How to Test an older RTC/SD card logger
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How to Test an older RTC/SD card logger

by SquidTeeth on Thu Mar 21, 2013 8:09 pm

Hi there, I have the previous version of the RTC/SD data logger shield that has been working fine until recently. I received an error that the SD card wouldn't initialize or wasn't present. I checked the original SD card on PC and MAC and it still had previous log files from other tests, but a different card, re-seating the original card or formatting it made no difference. On the example CardInfo Sketch I get the error "initialization failed" (chip select set to pin 10). I started checking for possible mistakes I had made when I noticed that Pin 11 no longer outputs high or low with the shield in place, using a LED, resistor and the blink sketch, although it is fine when the shield is removed. The other thing I checked was the voltage at the card pins 4 & 5 is 3.3VDC

The RTC side of things works fine, and if I comment out the section where it initializes the SD card my sketch will run, but not log.

I am not sure how I could test the 74AHC125N, as all the other components seem to indicate fine.

I hope that the Pin 11 thing might give you a clue
BTW this is the SMD Uno and the older version of the RTC SD logger shield
Any thoughts will be appreciated.

Darren
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Re: How to Test an older RTC/SD card logger

by adafruit_support_bill on Thu Mar 21, 2013 8:21 pm

Pin 11 no longer outputs high or low with the shield in place

the voltage at the card pins 4 & 5 is 3.3VDC

Pin 4 should be at 3.3v. Pin 5 should be the SPI clock signal on Arduino pin 13. That combined with the Pin11 problem leads me to suspect that the problem is in the 74AHC125N level shifter.
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Re: How to Test an older RTC/SD card logger

by SquidTeeth on Tue Mar 26, 2013 10:09 pm

Sadly the Digikey order arrived and the newly installed 74AHC125N wasn't the problem, but on the good side it's in a socket now...

Pin 11 on the SD/RTC shield now is passing information to an LED, but it still can't see the SD card itself. You also mention a clock on pin 13, although that is not in my sketch, should i avoid that pin, or any others?

Any other thoughts?

BTW what does the 125 chip do, There was a mention of it as a Level shifter to protect the SD card, but i can't seem to find that anymore.
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Re: How to Test an older RTC/SD card logger

by adafruit_support_bill on Wed Mar 27, 2013 5:50 am

Arduino pins 10 through 13 are the SPI interface to the card. You don't control them explicitly from your sketch, but they are used by the SD library to talk to the card. These are the only 4 pins related to SD card access.

The 74AHC125N converts the 5v Arduino logic levels to the 3.3v expected by the card.

The only other thing I can think of it to try a different Arduino. It is possible that the problem is there too.
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Re: How to Test an older RTC/SD card logger

by SquidTeeth on Wed Mar 27, 2013 11:05 am

Thanx a bunch for you help. I'll have to pass on the back up arduino test until more work falls into my lap. If I find out anything, I'll post again.
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