Electronic Guidance
Device(EGD)
Group Members
Stephen Harris
Abdul-Karim Al-Shanfari
Bradley Smethie
Robert Bornhijm
Purpose
To design a navigational aid for the blind
and vision impaired.
Objectives
To integrate with existing guidance
cane.
To provide information through audible
feedback to user about fore lying object
or sharp elevation changes.
Geographical direction is to be provided
at the user’s discretion.
Project Block Diagram
Overall Schematic
Software/Hardware Interaction
Picstart Plus
Interfaces PIC with
Computer
C-compiler
Visual Initializer
Visual Initializer (cont.)
Software Processes
Structure of:
I2C transmit (writing to SRF08)
I2C receive (reading from SRF08)
Voice chip software
I2C – Writing to Slave
Send Start Condition
Send Address of SRF08 (R/W-bit=0)
Send specific internal address of command
register
Send data byte (to specify ranging mode and
units of result)
Send Stop Condition
I2C – Reading from Slave
Send
Send
Send
Send
Send
Read
Send
Start Condition
Address of SRF08 (R/W bit = 0)
specific internal address of command register
second Start Condition
Address of SRF08 (R/W bit = 1)
the data byte off the bus
Stop Condition
Transmitter Circuit
I2C Transmit Waveform
Code outline for voice chip
Using the M0 and the M6 mode on the voice
chip we will be able to fast forward to the
correct address for the message that we are
trying to get to.
The code will generate the timing so it can
appropriately address the required sound
byte.
The code will also make sure it is in the right
addressing code.
Voice Chip Schematic
Voice chip circuit
Test Results
So far we have completed the
following:
- Communication with PIC18F452
- Simple test program – Blinking LEDs
- Recording/Playing Voice Chip
- Writing to the SRF08 module
- Documentation
Hardware and device list
Microcontroller (18F452)
Speech chip (ISD2560)
Electronic Compass (Vector 2x Compass by Precision Navigation)
Ultrasonic Devices (SRF08 Ranger by Devantech)
Battery (5V rechargeable)
Headphones (any 16 Ohm impedance headphone will do)
Volume control ( potentiometer)
Schedule and the Division of labor
Planned Deliveries
Milestone 1: Having the rangefinder and
the voice chip communicating using the
PIC
Milestone 2: Having the overall design
working and the PCB
Expo-day: Demonstrating the device
using the PCB
Contingency Plan
Most likely will switch to a I2C based
compass available from Devantech.
Current Compass requires SPI, SPI pins
on PIC already in use by I2C.
We could work around this, however an
I2C compass would be much simpler
solution.
Comments/Questions?