Using Seeed Can Shield 2.0 + Seeeduino 4.2 for SSM Can Bus Communication

Hi Everyone,

I’m new here, and super new to arduinos. I kinda dove off the deep side of things, and have a really basic question to start with.

The setup:
2015 WRX Subaru (can bus equipped)
Seeeduino 4.2
Seeed Can Shield 2.0
Telemetry system (can bus equipped)

The goal is to have the seeeduino sit between the car’s ecu and my telemetry system. Subaru’s have a diagnostic protocol that can provide a lot of VERY interesting data. Old version of the car had diagnostic of OBDII kline. Newer ecu’s can allow diagnostic queries via can bus, making the amount of queries and replies much higher!

I found this project:

Which basically achieve the same goal as what I’d like to do, however I’d like to use the can bus system and not the ODBII k line. Gather a bunch of data from SSM with the seeeduino then transmit that back to the telemetry system via can.

I purchased the seeed can shield, and I want to know if I can connect to the car via the db9 pin, then also use the can H/L jumpers to connect to my telemetry system. Or is it only one at a time? I’m not entirely sure if I need two can shields or not.