Touchscreen control

Contents:

• Overview
• System Description
• Case study

Overview

The Touchscreen control allows to manipulate many serial enabled peripherals such as AV equipment, lights, power devices, etc.

Touchscreen user interface

The system consists of:

• Touchscreen - the main user interface
• Embedded computer - the brains behind the touchscreen
• Communication modules - command delivery system from user to peripherals
• Adapters, special controls - additional features that expand the control abilities of the system

The system was designed with simplicity and cost-effectiveness in mind. It is easy to configure, the components are affordable, modular design allows for quick and inexpensive expansion.
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System description

Touchscreen

Touchscreen represents a user interface that sends customer input to the embedded computer for further processing. The screen size can be as small as 2'' x 3'' or as big as 24'' monitor.

Embedded system

Raspberry Pi computer connected to the Touchscreen is an affordable yet extremely versatile feature of the system. Powered by lean and responsive Slackware Linux the computer translates user input (normally a button press) into the corresponding command dedicated to a particular device. Custom built protocol provides robust and quick way of delivering the commands to the Communications modules.

Raspberry Pi 3 board

Communication modules

The communications module consists of a master device and a number of slave devices. Master receives the command from the Embedded system and then passes it to one of its slaves. The command transfer works on FIFO low latency principle. The slaves in turn send the command to the peripherals. Main feature of the communication modules is the ability to daisy chain. This expands the number of supported devices from 4 (with single master/slave combo) to 64 (one tier 1 master, 4 tier 2 masters and 16 slaves at tier 3 each connected to 4 peripheral devices). Theoretically there can be any number of peripheral devices with slight modification of the protocol, but at the moment this does not seem to be neither practical, nor necessary.

Prototype

Beta version connected

Master module

Slave module

Special control modules and adapters

By using RJ45 connectors and Cat5 network cables as the main medium of signal delivery the system costs much less to install, than a traditional comms system with RS232 compatible cables. This requires DB9 to RJ45 adapters, which feature Male and Female DB9 ends, as well as the ability to change TX and RX lines in case of end device's reversed communications lines.
Some devices either are too expensive (e.g. power control) or simply do not exist with the serial control enabled. This brings in custom built devices that can overcome this problem. At the moment there are Power control devices and Volume control devices available for production. There are many more in the design stage.

Power control project

Link to the project's hardware description.

Link to the project's code

Power control device

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Case study: AV setup at Massey University

Problem statement

My job was to support AV facilities in various lecture rooms for School of Engineering and Advanced Technology (SEAT). These would include projector output, input from computer/laptop/document camera, microphone setup and sound playback. Often a remote control would get missing, or cables were connected in wrong place, or missing altogether. I would get a call from the room daily, sometimes several calls per day. To mitigate this I designed a centralized control system based on Touchscreen and Raspberry Pi.

Proposed Solution

The solution was to hide potential sources of confusion and route all control through the Touchscreen system. Projectors, audio and VGA switch now were controlled with a simple push of a button on the screen. All cables and remote controls were hidden to prevent tempering with the setup.

Results

The system in the project room is working now over a year. Since its installation the number of fault calls from that particular room has been reduced almost by 80%. The system is very stable, there were no malfunctions or unintended actions by the system. Top