Run it, test it, use it

You can run the binding using afm-util tool, here is the classic way to go :

afm-util run canbus-service@4.0

The tool afm-util tool is automatically installed in the redpesk image. You can find documentation about Application Framework Binder

But you can’t control nor interact with it because you don’t know the security token that Application Framework gave it at launch.

So, to test it, it is better to launch the binding manually. In the following example, it will use port 1234 and leave empty the security token for testing purposes:

afb-binder --name=afbd-canbus-binding --workdir=/usr/local/canbus-binding --binding=lib/ --port=1234 --token=1 --tracereq=common -vvv

On another terminal, connect to the binding using previously installed AFB Websocket CLI tool:

afb-client -H ws://localhost:1234/api?token=1

You will be on an interactive session where you can communicate directly with the binding API.

The binding provides at this moment 2 verbs, subscribe and unsubscribe, which can take argument by a JSON event object.

The argument value is the CAN message generic_name as described in the JSON file used to generate cpp file for the binding.

To use the AFB Websocket CLI tool, a command line will be like the following:

<api> <verb> <arguments>


  • API : canbus.
  • Verb : subscribe or unsubscribe
  • Arguments : { “event”: “” }

Subscription and unsubscription

Signal (un)subscription

You can ask to subscribe to chosen CAN signal calling API and a verb with the name of the signal as verb prefixed by the plugin name holding the signal.

For example from an opened session:

canbus vcar/ "subscribe"
ON-REPLY 1:canbus/vcar/ {"jtype":"afb-reply","request":{"status":"success","uuid":"a18fd375-b6fa-4c0e-a1d4-9d3955975ae8"}}

Then you will receive an event each time a CAN message is decoded for the event named with its received timestamp if available:

ON-EVENT canbus/vcar/vcar\/{"event":"canbus\/vcar\/","data":{"vcar\/":true, "timestamp": 1505812906020023},"jtype":"afb-event"})

You can stop receiving events from it by unsubscribing the signal the same way you did for subscribe

canbus vcar/ "unsubscribe"
ON-REPLY 2:canbus/vcar/ {"jtype":"afb-reply","request":{"status":"success"}}

Message (un)subscription

You can also subscribe to an event with the ID or the PGN of the message definition :

canbus subscribe {"id" : 1568}
canbus subscribe {"pgn" : 61442}

And subscribe to all ID or PGN :

canbus subscribe {"id" : "*"}
canbus subscribe {"pgn" : "*"}

You can stop receiving events from it by unsubscribing the signal the same way you did for subscribing

canbus unsubscribe {"id" : "*"}
ON-REPLY 3:canbus/unsubscribe: {"jtype":"afb-reply","request":{"status":"success"}}
canbus unsubscribe {"pgn" : "*"}
ON-REPLY 4:canbus/unsubscribe: {"jtype":"afb-reply","request":{"status":"success"}}

Filtering capabilities

It is possible to limit received event notifications into minimum and maximum boundaries as well as doing frequency thinning. This is possible using the argument filter with one or more of the filters available :

  • frequency: specify in Hertz the frequency which will be used to get notified of new CAN events for the designated signal. If, during the blocked time, further changed CAN messages are received, the last valid one will be transferred after the lockout with an RX_CHANGED.
  • min: Minimum value that the decoded value needs to be above to get pushed to the subscribed client(s).
  • max: Maximum value that the decoded value needs to be below to get pushed to the subscribed client(s)
  • rx_id : For the ISO TP protocol, define the id of source to write a message
  • tx_id : For the ISO TP protocol, define the id of emitter to receive message

Order doesn’t matter neither the number of filters chosen, you can use one, two or all of them at once.

Usage examples :

canbus vcar/engine.speed { "subscribe": {"filter": { "frequency": 3, "min": 1250, "max": 3500}}}
canbus vcar/engine.load  {"subscribe": {"filter": { "min": 30, "max": 100}}}
canbus vcar/vehicle.speed  {"subscribe": {"filter": { "frequency": 2}}}
canbus subscribe {"id": 273, "filter": {"tx_id" : 562}}

Get last signal value

You can also ask for a particular signal value on one shot using get verb, like this:

canbus vcar/engine.speed "get"
ON-REPLY 1:canbus/vcar/engine.speed: {"response":[{"vcar\/engine.speed":0}],"jtype":"afb-reply","request":{"status":"success"}}

CAUTION Only one event can be requested.

