- carloop does take its power from the OBDII port on pin 16. It also is ground connected to both signal ground on pin 5 and chassis ground on pin 4. It probably should NOT be connected to chassis ground...
Getting deeper into the power issue, there are some protection diodes, capacitors and a voltage regulator to 5V in the power circuitry. The Photon/Electron/RedbearDuo is powered from the 5V and then outputs 3.3V. The CAN transceiver chip uses both 5V and 3.3V.
It looks like you need to do some troubleshooting. Can you try it on another vehicle and see if it works there? It should work when the vehicle is turned on to supply 12V to the OBDII port. If it still does not work, then you need to check the 5V and 3.3V on the carloop board. If it does work on another vehicle, then you need to check the connector on your car.
- I am confused with how you are getting any value back with issue #1. Sorry, I missed the part about the USB cord. In that case, any value you get back is meaningless until the carloop is fully powered. I assume this will work correctly once you get issue #1 solved.