iotsaDisplayServer - web server to drive an LCD display

iotsaDisplayServer is a web server that drives an LCD display, such as an i2c 4x20 character module. Support for a buzzer (to attract user attention) and buttons (programmable to trigger actions by accessing programmable URLs) is included.

Home page is https://github.com/cwi-dis/iotsaDisplayServer. This software is licensed under the MIT license by the CWI DIS group, http://www.dis.cwi.nl.

Software requirements

• Arduino IDE, v1.6 or later.
• The iotsa framework, download from https://github.com/cwi-dis/iotsa.
• The new LiquidCrystal library, download from <https://github.com/fmalpartida/New-LiquidCrystal.

Hardware requirements

• an esp8266 board, such as an ESP-12, ESP-201 or iotsa board.
• An i2c LCD module.
• Optionally some pushbuttons and a buzzer.

Hardware construction

Instructions for constructing the hardware using an ESP-201 board are provided in the extras subfolder:

• DisplayServer-schematic.pdf has the schematics.
• DisplayServer-breadboard.pdf shows how to put the bits together on a breadboard. The Fritzing project is also available as DisplayServer-bb.fzz.
• DisplayServer-stripboard.pdf shows how to put the bits together on a stripboard. The Fritzing project is also available as DisplayServer-bb.fzz.

Building the software

You may need to modify the defines PIN_ALARM, WITH_LCD and WITH_BUTTONS near the top, to reflect which optional hardware support you want.

A bit further down you specify the LCD parameters with PIN_SDA, PIN_SCL, LCD_WIDTH and LCD_HEIGHT. Depending on the specific LCD you use you may need to make changes in the following few lines.

About half way down the file you specify the GPIO pins to which buttons have been connected, in the initializer of the buttons variable.

Compile, and flash either using an FTDI or (if your esp board supports it) over-the-air.

It is also possible to build variants of this service by specifying iotsa build flags:

• -DIOTSA_WITHOUT_HTTP -DIOTSA_WITH_HTTPS builds a version that uses https (for securing your display)
• -DIOTSA_WITHOUT_HTTP -DIOTSA_WITHOUT_REST -DIOTSA_WITH_COAP builds a version with no web interface and no REST interface. In stead, the API is exposed over UDP using the COAP protocol. This could be used for an low-power version if you have a suitable low power display.

Operation

The first time the board boots it creates a Wifi network with a name similar to config-iotsa1234. Connect a device to that network and visit http://192.168.4.1. Configure your device name (using the name lcd is suggested), WiFi name and password, and after reboot the iotsa board should connect to your network and be visible as http://lcd.local.

Visit http://lcd.local/display to show a message on the display, and/or produce a sound with the beeper.

Visit http://lcd.local/buttons to configure the URLs for the buttons. Whenever a button is pressed an http GET request is sent to the corresponding URL.

There is a command-line tool (for Linux or MacOSX) in extras/lcdecho that allows you to show messages and control the other parameters programmatically, use

lcdecho --help

for help.