Information About The Log; Recording - Ublox RCB-F9T Integration Manual

processed. The logging system will start up automatically on power-up if there is a log in existence.
The log will remain in the receiver until specifically erased using the UBX-LOG-ERASE message.
The CFG-LOGFILTER-* configuration group controls whether logging of entries is currently enabled
and selects position fix messages for logging.
Figure 7: The top level active/inactive states of the logging subsystem

3.4.3 Information about the log

The receiver can be polled for a UBX-LOG-INFO message which will give information about the log.
This will include the maximum size that the log can grow to (which, due to overheads, will be smaller
than that requested in UBX-LOG-CREATE) and the amount of log space currently occupied. It will
also report the number of entries currently in the log together with the time and date of the newest
and oldest messages that have a valid time stamp.
Log entries are compressed and have housekeeping information associated with them, so the actual
space occupied by log messages may be difficult to predict. The minimum size for a position fix entry
is 9 bytes and the maximum 24 bytes, the typical size is 10 or 11 bytes. If the odometer is enabled
then this will use at least another three bytes per fix.
Each log also has a fixed overhead which is dependent on the log type. The approximate size of this
overhead is shown in the following table.
Log type
circular
non-circular
Table 16: Log overhead size
The number of entries that can be logged in any given flash size can be estimated as follows:
Approx. number of entries = (flash size available for logging - log overhead)/typical entry size
For example, if 1500 kB of flash is available for logging (after other flash usage such as the firmware
image is taken into account) a non-circular log would be able to contain approximately 139000
entries: ((1500*1024)- (8*1024))/11 = 138891.

3.4.4 Recording

The CFG-LOGFILTER-RECORD_ENA configuration item must be set to true to enable recording into
the log. Nothing will be recorded if recording is disabled, otherwise position fix and UBX-LOG_STRING
entries can be recorded. When recording is enabled an entry will also be created from each UBX-LOG-
STRING message. These will be timestamped if the receiver has current knowledge of time.
The CFG-LOGFILTER-* configuration group has several values which can be used to select position
fix entries for logging. If CFG-LOGFILTER-APPLY_ALL_FILTERS is false , then all position fixes will
be logged (subject to a maximum rate of 1 Hz). Otherwise, a position is logged if any of the or if
UBX-22004121 - R01
C1-Public
Overhead
Up to 40 kB
Up to 8 kB
3 Receiver functionality
Early production information
RCB-F9T - Integration manual
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