Cannot see 3.3v on P24?



  • Hi all

    I have my WiPy2 on the expansion board powered over USB - all seems to be working (I can connect over wifi, blue light flashing, can modify code etc), but when I try and measure the voltage on P24 using a multimeter it shows 0v. When I look at P26 I see ~5v, and I see voltages on other pins, but nothing on the 3.3v line - which I was hoping to use for powering a peripheral. Any ideas how this could be happening?



  • That's why I hate fool proof devices: they make a fool out of you.



  • Looks like it's my own fault - according to the manual my multimeter switches to 'continuity check' mode 'around 3v'[sic], so I believe the wipy is probably ok, but 3.3v counts as 'around 3v'. (I found this after trying similar tests on a raspberry pi and getting similar results, though the meter measures my lab power supply correctly, I guess the impedance differs).

    Thanks for the suggestions, they helped convince me that it was probably me and not a hardware fault!



  • It's all pycom soldered. If the processor is running off the 3.3v supply then there could be a problem somewhere between that and the output (I tried measuring the voltage on the pin on the Wipy itself, but that showed as 0v as well.)



  • Did you solder the headers yourself by any chance? Sometimes the solder may not have reflowed correctly and the pin appears to be 'on air'... in that case just give it another touch with a bit more heat.

    Can also happen sometimes even when headers are soldered at the factory.



  • Re Pins: I just chose at random - mostly to see if I was getting any readings - assuming my multimeter was playing up - P20/P21 were around 2.2v. They haven't been programmed to do anything

    Re When: This was once the board was up and I had connected over wifi - I wasn't programming it at the time.

    Re P24: - yes, shown as 3.3v on schematic. 3rd pin from top at right - measures relative to 0v (2nd pin on right). 5v was found on top right pin.



  • and I see voltages on other pins
    on what pins and what voltage? And when do you see voltage on pins - after start up or when you programm it?
    Without set it to high pins except some special should have 0V
    and as P24 you mean 3V3 pin?


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