Fejemis bridge

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Bridge overview

The bridge combines different inputs from hardware sources to a single message database from which the messages can be seubscriber. This makes the bridge a combination of a bridge (slightly reformatting the messsages) and a message broker, from which clients can subscribe to messages. Messahes can also be send from any of these broker-clients.

Selected interface points are made available as ROS messages and key commands can be received from ROS.

The main input and output connections are to the Drive and Front Teensy boards, these connections are protected by a simple checksum, the ';99' part, to avoid false or half messages when powering up.

• All data items are single lines of text. These data items start with a key and optionally additional parameters. The data item has further a data source associated.
• Data items can be directed to a destination (data forward).
• A data item can be requested, or updates to a data item can be subscribed.

The ini-file holds a set of commands, e.g. calibration data or subscription of data to any destination.

All data items can be logged individually with a timestamp.

The client GUI is to help configure/calibrate the sensors and low-level control loops.

Bridge initialization file

The initialization file holds a list of commands that will be handled by the bridge. The file is called bridge.ini and is positioned in the same directory as the executable

Most commands start with a destination keyword. If that interface is opened after the initial read of the initialization file, then the file is read again for the commands destinated for this interface.

An example of an initialization file could be:

; inifile to fejemis bridge
; start both Teensy connections
bridge teensy 0 1
bridge teensy 1 1
; front teensy help
# Text from ini-loader
drive posei
drive veli
drive gyroi
drive confi
; subscribe to regular stream of data
drive sub pose 10
drive sub gyro 11
drive sub enc 9
drive sub bat 400
drive sub conf 801
drive sub hbt 601
drive sub mot 23
drive sub id 2000
drive sub ver 2001
; 
front led 1 200 0 0
front led 2 200 0 0
front led 3 200 0 0
front led 4 200 0 0
front led 5 200 0 0
front led 6 200 0 0
front sub id 2000
front sub ver 2001
front sub hbt 601
; max values for RC control 
; velocity (m/sec), turnrate deg/sec and slow factor (0.2'ish)
joy rcmax 2.0 45 0.2
;drive:pose logopen
;drive:gyro logopen
; allow robot to drive
;drive arm
; send RC to both front and drive
gamepad:rc subscribe -1 front
gamepad:rc subscribe -1 drive
gamepad:rc subscribe -1 regbot
; send steer angle to drive
front:fwl subscribe -1 drive
;
; command-line options
; if bridge is run from the command line
regbot:# subscribe -1 console
front:# subscribe -1 console
drive:# subscribe -1 console
;
; publish pose to ROS
; if source is a regbot
;regbot:pose subscribe -1 ros
; if source is fejemis
;drive:pose subscribe -1 ros

Lines starting with ';' is a comment

Management commands

Both data items and data sources can be managed by a set of reserved keywords. That is, if a command is sent to a destination with one of these keywords, the message is not sent to the data source, but handled by the interface.

Reserved commands for an interface

The reserved keywords or commands related to an interface:

Ini-file handler

A command line starting with the destination 'ini' is handled by the initialization module, e.g.:

ini reload drive

Command list:

* load <filename>         Load a specific initialization file (bridge.ini is always loaded at the start of the bridge).
* reload <interface name> Reloads the system initialization file (bridge.ini) for this interface.
* help                    This list

Teensy interface

e.g.:

drive logopen

Command list:

* meta      Get the metadata related to the interface, a text message.
* logopen   Create logfile with all updates through this data source.
* logclose  Close the logfile.
* help      This list

Bridge

e.g.:

bridge list

Command list:

* list         List all data items and data sources in the system as text
* items        List all data items in the format 'item N U L source: keyword params', where N is item number, U is number of updates received, L is logfile open.
* restart      Is a command to restart the bridge (and thereby delete all data points)
* quit         Quit the bridge
* batlow V     Set the battry low value to V (the system shuts down, when this value is passed).
* teensy D A   Starts or stops a teensy connection, D is device (0 or 1), set A=1 to activate or A=0 to deactivate.
* help         This list

Joystick (gamepad)

e.g.:

gamepad dev

Command list:

* dev           Lists gamepad interface details
* rcmax V T S   Set maximum velocity (m/s), turnrate (deg/sec) and slow factor ]0..1]
* spgm  B cmd   Associate a buttom B on the gamepad with a command 'cmd'
* help          This list

ROS interface

No specific commands.

Reserved commands for a data item

The reserved keywords handled by a data item are:

e.g.:

drive:pose subscribe -1 ROS

Command list:

* subscribe    E.g. 'drive:pose subscribe -1 ros', where the data item is 'pose' from the 
               source 'drive', the parameter -1 means all updates and the destination 
               interface is 'ROS'.
* onupdate P C Set a message to be handled, when this data item is updated, 
               e.g. request a gyro message, when an actuator is activated. 
               P=-1 all updates, 0=none, else interval in ms as fastest rate. C is the action string.
* status       Request status for the data item (number of updates, and list of subscribers).
* name string  Set the name of the data item, e.g. 'drive::conf name Configuration values 
               for drive system', anything after 'name ' is the new description of the data item.
* get          Get the latest value of the data item.
* meta         Get the metadata related to the data item (including the name).
* logopen      Create logfile with all updates to this data item or all traffic through this data source.
* logclose     Close the logfile.
* help         This list).