There are several OTG adapters available or you can hack one. But it will stretch out your tablet in a dangerous way. We designed an as compact as possible adapter that fit close to the tablet. A Molex connector and cable makes it easy to be connected to your application board. The USB to serial chip is a CH340G. Driver is easy to find if not already installed.

A typical application is to replace the Arduino Terminal by the tablet, so you can carry it on your robot or portable application. Many terminal emulators exist. We preferred the "Serial USB Terminal" on android.

Note that the connector include the +5V of the tablet. This is convenient to play with a close-by Arduino bord and test the emulators, but it discharges the tablet battery (30 to 50mA) and is not recommended for more current.

Another application is to replace the BT or WIFI connection, while developing your application, by a direct UART connection with 3 wires. Simple and efficient, pairing problems will not distract you from your algoritms.