Analog Discovery 2 and CAN

[Abdulmalik]

How can I make my AD2 analyze CAN signals? I tried to follow the "CAN" section of Logic Analyzer in the link: https://reference.digilentinc.com/learn/instrumentation/tutorials/ad2-logic-analyzer/start#can

but I'm not sure how to connect to the bus and what inputs to use. Any help is greatly appreciated.

Thanks

[JColvin]

Hi @Abdulmalik,

Once you choose what data pin you want to use, you can connect the corresponding wire on the AD2 to the data line of interest. If you have multiple CAN datalines you want to be able to view, you can choose to add an additional CAN channel and use a different data line than was used in the first CAN channel. 

Did that answer your question?

Thank you,
JColvin

[Abdulmalik]

Hi JColvin,

Thanks a lot for the insightful answer. However, I still need more specific clarification for my setup. My CAN bus is differential (CAN_L & CAN_H), so how can I connect the two line and be able to see CAN messages?

 Thanks,

Abdulmalik

[attila]

Hi @Abdulmalik

It is suffice to connect one CAN signal with series resistor for voltages which exceed 0V-3.3V range or use transceiver to adapt it to 0/3.3V logic.
The AD2 digital IOs have protection diodes toward GND and 3.3V https://reference.digilentinc.com/reference/instrumentation/analog-discovery-2/reference-manual#digital_io
The logic threshold of DIO inputs is at about 1.5V and 0.5V with the 5th device configuration.

[Abdulmalik]

Hello @attila,

Thanks for answering my question.

I want to mention that my CAN bus is a test bench where it consists of microcontrollers with a CAN shield on top of each one of them. The shield has SN65HVD230 CAN controller. The schematic can be found here: https://www.waveshare.com/w/upload/1/16/RS485_CAN_Schematic.pdf

Could you perhaps elaborate on what you mean by: 

12 hours ago, attila said:

It is suffice to connect one CAN signal with series resistor for voltages which exceed 0V-3.3V range

 

12 hours ago, attila said:

use transceiver to adapt it to 0/3.3V logic

I have an MCP2551 transceiver that is connected to the CAN bus. What should I use as input for the AD2? The Rdx pin? If so, do I need GND somewhere?

 

Thanks again

[kojak]

Hi @attila,

This is what I asked before. Do you think that will be possible to use only Rx and Tx from CAN/LIN transceiver in Logic or Protocol instrument in WaveForms? This should not be a problem as these transceivers are often a part of analyzed device, so it should be easy to connect directly to Rx/Tx. With protocol master mode this also enable great posibilites to control CAN/LIN buses.

On 10. 11. 2017 at 7:50 AM, kojak said:

Hi @attila

do you think that master mode in Protocol instrument will be possible without any CAN on LIN controller, only with CAN or LIN transceiver (eg. TJA1042 resp. TJA1027)?

 

[attila]

Hi @Abdulmalik

You should connect GND and RXD to AD2 GND and one DIO line.
Open Logic Analyzer in WaveForms, add CAN interpreter, select the connected DIO line and set Polarity to High Low.

[Abdulmalik]

Hi @attila,

Thank you very much!

I was missing to connect the AD2's GND. Once I did that, everything worked out perfectly

[attila]

Hi @Abdulmalik

Thank you for the confirmation.

[attila]

Hi @kojak

The CAN bus for Protocol interface is under development.

[kojak]

Hi @attila,

Great, will hope it will be soon done.

Thank you.

[kojak]

Hi @attila,

It looks like CAN protocol has been added into last version of WF, but it is not written in changelog. I did'n test it yet, but hope it is working.

Thank you

[usermacn]

On 12/7/2017 at 8:42 PM, Abdulmalik said:

Hi @attila,

Thank you very much!

I was missing to connect the AD2's GND. Once I did that, everything worked out perfectly

Hello, can you elaborate on how you got your system to work?