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Member's Forum Raspberry Pi I/O pins.
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Related

Raspberry Pi I/O pins.

DAB
DAB over 7 years ago

Hi all,

 

I was doing some testing yesterday and discovered that the I/O pins on the RPi come up with interesting voltages on powerup.

 

I had just assumed that they would all come up at ground state, but we measured several pins and found them at 0.7, 1.2, 1.7, and 2.7 volts output.

 

We were trying to debug a driver circuit I designed, but noticed the default was at 1.2 volts and thought we might have a defective board. So we installed a brand new RPi 3 and found the pins at the above stated levels.

 

I am VERY disappointed in the RPi designers for not defaulting the pins to ground state until they are accessed by software.

 

Hopefully, they will correct this oversight in the next version.

 

Having random output levels could really do some damage to external circuits wired into an RPi.

 

DAB

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  • Jan Cumps
    Jan Cumps over 7 years ago +5
    This article shows the electronic setup of the Pi’s pins, and has the voltages documented. GPIO Electrical Specifications, Raspberry Pi Input and Output Pin Voltage and Current Capability
  • colporteur
    colporteur over 7 years ago in reply to Jan Cumps +3
    Awesome resource Jan! I program GPIO but my electronic technology background is a constant undercurrent to understand the why something works. Pull up and pull down functions on GPIO pins, which I have…
  • DAB
    DAB over 7 years ago in reply to Jan Cumps +2
    Thanks Jan. Yes the potential voltages on the pin matches my measurements so that means I was not doing anything unusual. I was just not expecting that level of variance. Now that I know, I can look at…
Parents
  • Jan Cumps
    Jan Cumps over 7 years ago

    This article shows the electronic setup of the Pi’s pins, and has the voltages documented.

    GPIO Electrical Specifications, Raspberry Pi Input and Output Pin Voltage and Current Capability

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  • colporteur
    colporteur over 7 years ago in reply to Jan Cumps

    Awesome resource Jan!

     

    I program GPIO but my electronic technology background is a constant undercurrent to understand the why something works. Pull up and pull down functions on GPIO pins, which I have used in programing,  make sense in the drawings. I have bookmarked the resource and will no doubt use it in the future. Thanks for the share.

     

    Sean

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  • colporteur
    colporteur over 7 years ago in reply to Jan Cumps

    Awesome resource Jan!

     

    I program GPIO but my electronic technology background is a constant undercurrent to understand the why something works. Pull up and pull down functions on GPIO pins, which I have used in programing,  make sense in the drawings. I have bookmarked the resource and will no doubt use it in the future. Thanks for the share.

     

    Sean

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