[sdiy] Din Sync Master Implementation

[maxrest at gmx.de]

Hello fellows,


at first I'd like to introduce myself: My name is Max and I run a small
company called E-RM in Berlin. We make clock generators and other audio
related custom projects.

I recently came across the task to implement a (Roland) DIN Sync master
in a microcontroller and found an old thread in the archives [1]
describing some details.

My implementation uses asymetrical clock ticks with a positive pulse
width of 5ms. There are three knobs to controll the transport, PLAY,
STOP/PAUSE and CONTINUE


Let's assume we are at the beginning and everything is stopped:

Start: Low, no clock Ticks

-> press PLAY

Start: Low>High -> 10-60ms delay -> Ticks start

-> press STOP/PAUSE

Start: High, no clock ticks

-> press CONTINUE

Start: High, Ticks continue

-> press STOP/PAUSE

Start: High, no clock ticks

-> press PLAY

Start: High>Low -> 10-60ms delay -> Start: Low>High -> 10-60ms delay ->
Ticks start



I tested my code with a Roland 606, 707 and 909. 606 and 707 work
pefectly fine with that scheme.

The 909 doesn't. Every now and then it is shifted by one clock cycle. I
do not understand this behaviour as everything I read implies that I
have to wait _at least_ 9ms from the rising edge on the Start signal
till my first tick. Otherwise it may get lost in CPU preperation time.

What does it mean that the 909 doesn't like longer wait times? Does
anyone have a clue on this?


Best,

Max


[1] http://dropmix.xs4all.nl/pipermail/synth-diy/2011-May/032373.html