3. Any option to use external GNSS in addition to the onboard GNSS of SOM-301x ?

SOM is a very flexible off-the-shelf V2X system-on-module to support the use of external GNSS, in addition to the onboard GNSS.

As the onboard GNSS is a major component in the Unex’s V2X system, it will serve to provide “position” and “timing” for both V2X protocol stacks and V2X applications. The illustrated application is as below:

GNSS will serve to provide “position” and “timing” for both V2X protocol stacks and V2X applications
  • The fields of messages (e.g. BSM or CAM) are filled by app. developers, so the position data could be fetched from GNSS devices connected to your host and filled by yourself.
  • It is similar in the reversed way. The data in the messages (e.g. RTCM) could be fed into GNSS devices connected to your host by yourself.
  • The pre-integrated GNSS is served for V2X protocol stacks to make all the functions work correctly.

Remarks:

external 1PPS pins are exposed in both mPCIe interface pin 49 and I/O cable pin 5. To avoid back powering and latch-up, external 1PPS should be fed to SOM-301 at least 20ms later than SOM-301 power up.
use external GNSS in addition to the onboard GNSS of SOM