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projects:crazyflie:firmware:log

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Crazyflie LOG subsystem

The purpose of the logging is to be able to log variables that are available in the copter during runtime. The Crazyflie log system is design in such a way that the copter firmware is mostly independant from the client and all information required to get the log system to work are communicated at connection time. The copter contains a table of content of all the variable possible to log. The client retrieve the list at connection time. The client then program in the copter log packets (ie. list of variable to log at the same time) to be sent back at regular interval.

This mechanism is used both for regular log operation (ie. user requested log to inspect and debug flight data) but also to update indication in the GUI application.

Each variable to log is contained in a

Communication protocol

The log port is separated in 3 channels:

Table of content access

This channel is used to access the loggable variables table of content.

The first byte of each messages correspond a command. All communication on this port are initated by the client and all answer from the copter will contain the same command byte.

TOC command byte Command Operation
0 GET_ITEM Get an item from the TOC
1 GET_INFO Get information about the TOC and the LOG subsystem implementation

Get TOC item

The GET_ITEM TOC command permits to retrieved the log variables name, group and types from the copter. This command is intended to be requested from all the ID from 0 to LOG_LEN (see GET_INFO).

Request (PC to Copter):
        +--------------+----+
        | GET_ITEM (0) | ID |
        +--------------+----+
Length         1         1

Answer (Copter to PC):
        +--------------+----+
        | GET_ITEM (0) | ID |                                        If index out of range
        +--------------+----+------+------------+--------------+
        | GET_ITEM (0) | ID | Type |   Group    |     Name     |     If returning Item
        +--------------+----+------+------------+--------------+
Length        1          1     1    < Null terminated strings >
Request fields Content
GET_ITEM At 0 for GET_ITEM operation
ID ID of the item to be retrieved. The variables are numbered from 0 to LOG_LEN (see GET_INFO command)
Answer fields Content
GET_ITEM 0 for GET_ITEM operation
ID ID of the item returned
Type Variable type of the element. See variable types list
Group Null-terminated string containing variable group
Name Null-terminated string containing the variable name

Type, group and name are not sent if the required ID is higher than TOC_LEN-1.

Get Info

The get info command is intended to be requested first when connecting to the copter. This permits to know the number of variable, the limitations of the log implementation and the fingerprint of the log variables.

Request (PC to Copter):
        +--------------+
        | GET_INFO (1) |
        +--------------+
Length         1

Answer (Copter to PC):
        +--------------+---------+---------+-----------------+-------------+
        | GET_INFO (1) | LOG_LEN | LOG_CRC |  LOG_MAX_PACKET | LOG_MAX_OPS |
        +--------------+---------+---------+-----------------+-------------+
Length        1             1         4             1               1
Request fields Content
GET_INFO At 1 for GET_INFO operation
Answer fields Content
GET_INFO 1 for GET_INFO operation
LOG_LEN Number of log items contained in the log table of content
LOG_CRC CRC values of the log TOC memory content. This is a fingerprint of the copter build that can be used to cache the TOC
LOG_MAX_PACKET Maximum number of log packets that can be programmed in the copter
LOG_MAX_OPS Maximum number of operation programmable in the copter. An operation is one log variable retrieval programming
projects/crazyflie/firmware/log.1349616653.txt.gz · Last modified: 2015-07-15 16:30 (external edit)