[Pd] Serial port out

[Svante Hermansson]

Christian Klippel wrote:
  > Am Freitag, 17. November 2006 17:26 schrieb Steffen:
>> I read about it in Delton T. Horns Music Synthesizers: A Manual of
>> Design and Construction, if i recall correct, where the author
>> suggested to use a S/H in connection with such a converter to save
>> CPU power (when one wanted to keep a given CV for a period of time
>> (faster then the port)).
>>
> 
> this is only usefull if you want to digitize a changing signal. you use the 
> s&h circuit (usually just a capacitor and a switch) to "freeze" the current 
> value, so it stays stable while you digitze it. to digitize a signal, you 
> basically need a dac, s&h and comparator. you load the s&h, set a value at 
> the dac, and compare the two voltages with the comparator. you change the dac 
> value so long until you have a match between the two voltages. then you 
> discharge the s&h, and go ahead with the next sample.

Not only useful for digitizing an analog sample into the digital world, 
but also useful as a multiplexer. If you build a converter using one 
single ADC, you could share it to say 8 channels by sending them one at 
a time. Often (but not always) cheaper and easier than using 8 normal 
ADC's. Multiplexing with S&H works even on a low pass filtered 
PWM-signal if thats what someone (?) was planning on using...

mvh//Svante - with a homebuilt midi to 8-channel CV somewhere in some 
drawer...