OK, I'm really intrigued but I admit to not understanding this.  I am
currently in a prototype stage using a PIC17C42 and an external ADC.  I
would really like to get more resolution.  Is there any chance of a more
detailed explanation?  What I don't understand is how the square wave
increases the resolution when the ADC (an 8-bit for example) can only
report 256 decision levels.  Thanks!


Regards,


Gerald Morrison
Product Development Engineer

Smart Technologies Inc.                Direct: 403-228-8557
#600, 1177 11th Avenue S.W.            Fax: 403-245-0366
Calgary, AB, Canada  T2R 1K9           email: gerald@cal.trlabs.ca
http://www.smarttech.com


> I regularly get 12-16 bits of precision out of an 8-bit (PIC 71 or 73/74)
> doing the following:
>
> Take your samples are _very_ regular intervals, while applying a high
then
> low signal (at 50% duty cycle) such that the signal is pulled high or low
> by 1-bit of resolution (1 bit of 8).
>
> The values used for the resistor R1 and cap C1 are determined by the
drive
> of your analog signal, its level, and the amplitude of the square wave
you
> are providing.
>
> (The little "o" is the junction of the components).
>
> Wire this up and look at it with your scope (use a 1x probe).
>
>
>                 +----R1------< square wave source
>                 |
>                 |
>                 |
> Analog In>----o------------> input to A/D converter
>                 |
>                 |
>                 |
>                 C1
>                 |
>                 |
>                 GND
>
> Andy
>
> ==================================================================
> Andy Kunz - Montana Design - 409 S 6th St - Phillipsburg, NJ 08865
>           Hardware & Software for Industry & R/C Hobbies
>         "Go fast, turn right, and keep the wet side down!"
> ==================================================================