little-scale — USB MIDI Game Boy Sync for $16, and DIN sync 24 (2011)

Three years after the Arduino boxes, the same job with no MIDI socket, no optocoupler and no power supply: a Teensy 2.0 that the computer sees as a MIDI device. This is also where the wiki gets a Game Boy link-plug pinout with wire colours.

Key claims#

• "a Game Boy LSDJ / Nanoloop 1.x sync device that shows up natively as a USB MIDI device, thereby requiring no drivers and no power beyond the standard USB connection… it only requires two connections for each Game Boy sync cable, and that's it." The Teensy 2.0 costs $16; you supply a USB A–mini B cable and a link cable to splice.
• The wiring, and it restates the LSDj/Nanoloop split:
  • LSDj: Teensy ground → link-cable ground; Teensy digital pin 0 → SC (serial clock).
  • Nanoloop 1.x: Teensy ground → ground; Teensy digital pin 1 → SI (serial in).
  • "Note that you will need to add a resistor to the connection going to SI in order to sync with Nanoloop 2.x."
• Firmware: a Teensy_GB_Sync.hex uploaded with the Teensy loader; source at github.com/little-scale/Teensy_GB_Sync. Editing it "you need to update the Teensyduino core to include MIDI Beat Clock messages".
• The link-cable pinout, read from the image ("Old '8bit' Plug", viewed at the cable):

with the caption "SI = Data In, SO = Data Out, SD/SC Flow control". Plug layout: 6 4 2 over 5 3 1.

• The DIN sync 24 update (2011-09-03), which makes the same box drive analogue gear: "Pin 2 is the sync 24 pulse output, at 24 pulses per quarter note and with a duty cycle of 3 milliseconds (regardless of the BPM). Pin 3 is the sync 24 stop / start pin, which outputs 5 V when playing and 0 V when stopped."

Where the 3 ms came from#

The DIN spec in the update is not from a datasheet — it is from the comment thread. burnkit2600 asked for MIDI→DIN sync; little-scale asked back "Is it a positive or negative pulse? How long is the duty cycle in terms of time?"; burnkit2600 answered: "I'd GUESS that 50% would work. I think DIN gear just senses the rising slope of the pulse. They are positive pulses. Roland uses +2.51 V, but +5V will probably work for most things. START/STOP is on another line — START trigger is +5V, STOP is 0V." He also notes his TR-77 uses a non-standard 8 ppqn. Four days later the feature shipped, with 3 ms rather than 50 %.

Practical takeaways#

• Splicing a link cable: green is the clock (SC), orange is serial in (SI), blue is ground on this plug — the two wires you need are green + blue for LSDj, orange + blue for Nanoloop.
• Pin 1 has no wire. A circuit that expects 5 V from the link cable (like the $1 box, s-little-scale-1-dollar-nanoloop-sync) has to take power elsewhere, which is exactly the failure a builder reported there.
• Nanoloop 2.x needs a series resistor on SI where 1.x does not.
• DIN-sync gear wants 24 ppqn positive pulses plus a separate run/stop line at 5 V / 0 V — the same box can therefore clock a Game Boy and a drum machine at once.

Relevance to the wiki#

Gives sync the physical layer — pin names, wire colours, which pin each program listens on — and extends the Game Boy sync story out to DIN 24, the format defmon's C64 adapter also speaks.

To verify#

• The wire colours disagree with the wiki's other source. sync carries nordloef's DMG-07 colours from the LSDj wiki — "brown +5 V, red serial out, yellow serial in, green clock out, blue ground" — where this table has brown = SD, orange = SI and no wire on VDD. Red = serial out, green = clock and blue = ground agree in both. The two describe different cables (a plain link cable and the DMG-07 four-player adapter) and colours vary by manufacturer; neither is corrected here.
• The pinout image is quoted from an unnamed hardware reference, not written by little-scale.
• A commenter on LSDj 4.5.5 reports the box only working if LSDj is already playing — pressing start after selecting MIDI sync "will just wait on sync forever"; unanswered.

Pages touched#

sync · lsdj · nanoloop · game-boy · little-scale · midi-in-trackers · live-tracking