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.
Software/Hardware Interaction • Picstart Plus Interfaces PIC with Computer • C-compiler
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 Start Condition • Send Address of SRF08 (R/W bit = 0) • Send specific internal address of command register • Send second Start Condition • Send Address of SRF08 (R/W bit = 1) • Read the data byte off the bus • Send Stop Condition
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.
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)
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.