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I'm working on a data logging project and would like to use all six analog inputs on my Arduino Uno R3. I've been able to get everything working, including writing to the SD card. However, with the shield installed I'm getting junk readings from a4 and a5. They work fine without the shield.

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The shield has pull-up resistors for I2C/TWI on pins A4 and A5. Special care (resistor bridge) needs to be taken if using these as analog pins. Please see the schematics for more details.

https://www.itead.cc/wiki/images/4/46/Sch_sd_shield_3.0.pdf

Cheers!

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