This project is installed in the scout clubhouse in Polná. It involves multimedia control in the common room using three buttons. The objective was to eliminate the need for a remote control for the audio amplifier, data projector, and projection screen. Additionally, simplifying the control of the bluetooth receiver was necessary.

The audio amplifier supports digital inputs through SPIDF (Toslink), and it was important to devise a variant that would maintain the quality. Furthermore, digital transmission allows for the transmission of 5.1 audio signals. The first device that requires control is the bluetooth receiver. The chosen receiver lacks digital control capability, so the MCU control buttons had to be connected instead. To ensure proper operation, feedback was needed in the form of a signal from an LED light.

Next, control over the audio amplifier was necessary. The amplifier is controlled using an IR remote control, specifically following the NEC IR communication protocol. To simplify this, a pre-made module was utilized to convert IR communication into a UART serial line (known as the YS-IRTM T5.01 module). Through this module, the audio amplifier can be turned on and off, and the user can switch between two digital inputs and one analog input, as well as enable or disable Mute.

Controlling the data projector and projection screen was also essential. Controlling the screen is straightforward, as it has a Trigger input that retracts the screen when +12V is applied and extends it when 0V is applied. The data projector offers two control options. The first is an IR remote control, which is not suitable for the project as it does not provide feedback to the MCU. The second and preferred option is to utilize RS232 data projector communication, which allows for two-way communication. This enables monitoring of the projector’s status, such as power on, on, cooling down, and power off, as well as detecting any errors, such as a faulty lamp, overheating, or a clogged dust filter.

The control system consists of three buttons, one potentiometer, and a switch. The first button controls the bluetooth, the second button turns on the mixing desk and switches all devices to analog mode simultaneously, and the third button controls the data projector. The potentiometer is intended for adjusting the brightness of the data projector, but it is not used in this particular setup, as the current data projector does not support this function. All multimedia devices are powered on and off using the switch. The power supply to all appliances is controlled through relays to prevent unnecessary electricity usage. The device also features a small OLED display that shows current information.

In managing all these devices, consideration was given to all possible combinations of conditions that may arise and attempts were made to handle them in the best possible way. For example, when switching inputs on the audio amplifier, the sound is turned off to avoid noise from the speakers. Additionally, when the switch is turned off, the data projector must cool down and the projection screen must retract before disconnecting from the power supply.