# Connecting Can Bus Debugger with Arduino Uno

I'm currently trying to interface USB Peak Can with Spark fun can bus shield.

So I'm trying to test sending data from the Shield to the USB Peak Can bus, but nothing is sent at all, the same for receiving.

Here is the pin diagram for Peak USB Can Pin assignment D-Sub

Pin Pin assignment

1   Not connected / optional +5V
2   CAN-L
3   GND
4   Not connected
5   Not connected
6   GND
7   CAN-H
8   Not connected
9   Not connected / optional +5V


CAN-L, CAN-H are connected to the shield CANL, CANH, plus the ground common.

I'm not sure If I should add a terminal resistor, but if it's necessary, how would I connect, can I have a schematic diagram please ?

CAN is a 60Ohms Impedance both sides/ends terminated Bus (120Ohm resistors) At least that's the most common physical Layer approach.

borrowed from Wikipedia:

Wikipedia on CAN

This one - in the wikipedias linklist - has some nice descriptions

https://web.archive.org/web/20161213185005/http://inst.cs.berkeley.edu/~ee249/fa08/Lectures/handout_canbus2.pdf

This has some useful info on the common connectors.

http://www.interfacebus.com/Can_Bus_Connector_Pinout.html

I also always forced my superiors to buy galvanic isolated CAN sniffers like that

https://www.kvaser.com/product/kvaser-leaf-pro-hs-v2/

or stuff from vector informatik (used to sell brand labelled Kvaser a lot...)

You will have much less problems with levels, GND's etc... they just work in most cases

Edit01:

So at first sight, it seems the Adurino shield can be configured to standard sub-D layout plus already is terminated (guess the "wrong" value of 100 is to get it also work with OBD-II)

The USB Peak Can also supports the standard Layout

So thats fine, and last

The USB Peak Can also has an option for termination, but I would just solder a 120 Ohm resistor + a switch to pins 2 and 7 of the Adurino shields sub-D connector. So you can turn it on an off as needed

• So you think the problem is just a missing terminator resistor ? – andre Sep 18 '20 at 19:34
• without it won't work in any case – schnedan Sep 18 '20 at 19:35
• Thanks so much, I'm a noob, can you show me a 2 DB Connector from Arduino Shield to USB Peak Can which shows terminal resistor connection ? – andre Sep 18 '20 at 19:37
• I can try... you have some links? – schnedan Sep 18 '20 at 19:47
• an old man is no high speed train – schnedan Sep 18 '20 at 20:33