Wiring CAN bus physically

General topics and discussions about the VESC and its development.
koenaad
Posts: 2
Joined: 20 Oct 2017, 14:10

Wiring CAN bus physically

Postby koenaad » 20 Oct 2017, 19:46

Hey everyone,

I was able to find various threads about using CAN to communicate between VESCs and/or other microcontrollers. But I couldn't find a single thread detailing how to actually connect these devices...

CAN uses differing topologies and termination resistors depending on the speed [wikipedia]:

  • High speed CAN: linear bus terminated with 120 Ω at each end of the bus (up to 1 MBit/s)
  • Low speed / fault tolerant CAN: linear and/or star bus with an overall termination resistance of about 100 Ω (up to 125 kBit/s)
The VESC has 500 kbaud CAN, so this would be high speed CAN I assume?

So I wonder:

  • Does the VESC have termination resistors built-in or should I provide some? This is not clear from the schematic (what does NI stand for?).
  • Is it possible to increase the CAN bus speed to 1 MBit/s?
I will be using 4 VESC v4.12.

Thanks!

pf26
Posts: 293
Joined: 28 Mar 2016, 14:37
Location: FR Valence

Re: Wiring CAN bus physically

Postby pf26 » 22 Oct 2017, 17:15

NI: not implemented ?
if you have 4 VESCs, you only need these terminaison resistors at both ends of the bus.
500kHz is already pretty fast for motor control application. At this speed, a CAN frame requires much less then a millisecond..
Going for higher CAN speed is possible but requires firmware change.

koenaad
Posts: 2
Joined: 20 Oct 2017, 14:10

Re: Wiring CAN bus physically

Postby koenaad » 24 Oct 2017, 08:40

I contacted DIY Electric Skateboard (where I ordered the VESCs) and they told me the CAN termination resistors are already included by them. So I'll simply remove two of them.

Thanks for the help!


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