MIDI socket is the whole build — the microcontroller in the bigger boxes buys you LSDj, START/STOP/CONTINUE and many outputs, nothing else.
• Give it a dedicated MIDI port carrying clock only.
• Power it from the Game Boy, and check your link cable actually has the 5 V conductor before blaming the circuit.

Notable quotes#

"at least you won't be wasting much money because the only component that is needed is the 4017 IC, which cost me about $1."

Relevance to the wiki#

The cheapest entry point on sync's Game Boy side, and a concrete illustration that Nanoloop sync is a bare clock on the SERIN pin.

To verify#

• The divider ratio the 4017 performs is not stated. Nanoloop wants 12 ppqn where MIDI beat clock is 24 ppqn (s-little-scale-arduino-gameboy-sync-boxes), so a halving is what the circuit needs, but the post does not say so.
• MIDI pins 4 and 5 are wired directly to the chip with no optocoupler and no current-limiting stated beyond what the source provides — outside the MIDI electrical specification, as he says.

Pages touched#

sync · nanoloop · game-boy · little-scale · midi-in-trackers