CAN BUS Shield V2 - Arduino Hardware setup and code

I recently bought a CAN BUS Shield V2.0 from Seed Studio. I need to implement receiving data via CAN BUS between a system and an Arduino Uno board. The Shield is connected to the system via a DB9 cable. However, the system is not working, and I have the following doubts:

  • Do I need to insert a 120 ohm resistor in series with the connection, or is there already an integrated resistor on the board by default? (I haven’t made any hardware modifications to the board).

  • Is the default CS pin D9?

  • How should I write a code that turns on an external LED (connected to, for example, pin D4) when the last element of the received CAN message is equal to 1?

Thank you very much in advance for your help.