Digital Voice Recorder Problem...

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Hello,

I've put together Application note 355: Digital Voice Recorder and I've run into a major problem and hope someone may have an idea what the problem may be...

While recording, I seem to be picking up a noise spike that coincidently has the same frequency as the chip select line to the DataFlash. Right now I am assuming that I am picking up some type of switching noise from the chip select line but not quite sure.

I followed the application note precisely and used standard PCB layout guidelines so I am somewhat at a loss. The one glaring difference between my design and the Appnote is that I am using the Mega128.

Now could I be picking up this noise due to:

A) Improper Grounding
B) Malfunctioning ADC channel
C) Power supply issue
D) Code problem: May be accessing the DataFlash while an ADC conversions is in progress??
E) ???
F) ???

Any insight to what the problem may be would be great!!

Thanks,

OCNEK

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Is your chip select line on the same port as the Mega128's A/D channels? If so, move it. :)

As far as power supply, a 'scope should help on that. And/or add more capacitance, in case the dataflash has an increased draw when selected.

Lee

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.