this might be a stupid question but i'm unable to clarify this by myself. So i'm working on a project with a STM32F429zit microcontroller. I would like to use CANopen in my project so i can communicate with other CANopen devices. From what i know now is that CANopen is a layer written on top of the CAN protocol. So it uses the same hardware. My microcontroller has 2 CAN interfaces, i've seen a video on youtube( https://www.youtube.com/watch?v=GYhsHJi6pKE&t=357s ) from a guy connecting two STM32F429 boards to each other via CAN directly. I've also seen a movie from a guy using three STM32F429 boards and connect them all together via CAN with a MCP2551 transceiver( https://www.youtube.com/watch?v=4fYoXGiIdDs ). Could somebody explain me the difference between those two setups? Is it really necessary to use an external transceiver to communicate over CAN? I'm planning to communicate with touchscreens using CANopen, those screens are working on 12VDC.
I hope somebody can clarify this for me.
Thank you all!!