16-04-2012, 12:27 PM
Customizable Virtual Keyboard
[attachment=20132]
Introduction
It is becoming increasingly difficult for users to interact with the slew of portable gadgets they carry, especially in the area of text entry. Although miniature displays and keyboards make some portable devices, such as cell phones and PDAs, amazingly small, users’ hands do not shrink accordingly.
High Level Design
The Virtual Keyboard has three main components: the laser, camera, and printed keyboard. The laser beam is simply a conventional off-the-shelf red laser with a line-generating diffractive optical element attached to it. This assembly generates an invisible plane of red light hovering a few millimeters above the typing surface. When a finger passes through this plane, it shines bright red in that region.
Software Implementation
The software component was split into 5 main components:
• Implementing the I2C protocol to read and write registers from camera
• Reading values from camera to obtain 6 frames every second
• Processing the images to obtain a pressed key
• Converting the pressed key into a scan code which is then transmitted using the PS/2 protocol
• Sending serial data from a java application to update the array of scan codes in the Mega32
Image Processing
The getRedIndex function captures rows of data from the camera and processes each of them. We first wait until a neg edge on the VSYNC, which indicates the arrival of new frame data on the UV and Y lines. We then wait for one HREF to go by since the first row of data is invalid. At this point, we can clock in 176 pixels of data for a given vertical line in the Bayer format.
Keyboard Output (PS/2)
The code was structured using two timer compare interrupts where timer1 compare was used to start transmissions of each data byte and timer2 compare was used to reset the waiting. Since the protocol allows a range of frequencies that a computer would understand, we decided to use a clock time of 250 and wait time of 700. When the timer1 interrupt is fired, it transmits the bits in the following order when the clock is set to high: start bit(0), data bits, parity bit(xor of all bits), and a stop bit(1).
Conclusion
Although the final project was very satisfying, our results did not completely meet our expectations. The keyboard worked as we predicted but typing speed was minimal (about 60 characters per minute) due to limited processing capabilities of the Mega32 microcontroller.
[attachment=20132]
Introduction
It is becoming increasingly difficult for users to interact with the slew of portable gadgets they carry, especially in the area of text entry. Although miniature displays and keyboards make some portable devices, such as cell phones and PDAs, amazingly small, users’ hands do not shrink accordingly.
High Level Design
The Virtual Keyboard has three main components: the laser, camera, and printed keyboard. The laser beam is simply a conventional off-the-shelf red laser with a line-generating diffractive optical element attached to it. This assembly generates an invisible plane of red light hovering a few millimeters above the typing surface. When a finger passes through this plane, it shines bright red in that region.
Software Implementation
The software component was split into 5 main components:
• Implementing the I2C protocol to read and write registers from camera
• Reading values from camera to obtain 6 frames every second
• Processing the images to obtain a pressed key
• Converting the pressed key into a scan code which is then transmitted using the PS/2 protocol
• Sending serial data from a java application to update the array of scan codes in the Mega32
Image Processing
The getRedIndex function captures rows of data from the camera and processes each of them. We first wait until a neg edge on the VSYNC, which indicates the arrival of new frame data on the UV and Y lines. We then wait for one HREF to go by since the first row of data is invalid. At this point, we can clock in 176 pixels of data for a given vertical line in the Bayer format.
Keyboard Output (PS/2)
The code was structured using two timer compare interrupts where timer1 compare was used to start transmissions of each data byte and timer2 compare was used to reset the waiting. Since the protocol allows a range of frequencies that a computer would understand, we decided to use a clock time of 250 and wait time of 700. When the timer1 interrupt is fired, it transmits the bits in the following order when the clock is set to high: start bit(0), data bits, parity bit(xor of all bits), and a stop bit(1).
Conclusion
Although the final project was very satisfying, our results did not completely meet our expectations. The keyboard worked as we predicted but typing speed was minimal (about 60 characters per minute) due to limited processing capabilities of the Mega32 microcontroller.