Smart Rover Aaron Westphal Ben Merkel Joe Merrill Mike Wissolik

Schedule

Division of Labor PIC Communications – Aaron Module Software – Mike User Interface – Ben Metal Detector Hardware - Joe

Bus Master The bus master coordinates all communication on the bus Uses I2C protocol Will auto-detect up to 15 devices Certain devices can be queried more often than others

I2C Protocol Start Condition Send Address Wait Acknowledge Send/Receive Data Byte Wait Acknowledge Send/Receive Final Byte Stop Condition

Bus Master - Initialization INIT I2C Test for Bus Operation Query address If valid add to address read buffer Increment Address This process repeats until all 15 addresses have been checked

Bus Master – Query Procedure Query Address Store Address to send data to Buffer data Address device to send to Send Data Next Address from Address Buffer

Bus Master – Query Formats Receive Data Format ADDR field contains the address of the device to send the data to If the device has no data to send the ADDR field will contain 0000 Send Data Format

Bus Master – Query Speeds Initially device will all be polled infrequently Later initial contact with device will tell bus master how often to query the device i.e. GPS does not update as frequently as RFComm

Parts Chosen GPS Trimble AG132 Compass HMR3100 Motor Control Interface with Power H- bridge using PWM signal. Metal Detector Build from scratch. RFCOMM Abacom ATRT100 – RS-232 transceiver. (Debug required)

Communication setup All communication takes place through Bus Master Communication between Host and Client slaves must be prompt as to not keep the Bus Master waiting. Each slave peripheral will be slightly different than the next. A good overall understanding of the system is necessary to design the flow chart of each peripheral.

Baseline Flow Chart

Data Flow Example 1) Bus Master Queries GPS 2) GPS responds with: Address of RFCOMM, and the most recent GPS data. 3) Bus Master relays GPS data to RFCOMM.

GPS Micro-controller Software Example (3 slides) GPS device (Trimble) updates location data about 3 to 5 times per second. GPS sentence from Trimble: “$GPRMC, ,A, ,N, ,W,000.0,0. 0,052296,15.6,E*7C” Problem: PIC cannot talk to both the Bus Master and the Trimble at the same time. (no RTOS) Solution: Bus Master will only query the GPS PIC every second or so. This gives the GPS PIC time to buffer an entire positional data sentence from the Trimble before being interrupted. GPS PIC will employ a double buffer to ensure that any data given to RFCOMM is Full and Valid.

SW example continued… Double Buffer

SW example continued… Code flow chart 1) Buffer data from the Trimble. 2) BM interrupt, read out latest full buffer to RFCOMM. 3) Buffer readout complete, go back to Buffer routine. 4) Wait until ‘new sentence’ command is sent by Trimble. Buffer pointer flags don’t change.

Smart Rover Chassis Flexy-Flyer lbs. Top speed 10 MPH Articulated chassis ATV tires Robotica Series 2 Champion Mike Konshak

Chassis: Motors Four NPC DC motors Used to drive electric wheelchairs Capable of 36V We are using 12V Don’t need the speed Want longer battery life 14.4 lbs. Each Geared down 10:1 to provide more torque and less speed.

Chassis: Body 1” squared steel tubing Capable of enduring abuse Low center of gravity Room for peripherals

Victor 883 speed controller PWM signal to determines the output current Handles 60 Amps (120 A spikes) Can be calibrated Uses a 256 bit range 128 forward/backward

Sensor: Bumper Mechanical Bumper Optical, sonar, infrared sensor can’t differentiate between obstacles. Tall grass, trash, etc. Immediate feedback from mechanical switch

Obstacle Avoidance Routine Direct Route Routine Bumper Pressed Reverse and set speed to 0. Send a flag to PC Bumper released Avoidance routine: -Turn 45º right -Move forward slowly for 3 seconds Analog Rover Circuit

Motor control circuit GP4 servo control kit by AWG GP4 unit connects to a PC or other device via RS-232 port Commands are sent at 9600 baud and in serial GP4 can output up to 8 PWM signals Extra PWM signals may be used for peripherals (camera, sensors).

Metal Detector Metal detector circuit uses two RF oscillators. Both oscillators are tuned to the exact same frequency. One oscillator provides reference frequency, frequency of second oscillator altered in the presence of metal. This is accomplished by exposing the inductor in the resonant tank of the oscillator

Metal Detector continued The resonant tank of the reference oscillator is shielded from interference. The inductor in the detector oscillator isn’t shielded, and its value changes in the presence of metal. This causes a change in frequency output by the detector oscillator.

Metal Detector continued fx fy fx-fy Output of each oscillator is sent to a mixer which produces a beat frequency fx-fy. This output is sampled by the analog to digital converter on the PIC and sent out onto the bus. A/D IIC bus

RF Communication ATRT FM Transceiver Module from Abacom. Half duplex data transmission from 9600bps to 100kbps Ranges up to 700 ft.

RF Comm. continued UARTs on PIC and PC will be used to communicate through the ATRT-100.

User Interface Development in Visual Basic.NET Display: Current information (GPS coordinates, pitch, roll, elevation, heading, speed, etc.) Controls (Desired coordinates, STOP, Metal detection ON/OFF, etc.) Back end controls and algorithms Object Avoidance Routine Heading and coordinates detection and error correction

Questions ?