Can-Bus Shield: Both terminal pins are connected

[nikolas.engelhard]

I am trying to work with the seeedstudio can-Bus Shield (v0.9b) and currently try to find out why I don’t get anything.
To find the correct pins in the sub-9 connector I played around with my Multimeter and found out that both Can-Pins are connected which is somehow strange since Can is based on the different potential on the pins. To be more precise: I inserted my two probes into the green Can-Connectors for CanH and CanL and got a resitance of about zero (nice beeps from the multimeter). I also got this when touching the top middle and right pins of the sub9 (If you turn the shield around it’s pretty easy to see which pins are connected to the green terminal).

Is my shield broken or have I made a mistake? Could someone repeat my experiment and tell me what you get?

// Update:
Today I used a better multimeter and got a resistance of 62Ohm between the Pins.

[cory.j.fowler]

@nikolas.engelhard

I am trying to work with the seeedstudio can-Bus Shield (v0.9b) and currently try to find out why I don’t get anything.
To find the correct pins in the sub-9 connector I played around with my Multimeter and found out that both Can-Pins are connected which is somehow strange since Can is based on the different potential on the pins. To be more precise: I inserted my two probes into the green Can-Connectors for CanH and CanL and got a resitance of about zero (nice beeps from the multimeter). I also got this when touching the top middle and right pins of the sub9 (If you turn the shield around it’s pretty easy to see which pins are connected to the green terminal).

That is interesting…

@nikolas.engelhard

Is my shield broken or have I made a mistake? Could someone repeat my experiment and tell me what you get?

I unfortunately do not have this shield, I made my own for my application.

@nikolas.engelhard

// Update:
Today I used a better multimeter and got a resistance of 62Ohm between the Pins.

That sounds correct according to the schematic… I’ve been updating the schematic and noticed the “termination” resistor is incorrectly labeled as 60 ohms… I was hoping it was just a print error that did not make it to the actual product. The termination resistor should be 120 ohms. I desire to replace all “CAN-BUS_shield” designs with a design that is not application specific to OBD-II interfacing. I am mostly referring to the non-standard “CAN” pin-out used on the DE9 connector. The shield should not terminated by default regardless of its intended application.

There should be a trace connecting two solder pads together somewhere on the CAN_L or CAN_H lines, cut that with a knife or something, that should open the termination.