Circuit Lake

Electronic Project and Circuit Collection

Head-Controlled Keyboard And Mouse For Disabled, AVR ATMega32

10/07/2012 Category: AVR, Control, Interfacing, Wireless

Easy Input is a head-controlled keyboard and mouse input device for paralyzed users. The system is built based on AVR ATMega32. It uses user’s head movement to control mouse movement on the monitor and user’s eye blinking to activate mouse click. Two main sensor used for this project are Freescale MMA6560Q accelerometers to detect head tilt and photodiode to detect user’s eye blinking.

AVR Head-Controlled Keyboard And Mouse

Sensor outputs are sent to microcontroller ATmega32 via A/D converter. After processed by MCU, the data is transmitted remotely using wireless protocol. On the other side, a wireless receiver collects all the correct information through id filtering and then sends signals to a ground microcontroller through USART for interpretation process. After interpreted, mouse or keyboard instructions are sent to the computer via PS/2-to-USB cable.

The system has two operation modes: mouse mode and keyboard mode. When it is in mouse mode, the X and Y movements are directly mapped to the movement of mouse. The more your head tilts, the faster the mouse moves. When the user blinks, the mouse clicks. To distinguish between the unintentional blink and intentional blink, the program has to receive 10 consecutive blink packets from the transmitter to actually send a mouse click signal to the computer.

mouse mode diagram

In keyboard mode, user select the character that he want to enter by tilting head right or left. The English characters are arranged by their frequency to speed up the selection. The scrolling of characters is done by sending a backspace signal before sending the characters. The characters are scrolling at a rate of 2.5 cps. When you reach the character user want, user can blink to start a new character selection. When user tilts head up, user can change between lower case, upper case, number and punctuation. When you tilt the head down, a backspace signal is sent to the computer. To switch between the mouse and keyboard mode, you need to close your eye for about 4 seconds.

keyboard mode diagram