microSD Breakout issue

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festus hagen
 
Posts: 3
Joined: Thu May 24, 2012 6:32 pm

microSD Breakout issue

Post by festus hagen »

Hi All,

Sorry, But I just couldn't come up with a better title/topic ... Or what to search for either!

Here is the deal, I am unable to get to the documentation it appears ladyada.com is having issues, so I hooked it up off the cuff, it works fine as far as I can tell, every test has worked including allowing it to run for a couple hours recording TONS of data ...

Except one very strange thing happens, get within 1/2 inch of it and the LED comes on!
Yes, you read that right, just waving my hand within 1/2 inch of the board and the red LED comes on and remains on until either activity turns it off or I wave my hand over it again!

So, I suspected my complex layout, So I minimized it to just the Arduino and microSD breakout ... Still does it!

Any ideas.

5v -> 5v
gnd -> gnd
clk -> P13
do -> P12
di -> P11
cs -> P10 (and set in code)
cd -> P9 (Not currently used)

Thanks

-Enjoy
fh : )_~

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john444
 
Posts: 443
Joined: Sun Mar 04, 2012 2:42 pm

Re: microSD Breakout issue

Post by john444 »

Hi Festus Hagen,

What you are experiencing can occur when an input pin of an IC like the Arduino does not have a pull-up (or pull-down) resistor. Without a circuit to pull the input high or low, it 'floats'. Any static charge in close proximity can cause the internal transistor to change from 'on' to 'off' or vise versa.

For each pin you programmed to be an input - check that the internal pull-ups are enabled or attach a high value resistor to + 5-V. The pull-up resistors could be any value from 10-K to 1-M. You do not need pull-up resistors for output pins.

You may be able to find the offending input with a little testing. Attach one end of a lead-wire to ground. Secure a 1-M resistor to the other end of the lead-wire (or just hold the lead-wire and resistor-lead together). Then systematically touch each pin on your circuit with the resistor-lead until the change occurs. In you case the LED comes on. If nothing seems to happen, then move the lead-wire from ground to +5 (if everything is running on 5-V) and do it again. Don't do the test without the resistor.

Good Luck,
John

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