Directional Dynamic System for the Visually Impaired
ENSC 340 Project
Copyright 2003 Sound Directions
Team Organization
Farhan Ali, Team leader, CEO Daniel Kim, VP R&D Nima Jahedi, CTO Galerah Paradian, VP Marketing Ted Liu, CFO Chris Chun, COO
Overview
Market Solutions Phase one details Phase two details Questions
The Need
105,000 Canadians registered with CNIB Number is increasing by one thousand people per month Navigation aids very limited
Existing Solutions
Guide Dogs Talking Signs
IR Beacons placed in environment User Must Scan using hand-held device Line of sight required No directions given
Dynamic Directional System
Provide directions to the visually impaired based on their orientation Easy to use for the visually impaired Effective in indoor and outdoor environments Cheap
Research
Visually Impaired Program at VCC
Focus group of visually impaired navigation students
CNIB
Existing trends and technologies
Project Overview
Phase One
ENSC 340 deliverable Basic functionality
Phase Two
End of 2004
Phase One Overview
USER MODULE: Snow hill is North, Civic centre is East
Sign Module
Location code
Phase One Overview (Contd..)
Database
Wireless Communications Technology
Wireless Communications Design criteria:
Simple to integrate Short-range (within a 5 ~ 7 meter radii) Does not require line-of-sight Cheap
Competing Technologies
Infrared
Pros
Cheap, simple to integrate
Ultrasound
Cons
Complicated detection scheme Only useful in range finding Discouraged by instructors
Cons
Needs line-of-sight Narrow range communication
Competing Technologies (Contd..)
Bluetooth Pros
For short-range application
RF
Pros
Higher S/N Not line-of-sight Simple to use
Cons
Takes time to develop Expensive, development kit costs > $1,000 apiece
Cons
Co-channel Interference
Technology of our choice
Linx Technologies ES-series Evaluation Kit
Cheapest module Allows surface mount
Low interference and better S/N ratio Power consumption Signal strength indicator Usage of unlicensed ISM-band
RF Communication
RF transmitter PIC Microcontroller RF receiver PIC Microcontroller
Transmitter module
Integrated with sign module Transmit location codes for location identification Transmits at USART rate
Receiver module
Integrated with the user module Used to receive location codes Receives at USART rate
Modules Specification
Transmission Frequency Interface Data Rate Range 916.48MHz USART serial with header encapsulation Up to 200 ~ 56,000bps Approx. 500ft indoor
Range Determination
To determine if the user is near a sign When the user is near a sign
Notifies the user Receives location codes
When the user is not near a sign
Warns the user
Range Control System
Antenna
916MHz FSK
Receiver Module
RSSI
Signal Processing
PIC
When RSSI is low
The Processor is sleeping
Saves Power No UART
When RSSI is high
Interrupt The Processor wakes up
Signal Possessing
Contains:
Amplifier
Shifts the signal level Removes Spikes Stabilizing the switching against rapid triggering
Integrator Schmitt Trigger
Advantages
Processor goes to sleep
Saves Power Extends Battery Life Reduces interference from other RF sources Ensures data is only received near a sign
UART
Universal Asynchronous Receiver and Transmitter Data communication between microcontrollers and RF receiver/transmitter Frame Format: (11bits) 8-bits Data Even Parity
START Data 8-Bit Parity Bit Stop
PIC16F876A UART
- Two level FIFO register
- Used for Preamble and Location Code
- Error Flags (OERR, FERR) - Baud rate generator
Transmission
We are using 33.6K Baud Transmit Preamble and Data periodically Produce and send Parity bit
Transmitter
SEND PREAMBLE SEND DATA WAIT
Wait for a sign
Reception
After Microcontroller wakes up:
Check for errors Check for Data validity
Error
Receiver
Receive Data + parity
Check Parity Good data
Error
OERR Check Good data
Error
FERR Check
Good data
Reception (Contd..)
After receiving one byte of data:
Check if it is the preamble Check if it is old data Check if it is valid data
Error Enable location code rx
Received Data
Preamble?
Error
Old Data?
Valid Data?
Good data
Error Checking
Parity
Errors OERR FERR
1) Parity (Error in transmission)
- Done internally by the microcontroller firmware - Calculate Parity in Transmitter side - Check for parity bit on the Receiver side
Single bit checking had been used to Parity detection
Error Checking (Contd..)
2) Internal PIC microcontroller error flags for UART -OERR (Overrun error)
Third byte arrives before reading the last two
-FERR (Framing error)
Stop bit detected as clear PIC will reject data with any of the errors.
Data processing
Wait for valid location code Same code? Determine orientation Yes
Calculate resultant direction Fetch store names from database SPEAK
Determining orientation
224 North 00 32
West 192
East 64
160
South 128
96 1 0 1 1 0 0 0 1
Determine resultant direction
Resultant direction =
Store Direction User direction
Ex) London Drugs South (126) User orientation East (64) 126 - 64 = 64 EAST
Compass
Provides digital 0-255 compass bearing Uses Philips magnetic field sensor Can detect Earths magnetic field
Limitations
Magnetic interference
may influence compass reading compass should be kept afar choose sign locations with care
Tilting
tilting off horizontal results in increasing error Tilt compensated compass (upto 50 without error)
Text-to-speech
Input: ASCII ...