[sdiy] Din Sync Master Implementation

[maxrest at gmx.de]

Doubling the incoming frequency would probable throw the 909 out of it's
sync as I do not send symetrical pulses.

But would you agree with me that muting the pulses shouldn't do any harm
to the machine? I mean they don't implement a PLL or something similar
that needs to settle and that might mess everything up..



> If the lag doesn't get any worse from repeating your test sequence
> then it doesn't sound like you are doing anything wrong or that the
> TR-909 is missing any of the clock pulses that you are feeding it. 
> Otherwise repeated stop/continue cycles should progressively throw it
> further out of sync.  What you describe with pressing the STOP button
> on the machine sorting out the problem seems to imply that the machine
> is occasionally in some erroneous state before you start your test and
> it is already once clock cycle behind from there onwards.
>
> I think I heard somewhere that the TR-909 doubles the MIDI clock
> frequency coming in, in order to provide finer resolution for the
> shuffle function.  Maybe a similar thing is done to the DINSYNC clock
> in, or it maybe acts on both edges of the DINSYNC clock to increase
> the resolution.  I don't have any hard reference for this so I'm not
> sure how it works, but maybe your problem somehow relates to this action.
>
> -Richie,
>
> On 2014-08-18 14:50, maxrest at gmx.de wrote:
>> It was behind the master and doesn't accumulate for sure.
>>
>> If it is in sync, I can start, stop and continue it for minutes
>> without any
>> problems. If it's not, it stays with the same shift. I checked the
>> signals and signals' count & timing with the logic analyzer, it looks
>> like intended and described.
>>
>> What I observed: when I press STOP on the 909, the next start from my
>> master get's the machine in sync.
>>
>> I found out about the 909 sequencer lag bug [1] but the machine I test
>> here is already updated. Does anyone know if they only fixed MIDI
>> synchronisation with it?
>>
>> Best,
>>
>> Max
>>
>>
>> [1] http://www.diprec.com/tr909/tr909.htm
>>
>>> Does the 909 fall behind the master or get ahead? After multiple
>>> cycles of your test sequence is the error cumulative. I.e. Does it
>>> fall progressively further behind if you keep repeating the test?
>>> Might help diagnose what's going on.
>>>
>>> -Richie,
>>>
>>> Sent from my Xperia SP on O2
>>>
>>> ---- maxrest at gmx.de wrote ----
>>>
>>>> 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
>>>>
>>>>
>>>>
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