Good day to you all,

I am looking to power my Raspberry Pi 4b from an external 5v supply. I know I could just put the 5v supply to the raspberry pi 5v/GND pins and power it this way but this does bypass the polyfuse and other protections.

So I got a USB C cable and checked it worked by powering up the raspberry pi using a small USB C PDO travel adaptor. I then cut the cable into 2. I had the following conductors inside the cable... Red White Green Blue 2 bare conductors Outer metal braid

To find which conductors are the positive/Negative for power, I plugged in one end of the USB C connector to the travel adaptor, then with the cut end I presume that Red will be the positive voltage but trying to find the negative is a bit troublesome but after hooking up the multimeter to see what would give me I could not find 5v With Multimeter positive on RED I got the following voltages Multimeter negative on Blue I got -3.35v Multimeter negative on Green I got -0.16v Multimeter negative on Blue I got -0.2v Multimeter negative on metal broad I got 0v

Does anybody which 2 conductors I would need for the positive and negative to power my Raspberry Pi from my +5V external supply

I don't seem to have any other way to find out apart from plugging in the connector to my Raspberry Pi and connecting the 5v source to various conductors to see what combination powers up the Pi and not blow it up.

Thanks PS This could also mean that thwe color of the wires is non standard

  • 1
    \$\begingroup\$ Why do you say you don't have any other way to find out the pin mapping? You have a multimeter. You can map out the pins by figuring out which wire shows 0 ohms to ground and 0 ohms to 5V input? \$\endgroup\$
    – Justme
    Nov 20 at 20:45
  • 1
    \$\begingroup\$ Unless both ends of the cable are plugged in there won't be 5V on the cable. USB-C relies on a basic handshaking system to turn on the power. \$\endgroup\$
    – Finbarr
    Nov 20 at 21:09
  • \$\begingroup\$ A bunch of pins needs to be bridged. Here's a diagram taken from Quora - qph.cf2.quoracdn.net/… All in all, a USB-A to USB-C works out of the box. \$\endgroup\$
    – MiNiMe
    Nov 20 at 22:12


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