In SX Microcontrollers, SX/B Compiler and SX-Key Tool, g_daubach wrote:

Stolzie,

please have a look at this thread: [url]http://forums.parallax.com/forums/default.aspx?f=7&m=75182&g=75409#m75409[/url]. It contains a lot of information concerning EMI problems.

I don't think that placing capacitors on each of the I/O pins will solve the problem. Much more important are bypass capacitors in parallel to the supply pins Vdd and Vss. As you are using the SX52, supply voltage should be fed into all available Vdd and Vss pins with separate filter caps across each pair of Vdd/Vss pins.

Reducing the clock rate alone also does not solve the problem, it only generates different (maybe even more) harmonics. I haver tested a system with 10 MHz clock that generated "nice" harmonics at 20, 30, 40,... up to 200 MHz.

Please have a look at the thread above first. If you have any more questions, I'd be glad helping you (if I can). 

BTW: On the boards I had tested, I use SX28s but I think problems are similar with all SX types.

Kramer said:

"I am sorry, but I cannot convienently locate the thread. It is quite long and I believe it occured in the last half of last year."

At the top right of the forum page, you will find a button named "Search". In the search dialog, enter "EMI" as text to be searched, and "last year" in the search period, and you'll find that thread conveniently.

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