The FLIR ONE is a thermal imaging camera attachment for iOS and Android devices.  The FLIR model for Android uses a micro USB connector while several newer devices including the Nexus 5X employ the newer USB Type-C connector.  Many micro USB to USB Type-C adaptors do not support the 5X being the host and the FLIR being the device (using a USB C to C cable to a Mac, for example, the Mac is the host and the 5X is the device).   Using a non-compliant connector the FLIR ONE Android app does not see the camera.

The VicTsing USB 3.1 Type-C to Micro USB Convert Connector  does work with the Nexus 5X and FLIR ONE.  The FLIR app connects to the camera and appears to work well.

Web searches return warnings about using un-tested micro USB to USB C adaptors or USB Type-C to female micro USB cables for charging.  A good discussion by Geoff Hoff can be found here.  Using the app Current Monitor by Eric Johnson, the VicTsing USB 3.1 Type-C to Micro USB Convert Connector appears to be safe to use for charging.  The charge current started in FAST mode, then when the phone reached 95% charge it switched to TAPER mode and reduced current through 100%.  Nonetheless, I plan on using the adaptor only for the FLIR and sticking with the USB C charger that came with the Nexus 5X.

 

Thermal image of Max