gpio pins have reversed voltage

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I have a bananpro which I have run with both Slackwarearm and Armbian,. I just started having a look at using the GPIO pins and find that the the voltage on the 3.3V and 5V pins on the 40 pin header are reversed. For example, when I check pins 39 (GND) and 2 (VCC 5V) I get -5.3. When I check Pin 39 and 1 (VCC 3V) I see -3.3 then it changes to -1.8.

Does this indicate that something is fried on he board or might this be a firmware issue that can be fixed?

Edited by justwantin at Nov 23, 2015 23:25

About 6 months ago I accidentally connected it directly to 12V. Realised as I was inserting microusb that 12V was shorted across the power supply and pulled microusb away but that instant of 12V might have been what did it.

Yeah, probably, I fried the first raspberrypi I purcased too. I'm looking for online sales to get another Pro here in Australia. Looks like its out of stock where I purchased this one.

RE: gpio pins have reversed voltage

This is strange indeed....

Could you check the GPIO 3.3V and 5V from a different Gnd point anywhere else on the board.

Also try checking the USB port's 5V from the GPIO Gnd.

Are you sure you don't have the multimeter's leads reversed?

LOL it gets stranger! No I did not have the probes reversed. Usb was okay as I had a wireless dongle working fine. However,,,,,  I had tested this and the multimeter a fair portion of the morning., multimeter was okay read voltage correctly on things like batteries but the pro with different gnd/vcc combos always came up reversed.

Now I'm getting correct readings. The only thing that changed was that I had  removed the usb supply from the board and reconnected to test once more after reading your post... go figure?

......and I just ordered another pro online from a seller here in Oz. Probably won't be able to cancel now.... oh well... sigh!

OK back to where I was earlier today with enagtive voltage readings and those nowhere near the 3.3 and 5 volts. What changed? I took the dog for a walk and when we came back I powered up the pro using my phone charger, not the 5V 2A power supply I had used before I took the dog for a walk. Plugged to 5V 2A ps back in still negative. My successful tests one post up were after the pro had been off and unplugged for a couple hours. I'll do the same and test again before I go to work tomorrow morning.

You can also post the test picture here to let us see detail, it is really a strange status.

A LED with a series resistor connected between GPIO 5V and gnd would ascertain if the voltage is indeed reversed (which doesn't seem likely).

Yes indeed, I should have thought of that, The led lights up so this must be a multimeter problem. I can put the multimeter on a bettery and get a rrading with correct polarity but not the GPIO pins. I'll have to test my multimeter against another one.

too much noise/interference playing havoc with the meter?

or an error prone meter itself?

do check with a different multi'

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