Sonim XP 3410 3.5mm 4 pin Charger Cable Pinout

[BenJ805]

I've looked everywhere online, I even called Sonim and asked them directly. Still can't come up with a pinout for the 3.5mm 4 pin to USB-A wire.

It's similar to this one listed, but I  have no idea if it uses a standard or is custom.

http://connector.pinoutguide.com/4_pin_3.5mm_2.5mm_plug/

[emerysteele]

I have a Sonim XP1520 on hand & just tested the pinout with a multi-meter.
The Sonim XP1520 & XP3400 use the same charger. So I assume the XP3410 would be the same as well. But you may want to double check that with Sonim.

Anyways the pinout for the XP1520 is:
Tip (1): Data +
Ring (2): Data -
Ring (3): GND
Sleeve (4): VCC

Similar to an iPod Shuffle cable but with the data lines flipped.