A5 (SCL) pin prevents new shield to turn on

Hi there,

I designed a new Arduino Uno R3 shield that uses I2C to read a bunch of sensors and the shield does not work (it doesn't turn on) when the Arduino boots with A5 (SCL) pin connected to the shield.

What is wierd though is that if I boot up the Arduino with A5 (SCL) disconnected from the shield and I connect it after the Arduino is on, the shield works perfectly.

Anybody has any idea why this is happening and how to fix it??

Cheers,
Leo

It sounds like it might be miswired or a transient is getting into A0 causing it to latch up. Be sure to check the grounds they are critical. You might want to post the schematic. This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil