Additions and Limitations

This chapter describes some of the ways that the Lua interpreter running on the OEM7 receiver is different than a standard Lua interpreter.

Additions

  • The mobdebug module is preloaded to facilitate debugging.

  • Help messages are available for some functions. Use the H() function within the receiver Lua prompt to view help.

  • The crc32 module was created by NovAtel to generate CRCs for NovAtel messages. Use H(crc32) on the receiver Lua prompt for more details.

  • The scom module was created by NovAtel as convenience functions to access the SCOM ports. Use H(scom) on the receiver Lua prompt for more details.

  • If a Lua script has been started with the LUA PROMPT command, it can be stopped using the os.exit() Lua command.

  • A 64 kB RAM disk has been provided to the Lua interpreter at the location /tmp.

  • The os.tmpname() function will return a unique file name within /tmp.

  • Some environment variables have been added to the Lua interpreter running on the OEM7 receiver. They can be accessed using the os.getenv() function and are defined as follows:

    • "ONTARGET" is set to "true".
    • "GPSCARD_PSN" is set to the receiver PSN.
    • "ENCLOSURE_PSN" is set to the receiver's enclosure PSN, if one is set.

Limitations

  • The C User Application is not available to customers. That is, customers cannot write C code or take external, compiled libraries and link them to the Lua interpreter running on the OEM7 receiver.

  • The Operating System Library is not fully-functioning.

    • os.time() and os.date() report in Greenwich Mean Time (GMT)
    • os.date() will report time starting from Jan 1 1970, until GPS coarse time is set, at which point it will report the current time.

  • There is no way to stop a Lua script that was started with LUA START, unless the script itself completes.

  • It is not recommended to use LUA for high rate logging. Expect latency of 50 ms or more.

  • Latency will increase when idle time is low.