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:

  • External GNSS Connectivity:
    • The SOM-301x module provides external interfaces such as mPCIe or I/O cables through which you can connect external GNSS devices.
  • Position Data Filling:
    • Developers can utilize the external GNSS device connected to the host to obtain more accurate position data. This data can be fetched from the external GNSS device and filled into the fields of V2X messages such as BSM or CAM.
  • RTCM Message Support:
    • If you wish to transmit data from an external GNSS device to the SOM-301x module for advanced positioning correction or related applications, the V2Xcast® SDK provides support for RTCM (Radio Technical Commission for Maritime Services) messages. This allows you to transmit RTCM messages generated by the external GNSS device to the SOM-301x module for position updates or other relevant operations.
  • The SOM-301x module provides external 1PPS (One Pulse Per Second) pins that are exposed in both the mPCIe interface (pin 49) and the I/O cable (pin 5) for synchronization purposes. However, it is important to follow the recommended guidelines to avoid potential issues such as back powering and latch-up.
  • To ensure proper operation and prevent any undesired effects, the external 1PPS signal should be fed to the SOM-301x module at least 20 milliseconds after the module has powered up. This delay allows for the stable initialization of the module’s internal components and reduces the risk of power-related issues.

By adhering to this recommendation, you can ensure the reliable and optimal performance of the SOM-301x module when utilizing external 1PPS synchronization signals.

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