RCP communication not working with TI CC1352 as radio and linux host system as Host over ttyUSB0

[HirenBhuvaMSI]

Hello Community,

I am trying to run RCP firmware on TI CC1352 developement kit hardware using Linux(Ubuntu 22.04) as Host system using https://github.com/openthread/ot-br-posix.
I am able to form Thread Network using /dev/ttyACM0 interface.
However, I need to use /dev/ttyUSB0 interface connected with USB to TTL hardware.

I am getting below error in case of USB0 interface.

Apr 22 18:47:22 hiren-ASUS-EXPERTBOOK-B1503CVA-B1503CVAB systemd[1]: Started OpenThread Border Router Agent.
Apr 22 18:47:22 hiren-ASUS-EXPERTBOOK-B1503CVA-B1503CVAB otbr-agent[1268822]: [NOTE]-AGENT---: Backbone interface: wlo1
Apr 22 18:47:22 hiren-ASUS-EXPERTBOOK-B1503CVA-B1503CVAB otbr-agent[1268822]: [NOTE]-AGENT---: Running 0.3.0-thread-reference-20250612-333-g5bcdd573
Apr 22 18:47:22 hiren-ASUS-EXPERTBOOK-B1503CVA-B1503CVAB otbr-agent[1268822]: [NOTE]-AGENT---: Thread version: 1.4.0
Apr 22 18:47:22 hiren-ASUS-EXPERTBOOK-B1503CVA-B1503CVAB systemd[1]: otbr-agent.service: Main process exited, code=exited, status=5/NOTINSTALLED
Apr 22 18:47:22 hiren-ASUS-EXPERTBOOK-B1503CVA-B1503CVAB otbr-agent[1268822]: [NOTE]-AGENT---: Thread interface: wpan0
Apr 22 18:47:22 hiren-ASUS-EXPERTBOOK-B1503CVA-B1503CVAB systemd[1]: otbr-agent.service: Failed with result 'exit-code'.
Apr 22 18:47:22 hiren-ASUS-EXPERTBOOK-B1503CVA-B1503CVAB otbr-agent[1268822]: [NOTE]-AGENT---: Radio URL: spinel+hdlc:///dev/ttyUSB0?uart-baudrate=921600&uart-flow-control=0
Apr 22 18:47:22 hiren-ASUS-EXPERTBOOK-B1503CVA-B1503CVAB otbr-agent[1268822]: [NOTE]-AGENT---: Radio URL: trel://wlo1
Apr 22 18:47:22 hiren-ASUS-EXPERTBOOK-B1503CVA-B1503CVAB otbr-agent[1268822]: [NOTE]-ILS-----: Infra link selected: wlo1
Apr 22 18:47:22 hiren-ASUS-EXPERTBOOK-B1503CVA-B1503CVAB otbr-agent[1268822]: [INFO]-RCP_HOS-: OpenThread log level changed to 4
Apr 22 18:47:22 hiren-ASUS-EXPERTBOOK-B1503CVA-B1503CVAB otbr-agent[1268822]: 55d.08:09:45.285 [C] Platform------: Init() at hdlc_interface.cpp:153: No such file or directory

I verified my UART communication is working fine using the sample UART Echo project in TI board.

Please help to understand the same.

[HirenBhuvaMSI]

I found that after removing uart-flow-control=0 from my config (/etc/default/otbr-agent) file, I am able to communicate using ttyUSB0 interface as well.
So, it looks like some parsing issue in the otbr-agent.

[jwhui]

Glad to hear that removing uart-flow-control=0 resolved the issue.

The reason this happened is that the uart-flow-control parameter in the OpenThread Radio URL is currently implemented as a presence-based flag.

To ensure flow control is disabled, you should continue to omit the uart-flow-control parameter.