Analog Interface

Everything started with this small board on which I soldered an even smaller chip!

The board is 0,9 by 1,2 cm large and the distance between the pins of the chip is 0,65 mm.

The chip is a digital potentiometer: it receives a 7 bits value, and transforms it into a resistor value from 0 to 5 kΩ.

On the Arduino Side

To test the , I connected to chip outputs to my digital multimeter and played with the 7 bits values.

Here's an example at 3,5 kΩ:

on the LCD, the 7 bits value sent / maximum range * 5 kΩ gives 3,5 kΩ
on the DMM, the measure shows 3,55 kΩ

Pretty close!

On the Robo TX Controller Side

• WARNING AND DISCLAIMER
This sensor is not part of the fischertechnik system.
Bad connection could damage your TX controller.
Take appropriate precautions.
You do it at your own risks.

Now, let's try with the Robo TX controller! The 5 kΩ digital potentiometer could be considered as an RTC.

The main program reads the 5 kΩ analog input i1 and displays it on the TX screen.

Below, an example at 4,7 kΩ:

on the LCD, the 7 bits value sent / maximum range * 5 kΩ gives 4,7 kΩ
on the TX controller, the measure shows 5,0 kΩ

That's not so bad.

Interfacing an Arduino to a Robo TX Controller

Digital Interface