topic Re: CAN bus issue for 200 meters cable in S12 / MagniV Microcontrollers

CAN bus issue for 200 meters cable

aaronlee — Thu, 05 Dec 2019 17:03:56 GMT

Hi,

We use 10 boards(S12ZVCA) to send CAN message every 10 seconds. And 1 board(S12ZVCA) to collect those CAN message.

It can work fine in 10 meters cable. But it is unstable in 200 meters cable. How to solve the issue? Do you have any recommend?

Slew rate: 4

Baud rate: 250kbps

Time segment 1: 4 (We will try "12" on next Monday)

Time segment 2: 1

RSJ: 1

Sample per bit: 3 samples

BR, Aaron

Re: CAN bus issue for 200 meters cable

lama — Fri, 06 Dec 2019 10:08:44 GMT

Hi,

The long transmission line has its own distributed parameters. They creates reactance which depends on frequency. Moreover, they deforms edges of signals.

So you can solve your issue:

Decrease bitrate

Do correct bitrate calculations including real propagation delays ( https://www.nxp.com/docs/en/application-note/AN1798.pdf )

Use wires with low R/L/C parameters.

Use some repeaters.

Wireless CAN

For this distance probably you could use RS485 and UART.

Best regards,

Ladislav

Re: CAN bus issue for 200 meters cable

aaronlee — Sun, 08 Dec 2019 09:25:03 GMT

Hi Ladislav,

Thanks for your reply.

We only change Time segment 1 from 4 to 12. It can work stable in 200 meters cable.

The parameter as follow:

Slew rate: 4
Baud rate: 250kbps
Time segment 1: 12
Time segment 2: 1
RSJ: 1
Sample per bit: 3 samples

BR, Aaron