Arduino with blynk app using USB Serial

Use usb-serial-for-android app to send data from your phone to arduino or any serial device

Control USB Serial ANDROID en ARDUINO

How to Capture and Save Arduino USB Serial Data

Servo USB APP INVENTOR 2 Arduino at 115200 bauds

SHORT TEST - Android - Arduino Communication via USB Serial Connection

Setting up OTG communication with MIT app inventor

Check idVendor and idProduct of USB device, Arduino Uno