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Raspberry Pi I/O pins.

DAB

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

Parents Reply
  • in reply to Jan Cumps

    That is a nice resource Jan.   It does seem to need some updates since it only covers the 26 pin P1 version of the RasPi rather than the current 40 pin versions. Also, the "electrical characteristic" diagram does show a note stating it is a "Speculative Raspberry Pi GPIO input output pin electrical specifications", so I would not take the values as an absolute.   

     

    It might be best to go directly to the Raspberry Pi Foundation folks for the final word.

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  • in reply to jomoenginer

      wrote:

     

    ...

     

    It might be best to go directly to the Raspberry Pi Foundation folks for the final word.

    you will be the 13.523rd down the row. I understand they want to protect bleeding edge technologies. But GPIO ?!?

  • in reply to Jan Cumps

      wrote:

     

    you will be the 13.523rd down the row. I understand they want to protect bleeding edge technologies. But GPIO ?!?

     

    Huh?!?

     

    Unlike the BeagleBoard devices, the Raspberry Pi is not an open source hardware device which I believe is well know by now.  However, I do believe the folks that create the RasPi do like seeing other folks create Hats and such for the boards as well like see the RasPi used in any environment it will fit in so image they would be a good source for such an effort.

     

    Who is doing something "Bleeding Edge" ?

  • in reply to jomoenginer

    No one is doing bleeding edge;. That's why I don't understand why the GPIO standards aren't officially published. People have to look to not-actually-used devices to get specatulative/comparative  specs, and derive from that.

    With the BB, the specs are in the domain. No non disclosure needed.

  • in reply to jomoenginer

    Hi Jon,

     

    Keep in mind, the RPi line was all about creating an inexpensive computer for internet access.

    Any uses beyond that are beyond its intended specifications.

     

    The Beagle Bone was designed to support a wide variety of embedded uses, so it makes sense that it was designed with more robust I/O.

     

    I was clearly implementing an RPi into a project that stretches its abilities.

     

    I made my post so that everyone would be aware of these limitations if you want to task a RPi beyond its stated goals.

     

    DAB

  • in reply to DAB

      wrote:

     

    Hi Jon,

     

    Keep in mind, the RPi line was all about creating an inexpensive computer for internet access.

    Any uses beyond that are beyond its intended specifications.

     

    The Beagle Bone was designed to support a wide variety of embedded uses, so it makes sense that it was designed with more robust I/O.

     

    DAB

     

    Yeah, I know that which is why I stated what I stated since it did not seem to be the intent of the post.

     

    There is the Raspberry Pi integrator Programme if you are looking to go beyond the basic usage of the Pi.

    https://www.raspberrypi.org/blog/raspberry-pi-integrator-programme/

  • in reply to DAB

    Don, I used both of the board families and they are both excellent.

    Hardware wise, it’s hard to make a choice. I may prefer the BB a tad more because of the real time capabilities. But those are complex and not very well supported by their Linux distributions.

     

    The Pi is the winner for community support. Hands down.

    But then it’s so hard to get their GPIO  hardware specs. Why?

  • in reply to DAB

    ... as a side note, the Raspberry should be perfectly capable of handling your i/o requirements. It’s a decent board. Nothing in your  use case seems to be beyond its capabilities. Can you show us the relevant code?

  • in reply to Jan Cumps

    Hi Jan,

     

    I cannot share details as it is a project under an NDA, but the circuit is just a simple transistor driver to boost the current drive from the RPi to another SBU device.

    As I said, I was just surprised that the outputs from the RPi varied all over the place.

     

    Now that I know what is going on, I can adjust the circuit accordingly.

    I just wanted everyone here on element14 to be aware.

     

    DAB