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Introduction

CAN-logger is a real-time CAN bus monitor.

This application reads CAN frames from a data bus, decodes their payload and plots data in real-time.

How it works

  1. we access CAN bus via SocketCAN (using FFI from fsocket library)
  2. we use a simple configuration file to describe the structure of a CAN frame payload
  3. we send decoded data to a monitor written with CLX

How to build

  1. Ensure ASDF finds all 3 dependencies (:fsocket :clx and :unix-opts)
  2. Go to the directory with sources and execute make

How to test

  1. To simulate a CAN bus, use a virtual CAN interface.
  2. Optionally, create your own configuration file (example) and generate mock-up CAN data with this script.
  3. Build and start the application:
make; ./can-logger -p ./demo-config -c vcan0 -s 100 -w 60
  1. Generate CAN traffic with cangen-script
sh ./tests/cangen-script.sh
  1. Ensure you see on the monitor the data specified in the configuration file.

How to use

First, create a simple configuration file that describes how CAN data must be interpreted. For example, with this entry

can_id = {385}
signal = {analog}
byte_swap = {true}
data_type_mask = {i16, i16, i16, i16}
bit_factor_mask = {610.4e-9, 610.4e-9, 610.4e-9, 610.4e-9}
physical_factor_mask = {101.1, 0, 12.5, 300}
physical_offset_mask = {-50.0, 0, -100.0, -750.0}
label = {Pressure_inlet, None, Mass_flow_rate, Temperature}

you say that if the CAN-logger receives a frame like 385 # DE 0D A0 04 E7 00 EE 01, it should be decoded as follows:

  • signal type is analog, i.e. values in the payload are integers. Another option herer would be a digital signal type, where one encodes just 0s and 1s.
  • byte_swap is true means that the little endian format is used
  • data type mask is 4 x i16, that means we expect 4 16-bit signed integers decoded in the payload. One can choose between (i)signed and (u)unsigned 8/16/32-bit integers.
  • bit factors (b), physical factors (f) and physical offset (o) tell you how to convert the raw interger value to a physical unit (p): p = b*f + o
  • labels are tags for these units

Then provide the path to your config file as well as other arguments via CL

./can-logger -p "path-to-config-file" -c "name-of-can-interface" -s "sampling-time-in-milliseconds" -w "time-window-width-in-seconds"

For example:

./can-logger -p ./config -c vcan0 -s 100 -w 60

Tested

Red Hat 4.8.5-44 - SBCL 2.1.9

Requirements

  1. Linux kernel > 2.6.25
  2. Libraries:

Todos

  • Decode multiplexed payload

Acknowledgement

Kudos to Oliver Hartkopp for his brilliant work on the SocketCAN API!