16F88 + 2 Analog inputs

[ruijc]

Hi Tenaja and Bruce

Thanks for your support.

About the pin calling its noted

But Tenaja was also right about the input impedance.

The circuit was missing the pulldown resistors.
I checked the datasheet and it's confusing for me that in bold it states the max impedance for analog sources is 2.5K and at the bottom square states the max impedance for analog sources is 10K. Which should we follow ?

[tenaja]

Page 117 it states 10k in two places; text and notes. Page 190 says 2.5 with a NOTE, that says 10k is allowable with an increased acquisition time. That basically means extra time to charge the sampling cap. If you plug your numbers into equation 12-1 on pg. 117 you will get the appropriate time required. IIRC, the fastest it can go is around 30-35kHz, so with a 10k R, you'll have to slow it down to be reliable.

However, if you don't need 10bit accuracy, it probably doesn't matter.

[ruijc]

Got it

Thanks Tenaja

[tekart]

I had been struggling with the AD in the 16F88 recently and the answers you gave straightened me out. There's only so much documentation one person can digest and it is really wonderful to have this forum where we can learn from each other.

Thanks Tenaja