Capacitance Problem?

John Couture

I have a small board design of my own that works with the SX-Key and SX-Blitz.·

In standalone mode it works ok if I attach a wire (about 12" @ 22ga) to OSC2 and then to nothing else.

If I take the wire off and reset, it does not even get through the initialization routine leading me to think that·the wire serves as a sort of very weak capacitor.· Am I on the right track?

Additional info:

SX18 running at 4mhz, replaced the resonator because I thought that might be defective.· Schematic is attached if it is needed.· One modification that was made since that schematic is that I connected +5 on the LM7805 to the boards +5 (grin, yea, I know, that was a stupid oversight).



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John J. Couture

San Diego Miramar College

RobotWorkshop

What is the OSC setting you are using in your program? Have to tried different settings?

John Couture

FREQ 4_000_000

No I haven't tried other frequencies because:
1) resonator is soldered in
2) I have a LOT of 4mhz resonators (grin)

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John J. Couture

San Diego Miramar College

RobotWorkshop

Hello John,

Sorry, I was referring to the different OSC settings in the program code like:

OSCXT1
OSCXT2
OSCHS1
OSCHS2
etc.

You may have better results with another setting.

Robert

John Couture

Interesting. I would have never thought of that. I was using OSCXT2. I tried OSCXT1 and it worked! Robert you're a genius! Thank you!

I don't know why it worked but at least I know where to start looking.


For others following this thread, these settings are on page 49 of the SX-Key Development System Manual

http://www.parallax.com/dl/docs/prod/sx/SXKeyMan2_0.pdf


OSCXT1 - Normal Crystal/Res, 32khz to 10mhz
OSCXT2 - Normal Crystal/Res, 1mhz to 24mhz
OSCHS1 - High Speed Crystal/Res, 1mhz to 50mhz
OSCHS2 - High Speed Crystal/Res, 1mhz to 50mhz

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John J. Couture

San Diego Miramar College