Softwares to Download:

1. Install Arduino Hex Uploader App
2. Download Arduino Hex. Unzip the content of the zip file (serialcoinslot-xxxxx.zip).

After downloading the needed softwares, connect the Arduino to your Android phone via OTG. Make sure you enable the OTG setting on your android.

Open Arduino Hex Uploader App and tap the Arduino device in the list. Tap Ok if prompted to Allow Arduino Hex Upload to access USB2.0-serial.

Then Select the Arduino firmware you downloaded:

Select the arduino board and tap the icon on the bottom-right to start flashing. Wait for the Upload success message.