Thursday, March 28, 2013

Arduino - pull-up resistors and SPI pins on the Mega

FYI.... if you are updating the version of your Arduino IDE, and you are using pull-up resistors and the pull-up resistors aren't working.... the behavior changed.  Instead of :
    
    pinMode(48,INPUT);
    digitalWrite(48,HIGH);
    
You now have to use :
    
    pinMode(48,INPUT_PULLUP);
    

Took me a bit to find that embedded in the release notes for the Arduino IDE version 1.0.1 .

Also, just as a reminder to myself, on the Arduino Mega's, the SPI pins are 50-53 - which I encountered when I used the board I had created for the alarm which had things mapped to those pins.  I've since modified the board on BatchPCB to use other pins, freeing those up and making things easier to use.

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