[sdiy] 1 bit serial stream delay approaches..

[Jean-Pierre Desrochers]

This is a very good approach.

As i read back all the posts I received on that topic
sure I won't go with digital gates and complicated hardware..
Some C code digesting times are ahead..
Thanks Guys!
JP

 On Wed 19/09/12 13:41 , "Richie Burnett" rburnett at richieburnett.co.uk sent:
> > If so, a PIC should do the job for you.  with 8K
> bytes of RAM, you have > 65536 bits.  You could
> > shift the input gate through as many bits/bytes
> as you need.  A little > arithmetic says you
> > should get good resolution even if you use only
> one bit per byte (0.00061 > seconds per delay
> > sample).  Use all the bits (more complex
> program) and get 8 times the > resolution.  A PIC with
> > and ADC can read a pot to set the delay
> time.
> This is the route I would take also, merely because of its simplicity. 
> Even a low end-micro with just 256bytes of RAM would give you more than 5
> seconds of delay with 2.5ms timing resolution.
> 
> I'd just add one implementation issue which surely goes without saying for
> the seasoned programmers, but might be overlooked by someone new to
> embedded programming...
> 
> You don't actually shift the signal through all of the bits in the memory,
> as it would be incredibly time consuming to have to repeatedly move each
> bit of data to the next memory address for the entire memory space.  Instead
> you think of the memory space as a circular buffer with a read pointer and
> write pointer.  The write pointer makes its way repeatedly through all of the
> available memory, and the read pointer runs along behind the write pointer.
> How much it is behind determines the amount of delay.  Setting up two
> memory address pointers for circular addressing is much less hassle than 
> continuously shuffling data through memory.  You can also easily implement
> a multi-tap delay by using a number of different read pointers with different
> offsets behind the write pointer.
> 
> -Richie,
> 
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