Korg Volca Sync

Simple arduino based module for synthesizer/sequencer synchronization.

Features

• 4 synchronization channels (easily extendable by CHANNEL_COUNT).
• every channel can be delayed in 256 steps up to +/- 1/16th note (positive and negative delay possible).
• every channel supports half-step mode (only pulses every second sync step).
• song tempo configuration (in BPM).
• song position display.
• global start/stop.
• settings are persisted in EEPROM.
• changing the channel delay will slowly change the delay (immediate changes confuse some devices).

Why?

I've had a lot of problems syncing my devices. No matter which device is set to master, nothing really worked 100%.

• Volcas have huge problems with MIDI sync
• Volcas emit a single pulse upon startup (=> device chain is out of sync)
• Arturia Keystep stops forwarding syncs when sequencing is stopped
• Monologue emits an additional sync when play is pressed (WTF?)
• Sequenced synths with (relative) long attack times sound off-sync with the kick-drum. A negative sync delay would fix this issue.

What do I need to build this?

• ATMEGA328 + Crystal
• PCF8574 I2C LCD Controller
• 16x2 LCD Display
• Some buttons
• A rotary encoder

How does the sync pulse look like?

This is what four delayed pulses with a PULSE_LENGTH of 30 look like in the scope (two of them are half-step only):

Ok, how does it look in action?