µBITS

Chris PagePeter Gimeno

Christina WilliamsGreg Weatherford

Christopher Howard

µBITS - Pictures for the Blind

Designed to provide a tactile display allowing the blind to interact with computers, text, and possibly three dimensional images.

Can allow for communication between physically disabled people across the world.

µBITS Overview – Presentation Outline

Product Overview Initial Requirements Block Diagram Digital Design Process Analog Design Process Project Flowchart Problems and Cost Questions, Comments?

µBITS Product Overview –

A Tactile Display Board Designed for use by the blind. Capable outputting multiple

character sets Flexible I/O interface Integrated Keyboard Support

(USB or PS/2) Software designed to support up

to a 320x240x8 pin display. Compact

Initial Requirements – Environmental Standards

Operation at standard room temperatures.

Safe for end user operation.Compliant with FCC standards.Safe for pacemaker users.

Initial Requirements - Performance Standards

CPU Capable of image/video decoding.

2Mb of frame backing/character lookup memory.

4Mb of CPU memory.

Initial Requirements – Interface Standards

P/S 2 keyboard input Pin Grid Output 2 General purpose I/O inputs

Capable of supporting USB, IDE, Digital Cameras, serial, and many other popular input methods.

Block Diagram

Power supplyDC –DC

converters

ProcessorCY7C67200

50 MHzGCC programmable

Memory4Mb SRAM

Memory2 Mb SRAM

Frame Buffer andCharacter Lookup

Table

Pin Grid

FPGADisplay DriverI/O Controller

Future Expansion

Future I/O Expansion

AnalogDisplay Driver

P/S 2 Input

Digital Design Process

Determine Specification Details Block Diagrams Part selection Schematic Capture Schematic Review Layout Board Manufacturing (if possible) Interface / Test / Debug Implementing additional features.

Analog Design Process

Layout of Pin Board (LPB) Ideas for Pin Elevation (PE) Ideas for Implementation

MUX Decoder Current Amplifier PWM

First Prototype Board First Prototype Analysis Checklist Next Steps (Prototype and Beyond)

AnalogDisplay Driver

Pin Grid

Power supplyoverall

Analog Design: Layout of Pin Board (LPB)

Initially, we will work towards a 2D board similar to the board seen in the picture on the left.

Hopefully, for 3D contour, we will need to be able to elevate the pins to a greater height for higher 3D resolution.

Analog Design (LPB): Initial Pin Board Design

• We have chosen to start with a board that works with Braille characters.

• We are looking to modularize each 2x3 section.

• The pins will meet Braille specifications.

11”

0.2”

0.2”11”

0.1”

0.1”

0.02” to 0.05”

Distance between each Braille module = 0.15”(hor.) and 0.2”(ver.)

Analog Design : Ideas for Pin Elevation

• Magnetic Elevation (ME)• NIST ‘Pins’ down (NIST)• Temperature Sensitive Metals (TSM)

Analog Design : Magnetic Elevation

• Permanent magnets are many times stronger than the field created by current loops.

• Use Neodymium Iron Boron (NdFeB) pins wrapped in current carrying coil.

• Current in coil creates opposing magnetic field, which sends the pin up the tube.

Analog Design (ME): Pin Elevation

• Each solenoid needs around 80 wraps. To save space we put the coils on different levels.

• Can control the height of elevation using PWM.

Analog Design (ME): The Pin• Diameter of each pin

would be approximately 1/10” to 2/10”.

• Top of pin is steel (black)

• Pin rod is plastic (red)• Permanent magnet

(gray) is below, reacting to the current through the coil .

Analog Design : NIST ‘Pins’ Down

• Our hope is to be able to meet with – and – to discuss how their pin board is designed.

• If there idea is to expensive or to complex, we will see what other ideas they would have.

NIST Researchers John Roberts and Oliver Slattery

Analog Design (TSM) :

Bimetallic strip As strip is heated,

bends with highest deformation in the center.

Will cool and maintain height of pin.

Max Cohen, Hamza Aziz, Michael Amiet, Tora Unuvar, Hirotaka Fujita : Duke University : Department of Electrical and Computer Engineering

Analog Design : Ideas for Implementation

Pin Addressing High Z MUX Decoder M&M (MUX Memory)

PWM (for 3D)

Analog Design : High-Z DeMUX Decoder

• Source Decoder– On is High Voltage– Off is High Impedance

• Drain Decoder– On is Low Voltage– Off is High Impedance

• This design allows only the desired pins to activate

• Simplest solution, but may not work

• Decoder will consist of a DeMUX, Memory and Current Source

Decod

er

DecoderFPGA

Outputs

1 Z

Z

Z

0

Analog Design : M&M (MUX Memory)

• More complex then High-Z DeMUX design

• Memory will allow pins to remain elevated

• Eliminates possible problems with surrounding pins

FPGADEMUX

Memory

CurrentDriver

Outputs

Reset

Clock

Pin Grid

Analog Display Driver: PWM (for 3D)

PWM to provide capabilities of hovering pins

PWM needed because providing constant current causes pin to rise to up most position.

A transistor is our first choice for the CCVS and VCCS

PWM (UC3525)

CCVS

VCCS

Analog Design : First Prototype

Will be a 2x3 board. (one Braille character) Need to test board dimensions.

Will use magnetic elevation (ME). Need to know wrapping to current ratio. Size of pins needed.

Will use one of the pin addressing designs. Depends on if High Z MUX will perform as

expected within a reasonable cost.

Will not be connected to FPGA, will simulate FPGA output.

Analog Design : Prototype Checklist

Pin has to elevate to correct height. Record winding to current ration for correct

height.

Pin has to stay elevated at correct height for specific amount of time.

Touching our display will not cause harm to the person.

Measure current and voltage on each pin to help with interfacing of pin bed to FPGA.

Calculate magnetic field.

Analog Design : Next Steps (Prototype and Beyond)

Layout Board Record list of manufactures and stores needed. Wrapping solenoids.

Begin tests of layout board Looking specifically at:

Scrolling Pin addressing

Current Contacts to work with us Lisa Pao - CU NIST Researches of Tactile Board

John Roberts Oliver Slattery

Potential Problems

Software problems IDE learning curve FPGA/CPU communication USB debugging interface problems

Hardware Problems Current limitations Display refresh problems Interface issues

Cost Estimate

FPGA development board: $250 Computer PCB: $250 Each 2x3 pin grid module: $5 Digital-Analog Components: $100

Questions, Comments?