Hi all, I am new here so I often dealing some problems, and it never ends! 
Could you help me please in these issue? I will make a list that I made before step by step:
Note: I am trying to run my micrortps_client in px4 side and micrortps_agent in my companion computer ( this is my Linux 20.04 LTS pc)
- I am using two UART TTL USB converter (CP2102) which are connecting to my Holybro Durandal controller’s TELEM1 and TELEM2 ports,and I only connected CP2102’s Rx,Tx and GND to TELEM’s Tx,Rx,GND respectively. I powered my controller with usb cable which came with it, I connect to my pc usb port.
- I opened new terminal and command:
ls /dev/tty*
then I got the
/dev/ttyACM0 I know it powers my controller
/dev/ttyUSB0 this is for client side
/dev/ttyUSB1 this is for agent side - And also I command lsusb and I saw it Product ID’s of two CP2102 are same. ( I guess it may cause the error but I have doubts because I am not sure.)
- I tried to connect to my client loging to nsh and command firstly:
nsh> mavlink status
instance #0:
mavlink chan: #0
type: GENERIC LINK OR RADIO
flow control: OFF
rates:
tx: 1010.9 B/s
txerr: 0.0 B/s
tx rate mult: 1.000
tx rate max: 1200 B/s
rx: 17.0 B/s
rx loss: 0.0%
Received Messages:
sysid:255, compid: 0, Total: 19 (lost: 0)
FTP enabled: YES, TX enabled: YES
mode: Normal
MAVLink version: 1
transport protocol: serial (/dev/ttyS1 @57600)
instance #1:
mavlink chan: #1
type: GENERIC LINK OR RADIO
flow control: OFF
rates:
tx: 11725.7 B/s
txerr: 0.0 B/s
tx rate mult: 1.000
tx rate max: 46080 B/s
rx: 0.0 B/s
rx loss: nan%
FTP enabled: YES, TX enabled: YES
mode: Onboard
MAVLink version: 1
transport protocol: serial (/dev/ttyS2 @921600)
then
nsh> micrortps_client start -t UART -d /dev/ttyS2 -b 460800
INFO [micrortps_client] UART transport: device: /dev/ttyS2; baudrate: 460800; poll: 1ms; flow_control: No
nsh> micrortps_client status
up and running for 18.579 seconds
nr. of messages received: 0
nr. of messages sent: 5635
total data read: 0 bytes
total data sent: 700132 bytes
rates:
rx: 0.000 kB/s
tx: 37.591 kB/s
avg rx: 0.000 kB/s
avg tx: 37.696 kB/s
tx rate max: Unlimited
I think there is not any problem. (?)
5. I opened new terminal to reach my agent side, then I command to logging in to px4_ros_com_ros2 folder:
micrortps_agent -t UART -d /dev/ttyUSB0
--- MicroRTPS Agent ---
[ micrortps_agent ] Starting link...
[ micrortps_agent ] UART transport: device: /dev/ttyUSB0; baudrate: 460800; poll: 1ms; flow_control: No
[ micrortps_transport ] Error while trying to read serial port configuration: 25
[ micrortps_transport ] Error while trying to write serial port latency: 25
[ micrortps_transport ] Closed UART.
[ micrortps_agent ] EXITING...
then I faced with this issue, I though that It may come from permissions then I command
~ /dev $ chmod 777 ttyUSB1, but it didn’t work.
If you faced with issue before with HOLYBRO DURANDAL or smilar , I will aprecitate with your solutions.
Thanks a lot!