> For the complete documentation index, see [llms.txt](https://docs.macchina.cc/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.macchina.cc/projects/p1-projects/loopback-testing.md).

# P1 CAN Loopback

Send a CAN frame on CAN0 and receive it on CAN1, and vice versa, but this time with P1!

#### Items Used

* 1x [P1](https://www.macchina.cc/catalog/p1-boards/p1-under-dash)
* 1x [OBD3way board](https://www.macchina.cc/catalog/tools/obd3way)
* 1x 12V power supply

#### OBD3way Setup

CAN0H to CAN1H and CAN0L to CAN1L and place a termination resistor across these connections; see photos below for setup. 

![](https://1875989339-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-Lhg5aaQ-eiSLOcDoH85%2F-MAXDUC72SswDnad1yw5%2F-MAXIu_6aYjLrnGBrEKH%2FIMG_7207.JPG?alt=media\&token=e8810d18-7b83-4ea2-b2d3-83d31f9bff11)

![](https://1875989339-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-Lhg5aaQ-eiSLOcDoH85%2F-MAXDUC72SswDnad1yw5%2F-MAXJ0QKUg-3gM8MdAL4%2FIMG_7209.JPG?alt=media\&token=cb3458ed-b5bd-491e-9cf1-31013037fcb9)

#### Test

Once everything is hooked up, we power up P1, and SSH into P1 in two windows at: 192.168.7.2 to control each CAN channel at the same time. 

![](https://1875989339-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-Lhg5aaQ-eiSLOcDoH85%2F-M2nnxVMCHogtlfl9GS4%2F-M2nt2kcKHvosmgl3PF7%2Floopback.png?alt=media\&token=04cc113f-07e1-46f8-b88a-d90148b948a8)

Below you can see each session. Note that you'll want to send the "candump ..." command before sending the "cansend ..." command in the other window. 

{% tabs %}
{% tab title="CAN0 Terminal" %}

```
login as: debian
Pre-authentication banner message from server:
| Debian GNU/Linux 9
|
| BeagleBoard.org Debian Image 2019-08-03
|
| Support/FAQ: http://elinux.org/Beagleboard:BeagleBoneBlack_Debian
|
| default username:password is [debian:temppwd]
|
End of banner message from server
debian@192.168.7.2's password:

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
debian@beaglebone:~$ sudo ip link set can0 type can bitrate 250000
[sudo] password for debian:
debian@beaglebone:~$ sudo ifconfig can0 up
debian@beaglebone:~$ candump can0
  can0  01A   [8]  11 22 33 44 AA BB CC DD
  can0  01A   [8]  11 22 33 44 AA BB CC DD
  can0  01A   [8]  11 22 33 44 AA BB CC DD
  can0  01A   [8]  11 22 33 44 AA BB CC DD
  can0  01A   [8]  11 22 33 44 AA BB CC DD
  can0  01A   [8]  11 22 33 44 AA BB CC DD
  can0  01A   [8]  11 22 33 44 AA BB CC DD
  can0  01A   [8]  11 22 33 44 AA BB CC DD
  can0  01A   [8]  11 22 33 44 AA BB CC DD
  can0  01A   [8]  11 22 33 44 AA BB CC DD
  can0  01A   [8]  11 22 33 44 AA BB CC DD
  can0  01A   [8]  11 22 33 44 AA BB CC DD
^Cdebian@beaglebone:~cansend can0 01a#11223344AABBCCDD
debian@beaglebone:~$ cansend can0 01a#11223344AABBCCDD
debian@beaglebone:~$ cansend can0 01a#11223344AABBCCDD
debian@beaglebone:~$ cansend can0 01a#11223344AABBCCDD
debian@beaglebone:~$ cansend can0 01a#11223344AABBCCDD
debian@beaglebone:~$ cansend can0 01a#11223344AABBCCDD
debian@beaglebone:~$ cansend can0 01a#11223344AABBCCDD
debian@beaglebone:~$ cansend can0 01a#11223344AABBCCDD
debian@beaglebone:~$ cansend can0 01a#11223344AABBCCDD
debian@beaglebone:~$ cansend can0 01a#11223344AABBCCDD
debian@beaglebone:~$
```

{% endtab %}

{% tab title="CAN1 Terminal" %}

```
login as: debian
Pre-authentication banner message from server:
| Debian GNU/Linux 9
|
| BeagleBoard.org Debian Image 2019-08-03
|
| Support/FAQ: http://elinux.org/Beagleboard:BeagleBoneBlack_Debian
|
| default username:password is [debian:temppwd]
|
End of banner message from server
debian@192.168.7.2's password:

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
debian@beaglebone:~$ sudo ip link set can1 type can bitrate 250000
[sudo] password for debian:
debian@beaglebone:~$ sudo ifconfig can1 up
debian@beaglebone:~$ cansend can1 01a#11223344AABBCCDD
debian@beaglebone:~$ cansend can1 01a#11223344AABBCCDD
debian@beaglebone:~$ cansend can1 01a#11223344AABBCCDD
debian@beaglebone:~$ cansend can1 01a#11223344AABBCCDD
debian@beaglebone:~$ cansend can1 01a#11223344AABBCCDD
debian@beaglebone:~$ cansend can1 01a#11223344AABBCCDD
debian@beaglebone:~$ cansend can1 01a#11223344AABBCCDD
debian@beaglebone:~$ cansend can1 01a#11223344AABBCCDD
debian@beaglebone:~$ cansend can1 01a#11223344AABBCCDD
debian@beaglebone:~$ cansend can1 01a#11223344AABBCCDD
debian@beaglebone:~$ cansend can1 01a#11223344AABBCCDD
debian@beaglebone:~$ cansend can1 01a#11223344AABBCCDD
debian@beaglebone:~$ candump can1
  can1  01A   [8]  11 22 33 44 AA BB CC DD
  can1  01A   [8]  11 22 33 44 AA BB CC DD
  can1  01A   [8]  11 22 33 44 AA BB CC DD
  can1  01A   [8]  11 22 33 44 AA BB CC DD
  can1  01A   [8]  11 22 33 44 AA BB CC DD
  can1  01A   [8]  11 22 33 44 AA BB CC DD
  can1  01A   [8]  11 22 33 44 AA BB CC DD
  can1  01A   [8]  11 22 33 44 AA BB CC DD
  can1  01A   [8]  11 22 33 44 AA BB CC DD
  can1  01A   [8]  11 22 33 44 AA BB CC DD

```

{% endtab %}
{% endtabs %}