Saturday, May 17, 2014

Making CAN bus

Part List

  • Soldering Iron: I had a cheap 30W iron that came together with RadioShack kit, it is worthless!
  • Buy quality soldering gun and make yourself a fine copper tip out of 12 gauge copper wire.
  • Wire 24 gauge; 20 feet - I did not find any standard for CAN bus colors, in fact I have seen the same manufacturer using different colors in different products.
  • 2x Resistors 120 Ohm (brown, red, brown)
  • several DB9 connectors both male and female so you have plenty of connection points to your CAN bus (sensors, Serial-to-USB, etc.)

When you you go thru dozens of resistors, it is much faster to find them by COLOR, then connecting to multimeter. 

Wiring s/n P397 USB to CAN dongle

Fortunately this part has pretty good documentation about how to wire it

  • PIN #2 white - CAN_L
  • PIN #7 green - CAN_H
  • PIN #1 not connected red - 3.3V DC
  • PIN #6 not connected black - ground

  • When you choose pins make sure you look at the MALE plug from user end, not wires end, they should be marked.

    Wiring iMX.6 board

    The iMX.6 MicroComputer has a 3 pin CAN bus socket that can be used with optional plug part featuring following cables:

    • brown
    • red
    • orange
    The i.MX6 Hardware Manual specifies the following:
    FlexCAN1 module is implementing full CAN specification 2.0b (11/29bit IDs @ 1Mb/s)

    • pin#: X2A4, Signal: X_CAN0_TXD, ST: O, transmit
    • pin#: X2A5, Signal: X_CAN0_RXD; ST: I, receive
    • pin#: X2A7, Signal: 3.3V reference voltage; 
    Unfortunately it does not tell the ORDER, or COLOR of the wires.
    I could not find anything online, so it will be a trial and error. I used an easy screw on connector just so it is easy to switch polarity.

    Here is an image of finished can bus:

    • connects to i.MX6 board
    • it runs over 2 pairs of green/white wire
    • ends with DB9 connectors (one male, one female)
    • it is terminated with DB9 connectors that have 120 Ohm resistors across pins 2 and 7