B410P loop back test fails - Unexpected Result, 255 != 0, 1

Hi, i have contacted Digium support about a B410P card that could not make or receive calls. They were very helpful and sent me through instructions for loop back test. After the loop back test failed, they RMA’d the card super-fast 8) the only problem is that i now have the replacement card (different serial number) and it is doing the exact same thing, and is failing the loopback test.

I would like to post the procedure here just to check i am not doing something stupid:

I have tried this on different machines on different hardware, both 32-bit and 64-bit CentOS 5.5, and Asterisk 1.8 and Dahdi 2.4, installed via yum, and I get the same loopback test error.

First I configured port 1 of the quad port card for NT by putting the jumper to the left and enabling the 100ohm impedance switch.

The other channels were left in TE mode.

I then plugged in a loop back cable (normal straight through Cat5e cable) to ports 1 and 2 (furthest ports away from the PCI backplane).

I then configured dahdi to use the channels with dahdi_genconf, and then edited the /etc/dahdi/system.conf to make port 1 the clock master, and the other ports slaves:

[root@pbx dahdi]# cat system.conf

Span 1: B4/0/1 “B4XXP (PCI) Card 0 Span 1” (MASTER) AMI/CCS RED


termtype: nt


Span 2: B4/0/2 “B4XXP (PCI) Card 0 Span 2” AMI/CCS


termtype: te


Span 3: B4/0/3 “B4XXP (PCI) Card 0 Span 3” AMI/CCS


termtype: te


Span 4: B4/0/4 “B4XXP (PCI) Card 0 Span 4” AMI/CCS


termtype: te


Global data

loadzone = us
defaultzone = us

I issued /etc/init.d/dahdi restart, and the modules and config load up fine. dahdi_tool shows ports 1 and 2 are OK, with red on ports 3 and 4.

I then run the test pattern generator and listener on separate SSH sessions:

[root@pbx dahdi]# patgen /dev/dahdi/1
[root@pbx ~]# pattest /dev/dahdi/2

I get hundreds of errors instantly:

Unexpected Result, 255 != 0, 1 bytes since last error

The questions I have are:

Did I do the test correctly?
If the ports are shown in sync via dahdi_tool and solid green lights on the back of the card, then why do I get errors?
Any ideas what i should do next?!

I greatly appreciate any advice you may have, i am not sure what i should try next, i don’t believe the second card is also faulty i must be doing something wrong!

Thanks in advance,


It’s been a while for me, so please forgive misremeberances… :wink:

[root@pbx dahdi]# patgen /dev/dahdi/1
[root@pbx ~]# pattest /dev/dahdi/2

In this case you’re running it against two channels that are on the same span (port), no? You should be gen’ing against channel 1 and testing against channel 4.