1

COMP541COMP541

Input Devices: Keyboards, Input Devices: Keyboards, Mice and JoysticksMice and Joysticks

Montek SinghMontek Singh

Apr 16, 2012Apr 16, 2012

Keyboard InterfaceKeyboard Interface

3

PS/2 KeyboardPS/2 Keyboard Uses a synchronous serial protocolUses a synchronous serial protocol

What does that mean?What does that mean? Each symbol is transmitted bit-by-bitEach symbol is transmitted bit-by-bit

8 data bits + 3 control bits8 data bits + 3 control bits

4

Physical InterfacePhysical Interface Two linesTwo lines

Clock (15-20KHz)Clock (15-20KHz) DataData Normally high, asserted Normally high, asserted

lowlow

Read:Read: pp 13-14 of Nexys 3 pp 13-14 of Nexys 3

manualmanual

5

ProtocolProtocol BidirectionalBidirectional

Kybd-to-host and host-to-kybd on same wiresKybd-to-host and host-to-kybd on same wiresCAPS LOCK light for exampleCAPS LOCK light for example

Assert lowAssert low To send, keyboard starts clockingTo send, keyboard starts clocking

sends successive bit on positive edge of clocksends successive bit on positive edge of clockhost reads bits on negative edges of clockhost reads bits on negative edges of clock

You shouldnYou shouldn’’t need to send to kybdt need to send to kybd

ProtocolProtocol 11 bits11 bits

a start bit: always 0a start bit: always 0 8 bits of data8 bits of data

lsb firstlsb first one parity bit (odd)one parity bit (odd) a stop bit: always 1a stop bit: always 1

Clocked by keyboardClocked by keyboard Value should be latched by FPGA on neg edge of Value should be latched by FPGA on neg edge of

keyboard clockkeyboard clock

6Illustration from http://www.beyondlogic.org/keyboard/keybrd.htm

7

What is SentWhat is Sent ASCII is not sent!ASCII is not sent! Scan codes for keysScan codes for keys

Most keys have an 8-bit (single byte) scancodeMost keys have an 8-bit (single byte) scancode Some have two bytesSome have two bytes A few have even more!A few have even more! Most (not all, be careful!) keyboards use these Most (not all, be careful!) keyboards use these

scancodes:scancodes:

Illustration from Nexys 3 manual

8

Scan CodesScan Codes Normally translated by softwareNormally translated by software

You remap your keys, for exampleYou remap your keys, for example

Software takes care ofSoftware takes care of Shift, caps lock, controlShift, caps lock, control

9

Some Scan Codes LongSome Scan Codes Long Two code sequence commonTwo code sequence common

Have a look at Break key!Have a look at Break key!

10

Even More ComplicatedEven More Complicated Scan code generated when you pressScan code generated when you press And when you releaseAnd when you release

Two bytes: F0 followed by key scan codeTwo bytes: F0 followed by key scan code Example:Example:

Space pressed, 29 sentSpace pressed, 29 sentSpace released, F0 29 sentSpace released, F0 29 sent

If you hold key, scan code repeatedIf you hold key, scan code repeated

11

ResourcesResources InformationInformationhttp://www.beyondlogic.org/keyboard/keybrd.htm

Scan codesScan codeshttp://www.barcodeman.com/altek/mule/scandoc.php

My Verilog for keyboard is on the class websiteMy Verilog for keyboard is on the class website

12

My VerilogMy Verilog Have Verilog for keyboardHave Verilog for keyboard Have tested it with the FPGA kit; seems to Have tested it with the FPGA kit; seems to

work finework fine To use:To use:

You should memory-map the character code registerYou should memory-map the character code registergive the keyboard a memory address so the CPU can read give the keyboard a memory address so the CPU can read

it using it using lwlw instructions instructions Handle presses and releases appropriately in softwareHandle presses and releases appropriately in software

maybe add another register to indicate that a new maybe add another register to indicate that a new character has arrived..??character has arrived..??

MiceMice

13

MouseMouse Very similar interface (clk & data)Very similar interface (clk & data)

But: 3 words sent w/ mouse movement or button But: 3 words sent w/ mouse movement or button presspress

ReadRead pp 14-15 of Nexys 3 manualpp 14-15 of Nexys 3 manual

14

MovementMovement Movement is relativeMovement is relative

XS, YS are sign (+ is up/right)XS, YS are sign (+ is up/right) XV, YV are overflow (too fast)XV, YV are overflow (too fast) L, R are buttonsL, R are buttons

15

Scroll Wheel, etc.Scroll Wheel, etc. Extensions to original 2 button PS/2 mouseExtensions to original 2 button PS/2 mouse

See See http://www.computer-engineering.org/ps2mouse/

16

JoystickJoystick

(Courtesy Anselmo Lastra)(Courtesy Anselmo Lastra)

Atari 2600 Joystick (we only have Atari 2600 Joystick (we only have 2-3)2-3)

18

http://www.atariarchives.org

We Have Sega Joypads (we have We Have Sega Joypads (we have 5-6)5-6) Enhanced version with Enhanced version with

more buttonsmore buttons Has muxHas mux Select pin chooses first or Select pin chooses first or

second set of buttons, second set of buttons, L/RL/R

19http://pinouts.ru/data/genesiscontroller_pinout.shtml

Six Button UseSix Button Use SeeSee

http://www.cs.cmu.edu/~chuck/infopg/segasix.txthttp://www.cs.cmu.edu/~chuck/infopg/segasix.txt

Use select to use buttons B & CUse select to use buttons B & C To use X, Y, Z, need to pulse selectTo use X, Y, Z, need to pulse select

20

NEXYS Mappings (PMOD JA)NEXYS Mappings (PMOD JA) We have to connect them using wires…We have to connect them using wires…

21

Signal FPGA Pin DB-9 10-Pin

Up M15 1 4

Down L17 2 3

Left L16 3 8

Right K12 4 2

Btn A/B M14 6 9

Start/C L15 9 1

Select M16 7 10

Ground - 8 5

Power - 5 6PMOD JA is 10-pin connector nearest VGA connector

SuggestionSuggestion Create FF for SelectCreate FF for Select

Memory map so you can set from CPUMemory map so you can set from CPU

Memory map the input signalsMemory map the input signals I would not latch themI would not latch them

Please power off when plugging or unplugging Please power off when plugging or unplugging Sega joypads!Sega joypads! Careful when plugging in PCBCareful when plugging in PCB

22

23

LinksLinks http://pinouts.ru/data/JoystickAtari2600_pinout.shtmlhttp://pinouts.ru/data/JoystickAtari2600_pinout.shtml http://pinouts.ru/data/genesiscontroller_pinout.shtmlhttp://pinouts.ru/data/genesiscontroller_pinout.shtml http://www.epanorama.net/documents/joystick/ataristick.htmlhttp://www.epanorama.net/documents/joystick/ataristick.html http://www.epanorama.net/documents/joystick/tvgames.htmlhttp://www.epanorama.net/documents/joystick/tvgames.html

http://www.cs.cmu.edu/~chuck/infopg/segasix.txthttp://www.cs.cmu.edu/~chuck/infopg/segasix.txt