I have a Pi Zero W, which works when connecting to wireless when powered via the 5v USB and also has a decent console resolution on the HDMI port.

However, when powered with 3.3v using a custom carrier board both the console resolution is lowered and the zero reboots as soon as it is told to connect to the wireless network. When this happens, leaving the wpa_supplicant.conf file intact will cause an infinite reboot loop which only stops when the wpa_supplicant.conf file has the network section removed using a different machine.

I am at a loss.. does the wireless chip require 5v to operate?

1 Answer 1


After watching the power rails.. the 3.3v rails drops when the wireless is turned on.. this voltage drop is causing the reboot issues..

  • The 3.3V rail is inside the regulator, i.e., if you power from 5V, you get a regulated 3.3V on the 3.3V rail. If you try to power from the 3.3V rail you will get whatever it is you are supplying and prone to whatever flaws that supply has.
    – goldilocks
    Commented Apr 12, 2017 at 21:42
  • If you use the HDMI to a display, you probably use a USB keyboard and mouse as well and they need 5V.
    – Jot
    Commented Apr 12, 2017 at 22:35
  • @Jot No, only use the HDMI to verify the bootup or reboot loop..
    – Richard
    Commented Apr 13, 2017 at 22:30
  • @goldilocks yes, that is what was determined yesterday after scoping it out. The carrier board takes a 12v rail, then regulates to 5v for a USB device which is fine, and the 3.3v for the pi.. the issue is since the power is being sent through modulated with data, and several other things are powered, we are trying to figure out how to give the PI the 610mA it wants to power on the wireless (note the spike is not noticeable, but from a power supply current limited, anything less than that and a reboot would occur) when 480mA may be the maximum available, which is fine for everything else..
    – Richard
    Commented Apr 13, 2017 at 22:37

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