Re: free CAN troubleshooting sheet

Hi John,

Thanks for your messages & feedback.

I’ll consider improvements to the sheet to emphasize the importance of the reference point. I already have the GND symbol there, but maybe I’ll add a note as well.

In regards to the scope traces, I’ve decided to leave it out because I feel most of the CAN wiring issues can be solved with a multimeter alone. Also, because I found many service techs do not have a scope available in my industry (heavy machinery).

The positive side is that even when a scope is not available, one could use a multimeter to make some inferences about the CAN signals: the average DC voltage reading of CANH and L, with respect to ground, should fall within a certain envelope. If readings are outside that envelope likely something is not right. Fortunately this test us on the sheet under “Voltage Test”

Regards,
Igor Ramos

to recap, the troubleshooting sheet can be found here: http://canbusacademy.com/can-bus-troubleshooting-pdf-sheet/




On Aug 5, 2014, at 5:44 PM, John Dammeyer <[email protected]> wrote:

> Hi Igor,
> I’d try an squeeze in a couple of scope photos or sketches that show what the bus looks like with a reminder that CAN is a 2 wire + ground system. 
> I watched someone try and diagnose an RS485 system the other day (which can operate without the ground) but they put the scope ground on one of the RS485 lines and the probe on the other.   For some reason the signals looked good but the PLC wasn’t receiving the messages. 
> When it was my turn the first thing I did was move the scope leads around so the ground was where it should be and the two scope probes were on the RS485 +/- leads.  Now we suddenly saw that the PLC wasn’t configured for bi-directional RS485 (2 wire) and so stayed in transmit drive mode.
> What I’m trying to say is there is a world of diagnostic information available from just a quick peak at the scope on the bus.
> John Dammeyer
>  
> From: [email protected] [mailto:[email protected]] On Behalf Of Igor Ramos
> Sent: August-05-14 2:54 PM
> To: [email protected]
> Subject: Re: [CANLIST] free CAN troubleshooting sheet
>  
> I’m new to the list as well. I’m the author of the CAN troubleshooting sheet below. I created based on my 10+ years of experience designing CAN systems. Even though there’s just so much content you can put in one sheet, those are my typical steps when troubleshooting a CAN system.  
>  
> What steps/instructions would you add or remove from that sheet?
>  
> Regards,
> Igor Ramos
> CANbusAcademy.com
>  
>  
> On Aug 5, 2014, at 4:38 PM, Al Thomason <[email protected]> wrote:
> 
> 
> Um…  I am new to this list, but I hope the following is not typical – I found it to be totally lacking  content and really just a way to harvest Email addresses.
>  
> -al-
>  
>  
>  
> From: [email protected] [mailto:[email protected]] On Behalf Of Igor Ramos
> Sent: Tuesday, August 05, 2014 8:07 AM
> To: [email protected]
> Subject: [CANLIST] free CAN troubleshooting sheet
>  
> Check out this CAN Troubleshooting Quick Reference sheet. It contains some key test procedures to troubleshoot a CAN bus using a multimeter. Let me know if you like it.
>  
> http://canbusacademy.com/can-bus-troubleshooting-pdf-sheet/