Loopback on CAN bus - Apalis imx6, ixora v1.1, Linux

Technical Support
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1

Hello,

I want to do a loop back test on ixora v1.1 with can-utils.
Is it enough to simply connect can bus 0 and 1 to each other with a jumper? Do I need some kind of termination circuit?

thanks
rifo

2

Hi

While you violate the CAN specification this has always worked for me.

Max

3

Hello,

I connected the Can1_H <-> Can2_H, Can1_L <-> Can2_L
I then used cansend and candump but wasn’t able to receive anything.

root@apalis-imx6:~# cansend imp 18FF2488#01.FF.00.00            
interface = imp, family = 29, type = 3, proto = 1

root@apalis-imx6:~# candump tra
interface = tra, family = 29, type = 3, proto = 1
<0x001> [1] 12 

root@apalis-imx6:~# ifconfig

imp       Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  
          UP RUNNING NOARP  MTU:16  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:10 
          RX bytes:0 (0.0 B)  TX bytes:1 (1.0 B)
          Interrupt:37 

tra       Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  
          UP RUNNING NOARP  MTU:16  Metric:1
          RX packets:1 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:10 
          RX bytes:1 (1.0 B)  TX bytes:0 (0.0 B)
          Interrupt:36

I will try to add the termination resistors and see what happens. If you have any suggestions please feel free to comment.

4

seems like I used the cansend incorrectly, below combination works fine.

 cansend imp -i 0x18FF2488 0x01 0xFF 0x00 0x10
interface = imp, family = 29, type = 3, proto = 1


root@apalis-imx6:~# candump tra
interface = tra, family = 29, type = 3, proto = 1
<0x488> [4] 01 ff 00 10