List of current loaded signals

Also, if you want to know the supported CAN signals loaded by canbus, use verb list

canbus list
ON-REPLY 2:canbus/list: {"response":["vcar\/","vcar\/hvac.temperature.left","vcar\/hvac.temperature.right","vcar\/hvac.temperature.average","vcar\/engine.speed","vcar\/fuel.level.low","vcar\/fuel.level","vcar\/vehicle.average.speed","vcar\/engine.oil.temp","vcar\/engine.oil.temp.high","vcar\/","vcar\/","vcar\/","vcar\/","vcar\/","vcar\/","vcar\/","vcar\/","vcar\/","vcar\/engine.load","vcar\/engine.coolant.temperature","vcar\/fuel.pressure","vcar\/intake.manifold.pressure","vcar\/engine.speed","vcar\/vehicle.speed","vcar\/intake.air.temperature","vcar\/mass.airflow","vcar\/throttle.position","vcar\/running.time","vcar\/EGR.error","vcar\/fuel.level","vcar\/barometric.pressure","vcar\/ambient.air.temperature","vcar\/commanded.throttle.position","vcar\/ethanol.fuel.percentage","vcar\/accelerator.pedal.position","vcar\/","vcar\/engine.oil.temperature","vcar\/engine.fuel.rate","vcar\/engine.torque"],"jtype":"afb-reply","request":{"status":"success","uuid":"32df712a-c7fa-4d58-b70b-06a87f03566b"}}

Write on CAN buses

Two modes could be used for that which is either specifying the CAN bus and a RAW CAN message either by specifying a defined signal, case-insensitively, and its value.


# Authentication
canbus auth
# Write a raw can frame to the CAN id 0x620
canbus write { "bus_name": "hs", "frame": { "can_id": 1568, "can_dlc": 8, "can_data": [ 255, 255, 255, 255, 255, 255, 255, 255]} }
# Write a signal's value.
canbus write { "signal_name": "engine.speed", "signal_value": 1256}
# Write J1939 'single frame'
canbus write { "bus_name": "j1939", "frame": { "pgn": 61442, "length":8, "data": [ 255, 255, 255, 255, 255, 255, 255, 255]} }
# Write J1939 'multi frame'
canbus write { "bus_name": "j1939", "frame": { "pgn": 61442, "length":9, "data": [ 255, 255, 255, 255, 255, 255, 255, 255, 254]} }
# Write ISOTP 'single frame'
canbus write {"bus_name": "hs", "filter": {"rx_id" : 562}, "frame": { "can_id": 273, "can_dlc": 8, "can_data": [ 255, 255, 255, 255, 255, 255, 255, 255]} }
# Write ISOTP 'multi frame'
canbus write {"bus_name": "hs", "filter": {"rx_id" : 562}, "frame": { "can_id": 273, "can_dlc": 9, "can_data": [ 255, 255, 255, 255, 255, 255, 255, 255, 25]} }

To be able to use write capability, you need to add the permission urn:redpesk:permission::platform:can:write to your package configuration file that needs to write on CAN bus through canbus api.

Then in order to write on bus, your app needs to call verb auth before calling write, to raise its LOA, Level Of Assurance, which controls usage of verb write.

Using signal dedicated verbs

The same as when you subscribe or unsubscribe for a signal you can use a dedicated verb to write on it if the signal has been set as writable:

canbus auth
canbus vcar/engine_speed { "write": 1256 }

Using CAN utils to monitor CAN activity

You can watch CAN traffic and send custom CAN messages using can-utils preinstalled on redpesk@ targets.

To watch watch going on a CAN bus use:

candump can0

Or for a USB CAN adapter connected to porter board:

candump can1

Send a custom message:


You can also replay previously dumped CAN logfiles. These logfiles can be found in can_samples directory under Git repository. The following examples use a real trip from an Auris Toyota car.

Trace has been recorded from a CAN device can0 so you have to map it to the correct one you use for your tests.

Replay on a virtual CAN device vcan0:

canplayer -I trip_test_with_obd2_vehicle_speed_requests vcan0=can0

Replay on a CAN device can0:

canplayer -I trip_test_with_obd2_vehicle_speed_requests can0

Replay on a CAN device can1 (porter by example):

canplayer -I trip_test_with_obd2_vehicle_speed_requests can1=can0