Electronic Scratch Paper

1
Electronic Scratch Paper

• Simon Huang
• Stamford Hwang
• Ted Wang

2
Agenda

• Introduction
• Components
• Improvements
• QA

3
Purpose

• Records information anywhere, anytime
• Reduces the use of paper
• Acts as a whiteboard
• Works as a portable device

4
System Components

• Altera DE2 FPGA Board
• 17.1 Touch Screen
• 17.1 LCD Monitor
• Bilateral Switch (CD4016CN)
• Microprocessor (PIC16F877A)
• A/D Converter (AD573JN)

5
Block Diagram (Hardware)
6
Block Diagram (Software)
7
Agenda

• Introduction
• Components
• Improvements
• QA

8
Touch Screen

• Each Resistor
• 300 O
• Simple Voltage Divider
• Output slightly less than 2.5V
• Scratch of length lt 20µm is ignored

9
Touch Screen to A/D

• Bilateral Switch (CD4016CN) to automate
• On resistance 300 O

10
Wiring
Obtain Y coordinate
Obtain X coordinate
11
A/D Converter (AD573JN)

• A/D Converter to convert analog to 10 bit digital
  signal

12
Wiring

• All 10 bits desired
• Unipolar input
• 0V 5 V
• Input to Convert
• At least gt 500ns wide

1
2
3
13
Tc Conversion Time (30 40 µs) Tcs Convert
Pulse Width (at least 500 ns)
14
Small Spike
15
Parallel to Serial Conversion
16
Protocol of Transmission

• Operates at 10 kHZ

17
State Diagram
18
Why PS/2?

• Complication via USB coding
• Successful testing via PS/2
• i.e. make code of E 24

19
PS/2 vs. RS-232
20
PS/2 vs. RS-232 (cont.)

• Data
• Not Implemented
• Ground
• Vcc (5V)
• Clock
• Not Implemented

21
LCD Controller

• Purpose To control the display of LCD
• Input
• PS/2 serial communication
• Makecode of X and Y coordinate
• Output
• 640 x 480 resolution
• 10 bit RGB VGA signal

22
Block Diagram of LCD controller
23
Decoder

• Purpose Translate PS/2 Protocol to X and Y
• Input
• Makecode of X and Y coordinate
• Output
• X position (0 640)
• Y position (0 480)

24
State Machine

• Purpose CPU to determine functionality
• Input X and Y coordinates
• Output
• Clear
• Draw
• Save
• Load
• Erase

25
Memory Unit

• Purpose grid like storage for 640 x 480 pixel
  info
• Input
• operation determined by SM
• XY coord of user touch
• Current XY coord VGA is drawing
• Output
• RGB signal

26
VGA Driver

• Purpose Calculate correct VGA signals
• Input RGB of pixel
• Output
• VGA Signals
• XY of next pixel draw

27
Agenda

• Introduction
• Components
• Improvements
• QA

28
Improvements

• Include an amplifier to increase the resolution
• Utilize NIOS2 to program through USB A/D
  Converter
• Improve the resolutions shown on the monitor
• Improve circuitry through other means
• Use RAM instead of registers to increase the
  amount of data stored

29
Agenda

• Introduction
• Components
• Improvements
• QA

30
QA