Project Idea: SPACE INVADERS (In collaboration with Ryan McAliney)

• Will try to implement game Space Invaders for the FPGA board using VHDL. Inputs are being taken from the keyboard and the output is displayed over the VGA port.

• Each line of the video begins with an active video region, in which RGB values are output for each pixel in the line. Then a blanking region follows in which a horizontal sync pulse is transmitted in the middle of the blanking interval.
• The Nexys A7 board uses 14 FPGA signals to create a VGA port with 4 bits-per-color and the two standard sync signals. The color signals use resistor-divider circuits that work in conjunction with the 75-ohm termination resistance of the VGA display to create 16 signal levels each on the red, green, and blue VGA signals.
• This circuit shown produces video color signals that proceed in equal increments between 0V and 0.7V. Using this circuit, 4096 different colors can be displayed, one for each unique 12-bit pattern.

• The clock and data signals are only driven when data transfers occur; otherwise, they are held in the idle state at high-impedance. This requires that when the PS/2 signals are used in a design, internal pullups must be enabled in the FPGA on the data and clock pins.
• The clock signal is normally driven by the device, but may be held low by the host in special cases. The timings define signal requirements for mouse-to-host communications and bi-directional keyboard communications. A PS/2 interface circuit can be implemented in the FPGA to create a keyboard or mouse interface. The same interface we will implement in order to play the game.

• The Auxiliary Function microcontroller hides the USB HID protocol from the FPGA and emulates an old-style PS/2 bus. The microcontroller behaves just like a PS/2 keyboard or mouse would. This means new designs can re-use existing PS/2 IP cores. Mice and keyboards that use the PS/2 protocol use a two-wire serial bus (clock and data) to communicate with a host. On the Nexys A7, the microcontroller emulates a PS/2 device while the FPGA plays the role of the host. Both the mouse and the keyboard use 11-bit words that include a start bit, data byte, odd parity, and stop bit, but the data packets are organized differently, and the keyboard interface allows bidirectional data transfers. Using a wireless USB keyboard we will be able to control our rocket ship to destroy enemy aliens.