In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Peter Van der Zee wrote:

Hi Eagle:

The software A/D converter is very picky about precise timing....... it relies on balancing aggragate high durations and low durations of a simple R/C Digital to Analog converter (in this case a specialized  PWM). Any changes in interrupt durations at runtime will adversely affect the results.

I see in your code you are using WATCH statements. The A/D conversion will not work if those are active as the time interruption to display them corrupts the strict timing requirements.

I use my own assembler version of A/D all the time, and it works well. With some tweaking you can get it stable to 12 bits or more.... that is 1 part in 4096. And with some filtering/averaging approach 16 bits!

If as you say, everything is correct, and the source is indeed stable, then the only thing left is timing inconsistencies.

Cheers,

Peter (pjv)

---------- End of Message ----------


You can view the post on-line at:
http://forums.parallax.com/forums/default.aspx?f=7&p=1&m=317226#m317446

Need assistance? Send an email to the Forum Administrator at forumadmin@parallax.com

The Parallax Forums are powered by dotNetBB Forums, copyright 2002-2009 (http://www.dotNetBB.com)