I have made a little project using WebIOPi, and it works like a charm. However, I have noticed that during the boot of the Raspberry Pi, all I/O pins are put at 0.6 V. This is enough to trigger my transistors and causes quite a lot of problems.

I am running the newest versions of WebIOPi and Raspbian, using a ABElectronics IOPi Expander.

How do I control the Raspberry Pi's behaviour during boot or is there a workaround?

  • 1
    You could just add a/increase the size of the resistors on the base of the transistors to increase the voltage required to trigger them.
    – Wilf
    Jun 20, 2014 at 21:29

1 Answer 1


The state of the GPIO during startup is undefined, but on boot all should be set as input. If Console I/O is enabled TxD & RxD (8 & 10) will be configured for serial IO. There are on-board 1.8KΩ pullup on I2C (3 & 5). If you need to define the state of other pins you should include pullup resistors.

  • 2
    I think pull-down would be more appropriate in this case, as pull-up would exacerbate the problem.
    – Gerben
    Jun 21, 2014 at 11:21

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