Problems with config ATA to send and receive Fax

I am trying to build an ATA device based on OpenWrt. I have made the call work but got no luck with fax.
Here is my topology:
Traditional Fax <==> OpenWrt ATA <==> RasPBX <==> OpenWrt ATA <==> Traditional Fax
The RasPBX is using asterisk 13 and the ATAs are using asterisk 11.
I have configured RasPBX using Chan_SIP and allow T38 in Chan_SIP settings. On ATAs I have check that module and are loaded. I have read Asterisk the Definite Guide and set t38pt_udptl = yes in sip.conf. But the fax still not work.
I think the main problem is how I configure my ATA device, because I have other commercial ATA (not OpenWRT based) that can fax well using the same scenario.
Can somebody help me? What things I have miss in my setup?

So, you are saying that your setup works when you use a commercial ata, but not when using the OpenWrt “ata”?

Then I would ask this question in the openwrt forum…

When I google “openwrt as ata” the first result I get is “OpenWrt as ATA voip adapter (Page 1) — General Discussion”

Also for the people on this forum to help you more information is needed. By just telling how your setup is done, it is impossible to provide any solution.

I would start with checking the asterisk log file to see if the there is a callsetup from the one fax to the other…

If that call is established, then you need to analyse the log files on the openwrt ata’s.

Good luck.