Hi, Manuel,
Regarding your question about the CAN transceiver setting, I think this is the configuration for TWR-SER board.
1)you can connect the CAN differential signal to the pin1&3 of J7, pin1 is CANH,pin3 is CANL.
2)regarding the J6 jumper setting, pls close pin1&2, pin 5&6, pin7&8,pin9&10, OPEN 3&4. In the above setting the U4 CAN transceiver woks normally.
For the TWR-K70 board, you should populate the R22 and R33 with low resistors, you should use the CAN1 module, in other words, use the PTC16 as CAN1_RX and PTC17 as CAN1_TX.
Hope it can help you.
BR
Xiangjun Rong