u-blox ZED-F9P Interface Description - Manual
Advance Information
6 CFG Interface
This chapter describes the Receiver Configuration Database accessible thorough the Configuration Interface.
6.1 Configuration Database
The configuration database in the receiver's RAM holds the current configuration, which is used by the receiver
at run-time. It is constructed on startup of the receiver from several sources of configuration. These sources are
called Configuration Layers. The current configuration is called the RAM Layer. Any configuration in any layer is
organised as Configuration Items, which are referenced by a unique Configuration Key ID and hold a single
Configuration Value.
6.2 Configuration Items
The following figure shows the structure of a Configuration Item, which consists of a (Configuration) Key ID
and its (Configuration) Value:
A Configuration Key ID is a 32 bits integer value, which is split into three parts (Note that bits 31, 27..24 and
15..8 are reserved for future use and are currently unused.):
• bits 30..28: 3 bits that indicate the storage size of a Configuration Value (range 0x01-0x05, see below)
• bits 23..16: 8 bits that define a unique group ID (range 0x01-0xfe)
• bits 7..0: 8 bits that define a unique item ID within a group (range 0x01-0xfe)
The entire 32 bits value is the unique Key ID, which uniquely identifies a particular item. The numeric
representation of the ID uses the lower-case hexadecimal format, such as 0x20c400a1. An easier, more
readable text representation uses the form CFG-GROUP-ITEM. This is also referred to as the (Configuration) Key
Name.
The storage size identifiers (bits 30..28 of the Key ID) are:
• 0x01: one bit (the actual storage used is one byte, but only the least significant bit is used)
• 0x02: one byte
• 0x03: two bytes
• 0x04: four bytes
• 0x05: eight bytes
Each Configuration Item is of a certain type, which defines the interpretation of the raw binary data (see also
number formats):
• U1, U2, U4, U8: unsigned little-endian integers of 8-, 16-, 32- and 64-bit widths
• I1, I2, I4, I8: signed little-endian, two's complement integers of 8-, 16-, 32- and 64-bit widths
• R4, R8: IEEE754 single (32-bit) and double (64-bit) precision floats
• E1, E2, E4: unsigned little-endian enumeration of 8-, 16-, and 32-bit widths (like U1, U2 and U4)
• X1, X2, X4, X8: unsigned little-endian integers of 8-, 16-, 32- and 64-bit widths for bitfields and other binary
data, such as strings
UBX-18010854 - R04 Advance Information Page 189 of 259
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