Serial Data Transfer Khadas (Android) and Arduino

I have connected an Arduino, to my Khadas which has android running on it. I wish to send and receive data using the GPIO pins, I followed this guide:
But I have not been able to send data from Khadas to Arduino, I know that as the RX light on Arduino does not light up. I tried the Command shell method using termux too and does not work for me too.
I just want to know how to send data over to arduino.

Hi Chetu:
Can you specify more details on these, may be you can just post the commands you ran on VIM2.

Have fun!

As a first troubleshoot I would try to brigde RX and TX (without the Arduino connected).
You should be able to receive what you send.
When that works you know that the software-part is running fine. If you didn’t receive any data back, you not sending data out.