CANedge2 Docs, Release FW 01.04.02
0.4.2.2 Configuration explained
This section contains additional information and examples.
File split
File splitting can be based on file size or file size and time:
•
split_time_period = 0
: Split based on size only
•
split_time_period > 0
: Split based on both size and time - whichever is reached first
Limits
The file system limits should be considered when configuring the split size and time:
• SD-card size
• Max
1024
sessions
• Max
256
splits (log files) in each session
Above limits result in a maximum of
1024*256=262144
log files if fully utilised.
If the session count limit is reached, the logger will either:
• Stop logging if cyclic logging is disabled
• Delete the oldest session if cyclic logging is enabled
If SD-card becomes full (no more space), the logger will either:
• Stop logging if cyclic logging is disabled
1
• Delete the oldest split file from the oldest session if cyclic logging is enabled
Compression
Log files can be compressed on the device during logging using a variant of the LZSS algorithm based on
. Compressed files will have
*.MFC
as file extension. A high window size improves compression
rates, but may cause message loss on very busy networks.
The table below lists results for J1939 and OBD data with different window size configurations
Window size (Bits) Data
J1939 % (range)
OBD % (range)
8
49.7 (47.1-51.4)
32.0 (30.3-32.8)
9
49.5 (46.3-51.6)
30.2 (29.6-31.1)
10
41.4 (38.9-45.5)
30.0 (29.6-30.8)
Decompression can be done using an implementation of LZSS or via the CANedge tools (see the CANedge
Intro).
Note:
The split size set in
split_size
considers the size of the compressed data. I.e. if the split size
is 10 MB, the resulting file sizes become 10 MB regardless if compression is used or not.
1
If files are offloaded through WiFi in the case of the CANedge2, the logging will resume
3
Compressed size in percentage of original. Lower is better.
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