Pickit2 & ADC sampling

[Mosaic]

Hi all:
It appears that the Pickit2, if left connected to ICSP pins and a PC USB does influence the results by introducing some type of noise to 16F adc sampling

My experience was for 8 x 10 bit ADC samples summed and divided to 11bit accuracy for voltage accuracy to 2 dec. places. The Pickit2 connection created a noise of up to +/- .08V in the result.

Took a while to trace it down , but pulling it off the ICSP immediately stabilized the readings.

 

[Wp100]

Don't think it will be the Pk2 itself thats causing the problem, more likely the USB voltage its powered with.

Also the VDD fro the Pk2 is only rated at about 25ma, is your circuit getting near its max.

Have experienced other wierd problems when running from USB voltages that simply never happen with a basic voltage regulator circiut.

 

[Mosaic]

Wp100 you misunderstand, the Pickit2 wasn't supplying any power, the circuit was self powered when the errors occurred. It was connected to the ICSP alone. By powering down the circuit I can directly reflash the hexcode from the Pickit2, which only then supplies power.

 

[Nigel Goodwin]

Hanging un-needed hardware on anything is likely to disturb things somewhat, particularly if it's connected to a nasty noisy PC