MK15 UART telemetry

Hello
Try to use UART interface for transmition telemetry data.
I configured SIYI TX Datalink Settings - UART, Baud Rate by default.
Create comm links into QGS
I don’t see any data, what I wrong do?
@SIYI

Please show us a complete video of your operation along with the complete connection of the datalink from remote controller to flight controller and air unit

At first, configure MK15 by mobile app SIYI TX
Main menu - Datalink - Connection - UART
Main menu - Datalink - Baud Rate (can’t change and left by default)

At second,
QGroundControl - Application Settings - Comm Links
Add new comm link
Name: uart
Type: Serial
Serial Port: bus/usb/001/003 (by default, after first point, this field fill auto)
Baud Rate: 57600
Advanced Settings: 8N1

And after that start to find UART connector in MK15 and don’t find (but reference said that we can communicate using UART)
I need to solve my issue, using wired interface (for example, UART) send/receive telemetry data