An Android phone uses Bluetooth to remotely control a regular VGA monitor that will display used to display a ping-pong scoreboard.
This VGA scoreboard project illustrates the interaction of the Bluetooth module with the Atmel ATtiny45 which can run at 20MHz with an external oscillator but with a very limited number of I/O pins. The 4 available pins will be used for the VGA HSYNC, VSYNC and RGB generation. The Bluetooth will wait for a connection from a device and will act as Serial Port Profile (SPP) re-passing everything received from the device to the UART interface. It is a one way communication since the ATtiny will read the data but won’t speak back to the module.
The main function of the ATtiny45 is to display the current scores in a VGA monitor while reading from a Bluetooth module UART interface waiting for commands that will tell it what to display. An application specially designed for this project is run as the Android device sends the commands via Bluetooth. To set the characters that must be displayed and to indicate who is currently serving by displaying a little square on the corners of the screen, a set of commands is defined.
Attached to PIN24 of the Bluetooth module is a blue LED that will blink while the module is waiting for a connection and will keep ON in an established connection. For convenience, the scores can be controlled with the Volume Up/Down keys.