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Configuration Settings

Configuration Database

All configuration settings for the GNSS receiver are stored in a database, which is organized by separate layers. At startup, the receiver reads all the Configuration Layers from the database to constructs the Current Configuration, which is stored in the RAM and used by the receiver at run-time. Any configuration in any layer is organized as Configuration Items, where each Configuration Item is referenced to by a unique Configuration Key ID and holds a single Configuration Value.

  • Configuration Data - The binary representation of a list of Key ID and Value pairs
  • Configuration Items - Consists of a (Configuration) Key ID and its (Configuration) Value
  • Configuration Layers - These layers store the Configuration Items
  • Current Configuration - The culmination of highers priority configuration items from all the configuration layers, which are used by the receiver at run-time. The Current Configuration is called the RAM layer.

Configuration database

A chart of the Configuration Layers and Configuration Items from the Configuration Database.

Configuration Layers

The receiver has several Configuration Layers, some of the layers are read-only while others are modifiable. The layers are organized in terms of priority. Values in a high-priority layer replace values stored in a low-priority layers. At startup, the receiver reads all Configuration Layers and stacks up the items to create the Current Configuration, which is used by the receiver at run-time.

The following Configuration Layers are available (in order of priority, highest priority first):

  1. RAM
    This layer contains items stored in volatile RAM. This is known as the Current Configuration. The value of any item can be set by the user at run-time (see [UBX protocol] interface) and it is effective immediately.
  2. BBR
    This layer contains items stored in the battery-backed RAM. The contents in this layer are preserved as long as a battery backup supply is provided during off periods. The value of any item can be set by the user at run-time (see UBX protocol interface) and it becomes effective when the receiver is restarted.
  3. Flash
    This layer contains items stored permanently in the external flash memory. This layer is only available if there is a usable external flash memory. The value of any item can be set by the user at run-time (see UBX protocol interface) and it becomes effective when the receiver is restarted.
  4. Default
    This layer contains all items known to the running receiver software and their hard-coded default values. Data in this layer is not writable.

UBX Protocol

The following UBX protocol messages are available to access the ***Configuration Database**:

  • UBX-CFG-VALGET: Read Configuration Items from the database
  • UBX-CFG-VALSET: Set Configuration Items in the database
  • UBX-CFG-VALDEL: Delete Configuration Items from the database

Configuration Reset

The RAM layer is always rebuilt from the Configuration Layers when the chip's processor comes out from reset. When using UBX-CFG-RST, the processor goes through a reset cycle with these reset types (resetMode field):

  • 0x00 hardware reset (watchdog) immediately
  • 0x01 controlled software reset
  • 0x04 hardware reset (watchdog) after shutdown

Common Configuration Groups

These are groups of specific Configuration Items that users will likely be interested in:

Group Description
CFG-HW Hardware configuration
CFG-I2C Configuration of the I2C interface
CFG-I2CINPROT Input protocol configuration of the I2C interface
CFG-I2COUTPROT Output protocol configuration of the I2C interface
CFG-MSGOUT Message output configuration
CFG-NMEA NMEA protocol configuration
CFG-RATE Navigation and measurement rate configuration
CFG-SPI Configuration of the SPI interface
CFG-SPIINPROT Input protocol configuration of the SPI interface
CFG-SPIOUTPROT Output protocol configuration of the SPI interface
CFG-TP Time pulse configuration
CFG-UART1 Configuration of the UART1 interface
CFG-UART1INPROT Input protocol configuration of the UART1 interface
CFG-UART1OUTPROT Output protocol configuration of the UART1 interface