MEWS: Marine Electronics Wiki

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====== CAN Interfaces ======

USB CAN adapters can appear as follows on Linux.

===== SocketCAN =====

A can network device appears. e.g. can0, shown by ifconfig.

Set bitrate for NMEA2000 and bring up CAN interface:

''ip link set can0 up type can bitrate 250000''

It seems SignalK doesn't do this itself.

[[https://www.kernel.org/doc/html/v5.11/networking/can.html|Kernel SocketCAN docs]]  

===== Serial Line CAN =====

Some USB to CAN adapters may run a firmware that presents as a CDC-ACM serial port, e.g. CANable devices. **slcand** can talk to the devices over the virtual serial port and create a standard SocketCAN device, at which point you can continue the same as with a native SocketCAN adapter.

''slcand -o -s5 /dev/ttyACMx''

The -s arguments sets the CAN bus speed:
<file>
    -s0 = 10k
    -s1 = 20k
    -s2 = 50k
    -s3 = 100k
    -s4 = 125k
    -s5 = 250k
    -s6 = 500k
    -s7 = 750k
    -s8 = 1M
</file>

===== Analysers =====

==== Canboat ====

Install Linux SocketCAN tools:
''sudo apt install can-utils''

Configure SocketCAN interface:
''ip link set can0 up type can bitrate 250000''

Use canboat analyzer tool:
''candump can0 | candump2analyzer | analyzer''

==== Wireshark ====

Can open SocketCAN interfaces, like ''can0''. Select ''Analyze -> Decode As'', and in the last column of the table you can click to set it to ''J1939''. This will decode as far as giving you PGNs. I didn't find an NMEA2000 decoder, but this at least tells you data is flowing.

===== Hardware =====

==== CANable ====

CANable is a USB - CAN interface using an STM32F072. CANable firmware does slcan. The same device can be flashed with candleLight firmware which does Linux native / SocketCAN. I bought a device from Aliexpress which came with candleLight.

[[https://www.aliexpress.com/item/1005006032351087.html]]

==== Waveshare Pico CAN ====

[[waveshare_pico_can|Waveshare Pico CAN]]

==== NMEA2000 - USB Interface ====

[[ngt-1|Actisense NGT-1]]