not really an issue but ... use S88 galvanic isolation

[GBert]

please have a look at :
https://github.com/GBert/misc/raw/master/BPi-CAN/BPi-CAN_sch_1.pdf

at button left . It will also protect your RPi against overvolatge and power glitches on the S88 bus.

[hthiery]

ok sounds like a good idea!

what about using quad opto coupler ... e.g. LTV 847

[GBert]

Sorry wrong sheet: it's https://github.com/GBert/misc/raw/master/BPi-CAN/BPi-CAN-v1.0.pdf
From the RPi perspective GPIO4 (Data) is input, the others (RESET, LOAD & CLOCK) are output.
I use 6N137 because they are fast and cheap.

The U6 circuit (input pin at 3V3) was simulated because 6N137 normally uses 5V. simulation was fine