ECE 477 Design Review Team 4  Fall 2010 (L to R) Andy Sydelko, Chris Cadawallader, Mike Wiliams, Craig Pilcher

Outline Project overview Project-specific success criteria Block diagram Component selection rationale Packaging design Schematic and theory of operation PCB layout Software design/development status Project completion timeline Questions / discussion

Project Overview - Motivation “A child safety-system that prevents parents and caretakers from accidentally leaving children in vehicles.” Average number of U.S. child hyperthermia fatalities per year since 1998: 37  41 so far in 2010 alone Our goal is to prevent as many deaths as possible If the caretaker cannot be warned, the child protection system will try to act on its own Extensible, could be modified for other uses, e.g. pets or seat belt verification on a school bus

Project Specific Success Criteria An ability to determine the operating state of the vehicle via the OBD-II port An ability to determine the presence of a child in a safety seat An ability to use multiple safety seats in one vehicle An ability to sound an audible alarm when the ignition is turned off An ability to interface directly to the internal vehicle CAN

Block Diagrams – Car Side

Block Diagram – Child Side

Component Selection Rationale - Micro Extensive onboard peripherals are available  Multiple CAN ports, PWM for audio output, ATD converters, dual SCI ports, timers, etc. Large amounts of available flash (512KB) for audio sample storage Controllable power consumption –Effectively battery powered when the car is off Cost – expensive, but perfect for this stage –Eventual goal is to scale down to the smallest 9S12(X) that handles all peripheral, total audio samples, and speed requirements

Component Selection Rationale – RF XCVRs Built-in pairing support Long range (up to 1km), allows the use of small, inefficient antennas Transmitter only powered when sending switch states  Critical for battery-powered child side  Receiver enters low-power polling state when not receiving Transceiver/Encoder pair operate with a microcontoller Extra input pins for future expansion  8 inputs = 256 possible status messages

Packaging Design – Car Side Car side box contains:  16-pin OBD-II cable  RS-232 connector  Two buttons (learn, reset)  Two LEDs (power, learning)  Speaker Also needs to mount easily under dash or near OBD-II port

Child Side Child side box will have 1 LED (power) and 1 button (learn) and a port for child detection device To be replaced for integration with specific devices Child side box must have access for battery replacement

General Schematic/Theory of Operation 2 CAN ports – Vehicle communication  High-speed CAN compatibility for vehicle state detection and unusual vehicles  Single-wire CAN for peripheral control, such as windows, alarm, etc. 2 SCI ports – RS232 (debugging) and RF RX 2 ATD – Car state detection for older OBD-II protocols PWM – Audio Output 11 GPIO – Control lines/DEBUG/DEC data, switch inputs

RF Decoder Decoder polls receiver to check for any incoming packets Baud rate tied to ground, same as encoder High transmission speed is irrelevant Digital outputs routed directly to microcontroller Learn button is now debounced through the microcontroller, which also allows the micro to track if we are in the “Learning state” and activate an audio confirmation when a seat is added.

SWCAN Transceiver Sits on SWCAN bus, speed controlled via microcontroller Circuitry simply as required by the transceiver Powered by the cars battery directly Can enter sleep mode where it is woken by SWCAN activity Responsible for rolling down windows, activating panic on most vehicles

Child Side – Theory of Operation

- Encoder sends button events to the transmitter - All button events tied to send function - Reduces power consumption to only when transmitting - “Change ID” button for the one in 2^20 chances of a conflict (probably useless) - Encoder connected directly to transmitter, power down line keeps transmitter off when buttons not being pressed - Status indication LED shows when ID generation is taking place

Car Side Layout – General Considerations RF Isolation is important Accurate clock sources are important for high-speed CAN communication Extensive debugging access and expandability Need multiple power supplies: –5V for most chips –3.3V for RF decoder –12V for SWCAN transceiver

Child Side Layout - General Considerations Two boards completed Important considerations  Remove ground plane from Antenna  Bring extra inputs to headers for expanding system Future improvements:  Debounce learn switch  Make sure to bring Vcc  Change antenna drill hole sizes

Microcontroller Layout Considerations Very specific oscillator layout required for accurate crystal operation. –Current layout should exceed Freescale recommendations Extensive bypass capacitors needed for power supplies, PLL, voltage reference for ATD converters, and internal 2.5V supply.

PCB - RF and Power Supply Considerations Short, low-impedance connection to the antenna No planes or traces under the decoder or antenna –Ground plane recommended for the receiver Receiver requires very clean, 3.3V power supply  Designed to operate from a battery with no bypass capacitors  Utilizes input filtering and resistance to reduce and clean supply to necessary levels Linear regulator chosen on car-side as a result of noise considerations

Software Design/Development Status Test Software Features - PWM audio output test - CAN debugging routines - Generic digital port dumps - ATD converter test Operational Software - Detection of cars on older protocols completed - Tracking of child seats state working with ID reception - Vehicle status state machine that integrates multiple protocols and seat tracking working - Audio output not start - Vehicle action via CAN not started

Project Completion Timeline TaskTimeline Final PCB Layout CheckOctober 20, 2010 PCB Fabrication~November 1 Car Detection Software via ATDOctober 22 CAN Decoding SoftwareOctober 29 Audio Warning System SoftwareNovember 5 PCB TestingNovember 16 PackagingDecember 1

Questions / Discussion