1 / 24

COMP541 Input Devices: Keyboards, Mice and Joysticks

COMP541 Input Devices: Keyboards, Mice and Joysticks. Montek Singh Nov 3, 2014. Keyboard Interface. USB keyboard plugs into the USB port on Nexys 3 / Nexys 4 boards. USB to PS /2 emulation. Host controller on Nexys boards t alks to USB keyboard on one side

danielle-pena
Download Presentation

COMP541 Input Devices: Keyboards, Mice and Joysticks

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. COMP541Input Devices: Keyboards, Mice and Joysticks Montek Singh Nov 3, 2014

  2. Keyboard Interface USB keyboard plugs into the USB port on Nexys 3 / Nexys 4 boards

  3. USB to PS/2 emulation • Host controller on Nexys boards • talks to USB keyboard on one side • speaks PS/2 protocol to the FPGA on the other side • PS/2 used to be the dominant keyboard protocol • PS/2 = a synchronous serial protocol • What does that mean? • Each symbol is transmitted bit-by-bit • 8 data bits + 3 control bits • synchronized to the keyboard’s clock (slow)

  4. Physical Interface • Two lines • Clock (15-20KHz) • Data • Normally high, asserted low • Read: • pp. 13-14 of Nexys 3 manual • pg. 10 of Nexys 4 manual

  5. Protocol • Bidirectional • Kybd-to-host and host-to-kybd on same wires • CAPS LOCK light for example • Assert low • To send, keyboard starts clocking • sends successive bit on positive edge of clock • host reads bits on negative edges of clock • For your lab: • You shouldn’t need to send anything to keyboard

  6. Protocol • 11 bits • a start bit: always 0 • 8 bits of data • lsb first • one parity bit (odd) • a stop bit: always 1 • Clocked by keyboard • Value should be latched by FPGA on neg edge of keyboard clock Illustration from http://www.beyondlogic.org/keyboard/keybrd.htm

  7. What is Sent • ASCII is not sent! • Scan codes for keys • Most keys have an 8-bit (single byte) scancode • Some have two bytes • A few have even more! • Most (not all, be careful!) keyboards use these scancodes: Illustration from Nexys 3 manual

  8. Scan Codes • Normally translated by software • You remap your keys, for example • Software takes care of • Shift, caps lock, control

  9. Some Scan Codes Long • Two code sequence common • Some special keys use even more… • …have a look at Break key!

  10. Even More Complicated • Scan code generated when you press • And when you release • Two bytes: F0 followed by key scan code • Example: • Space pressed, 29 sent • Space released, F0 29 sent

  11. Resources • Information http://www.beyondlogic.org/keyboard/keybrd.htm • Scan codes http://www.barcodeman.com/altek/mule/scandoc.php • Available on the class website: • my Verilog for keyboard

  12. My Verilog • Have Verilog for keyboard • a test/demo which displays data from keyboard onto 7-segment display • have tested it with the FPGA kit; seems to work fine • To use: • You will memory-map the character code register • give the keyboard a memory address so the CPU can read it using lw instructions • Handle presses and releases appropriately in software • Either: Check for a key release before reading a new key press • OR: Delaying next key read (by, say, 1/4th sec) • gives you automatic “key repeat” feature!

  13. Mice

  14. Mouse • Very similar interface (clk & data) • But: 3 words sent w/ mouse movement or button press • Read • pp. 14-15 of Nexys 3 manual / pp. 12-13 of Nexys 4 manual • Verilog • I can guide you to modify keyboard.v to read 3 bytes

  15. Movement • Movement is relative • XS, YS are sign (+ is up/right) • XY, YY are overflow (too fast) • L, R are buttons

  16. Scroll Wheel, etc. • Extensions to original 2 button PS/2 mouse • See http://www.computer-engineering.org/ps2mouse/

  17. Joystick

  18. Joystick module • 2 axes: x and y • 10-bit position values • On-board microprocessor • handles debouncing • communicates with host • Info on class website • reference manual • Verilog code • demo: feeds joystick output to the 7-seg display • you will modify to feed the output into your memory-mapped I/O unit instead

  19. Accelerometer Nexys 4 boards have built-in accelerometer For Nexys 3: read on…

  20. Accelerometer module • 3-axis accelerometer • x, y, z components of gravity • helps determine • orientation and acceleration • On-board microprocessor • communicates with host • Info on class website • reference manual • Verilog code • demo: feeds accelerometer output to the 7-seg display • you will modify to feed the output into your memory-mapped I/O unit instead

  21. Keypad

  22. Keypad module • 4x4 keypad • 0-9, A-F • one hex character input • Simple interface • 4-bit row, 4-bit column • a ‘0’ means pressed • Info on class website • reference manual • Verilog code • demo: feeds keypad output to the 7-seg display • you will modify to feed the output into your memory-mapped I/O unit instead

  23. Stereo Audio Amplifier Nexys 4 has mono amplified built-in Nexys 3/Nexys 4: you can attach a stereo module(read on…)

  24. Amplifier module • Stereo output • headphone jack compatible • Very very low-level…! • expects analog waveform oninput! • your design on FPGA will haveto generate an analog valueby rapidly toggling between 0 and 1 • e.g., 60% of the time ‘1’ value will approximate an analog value of 0.60V (if range is 0-1V) • Verilog code • I will post mine on the website

More Related