Simplified circuit diagram of PiMu.

Lets start in the middle. The Raspberry Pi 2 board is the heart of PiMu. Per USB there are connected:

• External audio adapter for the speakers and the microphone
• WLAN adapter
• RFID reader
• Fadecandy board

On the left the slider is located. Its connected to the AD/DA converter - the Raspberry Pi 2 has only digital pins. This converter needs a power suppliy and ground, as like the slider. The R-line of the slider is connected to an analog input of the converter. This sends its signals to SCL and SDA Ports of the Raspberry. With the SDA port connected to ground, the Pi can be started. So we have here two inputs on one pin. Due to non readable data when the On/Off button ist pressed, we managed to handle this with our software and compensate the double pin aquirence.

Each button needs to be connected to an GPIO input pin and ground. when the button is pressed, current flows and the Pi interpret this as 1.

The LEDs all need a connection to 5V and ground. The input of the LEDs are bytes with the adress of the LED in the row and the information of which color to show. The Fadecandy board has 7 channels. By them we control the LEDs.

We use a Rav- Powerbank Link. It is an intelligent powerbank adjusting its output to the needs. But the power we need is the maximum of using the Pi reliable. The amplifier and the Pi ist plugged in here. Due to high amperes we recommend to distribute the 5V and ground pins to every part connected.

Microphone and speakers are connected with the external audio adapter. The internal audio of the Pi is not the best, so we decided to this solution.