3V3 Pin not working

The official PYBD running MicroPython, and its accessories.
Target audience: Users with a PYBD
Post Reply
kevinkk525
Posts: 969
Joined: Sat Feb 03, 2018 7:02 pm

3V3 Pin not working

Post by kevinkk525 » Wed May 26, 2021 6:43 pm

As I was trying to use multiple sensors with my Pyboard-D, I noticed that the 3V3 pin doesn't work. I doubt that this is just an input? Because there's no other 3V3 pin so it is the only source for the 3V3 voltage.. The 5V pin works just fine but when I connect the LED to the 3V3 pin, nothing happens. And that goes for both the Pyboard-D directly and the WBUS connector. So I removed all connected components and measured both pins with my DMM and the 5V pin shows 4.6V but the 3V3 pin shows 0V..
So I guess my pyboard is somehow broken?
Kevin Köck
Micropython Smarthome Firmware (with Home-Assistant integration): https://github.com/kevinkk525/pysmartnode

User avatar
Roberthh
Posts: 3667
Joined: Sat May 09, 2015 4:13 pm
Location: Rhineland, Europe

Re: 3V3 Pin not working

Post by Roberthh » Wed May 26, 2021 6:56 pm

No, it's not. It must/can be enabled by writing a 1 to pin Pin.board.EN_3V3. And you can also switch it off that way.

kevinkk525
Posts: 969
Joined: Sat Feb 03, 2018 7:02 pm

Re: 3V3 Pin not working

Post by kevinkk525 » Wed May 26, 2021 7:22 pm

oh.. thanks a lot! Somehow I missed that..
Kevin Köck
Micropython Smarthome Firmware (with Home-Assistant integration): https://github.com/kevinkk525/pysmartnode

User avatar
pythoncoder
Posts: 5956
Joined: Fri Jul 18, 2014 8:01 am
Location: UK
Contact:

Re: 3V3 Pin not working

Post by pythoncoder » Thu May 27, 2021 4:14 am

This is a feature to enable peripherals to be powered down in micropower applications. A bugbear in the original Pyboard was that, even with external power switching, power was still consumed via the I2C pullups; this required more external circuitry.

This was discussed with Damien and the Pyboard D has fixed these issues :D
Peter Hinch
Index to my micropython libraries.

kevinkk525
Posts: 969
Joined: Sat Feb 03, 2018 7:02 pm

Re: 3V3 Pin not working

Post by kevinkk525 » Thu May 27, 2021 5:24 am

Must be nice for bettery powered application. But would have been easier if the power pin was enabled by default and could be disabled manually not the other way around. But now I know :D Using other boards is just always full of surprises :)
Kevin Köck
Micropython Smarthome Firmware (with Home-Assistant integration): https://github.com/kevinkk525/pysmartnode

User avatar
pythoncoder
Posts: 5956
Joined: Fri Jul 18, 2014 8:01 am
Location: UK
Contact:

Re: 3V3 Pin not working

Post by pythoncoder » Fri May 28, 2021 4:16 am

Point taken, but I guess the reason is that after a wakeup from deep sleep (which is similar to a reset) you want the peripherals to start in an "off" state to minimise power consumption while the code gets started. My solution using external circuitry for the Pyboard 1.0 works in this way. The Pyboards run for periods measured in years on three AA cells.
Peter Hinch
Index to my micropython libraries.

kevinkk525
Posts: 969
Joined: Sat Feb 03, 2018 7:02 pm

Re: 3V3 Pin not working

Post by kevinkk525 » Fri May 28, 2021 5:35 am

Yeah that's a good point. Otherwise the state would have to be stored in some RTC memory and checked on wakeup, definitely more complicated.
Kevin Köck
Micropython Smarthome Firmware (with Home-Assistant integration): https://github.com/kevinkk525/pysmartnode

Post Reply