Self-Contained Unit Functions Turn lights light (Light conditions pers

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Self-Contained Unit Functions Turn lights light (Light conditions pers

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AN829
Self-Contained Unit Functions Turn lights light (Light conditions persistent greater than accumulated seconds) Turn lights daylight (Light conditions persistent greater than accumulated seconds) Turn headlights after selected time after ignition (Time interval selected potentiometer) Network Functions Commanded remote master node (Body Computer, RKE, etc.) slave node Flash parking lights (n-times forever) Flash headlamps (n-times forever) added existing wiring harness without modification protocol devised address cost automotive networks. standard meant replace myriad multiplex wiring solutions current use. standard includes specification transmission protocol, transmission medium, interface between, development tools, interfaces software programming.
LightKeeper Automotive Lighting Control Module
Chuck Simmers Microchip Technology Inc.
OVERVIEW
This Application Note describes automotive exterior lighting control module using PIC16C433. This unit also communicates over Local Interconnect Network (LIN) slave controller. non-networked functions similar General Motors' Twilight Sentinel®. Networked functions allow lighting control taken over integrated body computer, remote keyless entry unit, security system.
FIGURE
SYSTEM BLOCK DIAGRAInput Conditioners Low-side Drivers Relay Parklights
Ignition
Relay
Headlights
PIC16C433
Light Sensor Delay
Relay
Bypass Light Alarm
Auxiliary Output
2002 Microchip Technology Inc.
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AN829
GENERAL DESCRIPTION
This control module provides automatic on-off control exterior lamps. will also keep exterior lamps turned preselected period time after ignition switch turned "OFF". system consists photocell, time delay rheostat with on-off switch, microcontroller module with built-in relays. Connections vehicle lamps parallel regular lamp switch connections. headlamp switch must "OFF" position allow automatic control. photocell mounted upper surface instrument panel obtain unobstructed view through windscreen. control module time delay control/on-off switch mounted adjacent headlamp switch.
Manual Lamp Operation
system turned setting time delay rheostat "OFF" position. This allows nonautomatic control exterior lamps used instead regular switch. exterior lamps desired during daylight, either methods used. Exterior lamps operated with regular headlamp switch. headlamp switch wired parallel with control module bypass system, whether rheostat "ON" "OFF". headlamp switch turned "ON", lamps will remain after ignition turned "OFF"; however, when vehicle equipped with tone alarm package, warning tone sounds reminder. photocell covered block light. This causes lamps turn still enables system turn lamps automatically when ignition turned "OFF". photocell been exposed light, time delay must elapse before lamps will turn
Automatic Operation
LightKeeper automatically switches lights sensing ambient light level. module operates automatically when ignition switch "ON", headlight switch "OFF", control rheostat "ON" position When headlamp switch "PARK" "ON", control unit powering exterior lamps instrument panel lamps, "Lights-ON" warning will function. intensity light reaching photocell decreases, resistance increases. When module senses high resistance photocell, module allows battery voltage applied headlamps, parking, side-marker, tail lamps. With headlamp dimmer switch "DIP" position, beam headlamps "ON". With headlamp dimmer switch "MAIN" position, high beam headlamps indicator "ON". intensity light reaching photocell increases, resistance decreases. When resistance enough, module turns lamps "OFF". delay timer routine module reduces chance switching lamps while passing under viaducts, trees, bright lights, other condition where lamp control wanted. move control "MAX", lights will remain approximately three minutes after engine been turned off. control "MIN", just lights will almost immediately after ignition off. This delay time changed from less than second almost three minutes.
Network Operation
network message protocol conforms Local Interconnect Network standard outlined following documents: "LIN Specification Package", Revision 1.2, November 2000 Microchip's Application Note AN729, "LIN Protocol Implementation Using Picmicro® MCUs" (DS00729) LightKeeper unit connected interface slave node. command frames interrogation frame decoded firmware. Flash parking lights (n-times forever) Flash headlamps(n-times forever) Report status bytes) these commands initiated either body computer, Remote Keyless Entry (RKE) module. identifiers have been selected this application, `0Ah' `0Bh'. Identifier `0Bh' denotes two-byte master message frame. subcommands selected first data byte following identifier `0Bh'.
DS00829A-page
2002 Microchip Technology Inc.
AN829
TABLE
Note:
COMMAND FRAMES IDENTIFIER
Action Reserved Flash Park Flash Main Used 03h-0fh Flash Number Flash Number
Data Byte Data Byte
`0Ah' identifier 8-byte slave response frame. number status bytes requested depends amount data needed master. Currently, status frame returned shown Table Notice that data bytes reserved checksum values. These data bytes will used checksum scratchpad areas three frame sizes. This allows other status fields updated without regard response frame size requested master. these fields were used storing status data, their values would over-written, master requests smaller response frame. This would require slave aware last status frame size requested rewrite corrupted data value. User status bytes currently defined, their values zeros.
(`01h' Flash Park, `02h' Flash Main). number flashes defined second data byte. Values between valid. value will cause continuous flashing. ignition should turned time, flash sequence will abort.
TABLE
STATUS 2-byte Response 4-byte Response 8-byte Response Note
STATUS RESPONSE FRAME IDENTIFIER `0Ah'
Data User Status User Status User Status Data User Status User Status User Status Data Checksum(1) used(4) Data Integral Counter Value Integral Counter Value Data Checksum(2) Data Data Data Data
System Status Flags
Delay Control Value
Light Sensor Value
used(4)
used(5)
Checksum(3)
This checksum value current 2-byte response frame. This checksum value current 4-byte response frame. This checksum value current 8-byte response frame. This checksum value from previous 2-byte response frame, valid information. This checksum value from previous 4-byte response frame, valid information. values definitions variables described above software source code.
2002 Microchip Technology Inc.
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AN829
HARDWARE
Refer Figure Module Schematics.
Output Circuits
Three high current SPDT automotive relays driven quad 1.5A Darlington low-side driver (U1). This driver interfaces level logic signals from microcontroller. driver outputs handle inductive loads, sustaining voltage Channels independently controlled PIC16C433. Channels assembled either wired-OR channels directly controlled third output. These options selected jumpers wired-OR function enabled installing
Power Supply
power supply built around automotive-grade, dropout, linear voltage regulator. internally protected from reverse polarity connection, load dump, short circuit. diodes, provide some level protection simple commercial-grade regulators used.
Input Circuits
provide input current limiting and, along with isolate analog channels from high frequency noise. Although variable resistor inputs powered from onboard referenced system ground, high speed Schottky diodes D5-7 make sure that input voltages clamped ground. constitute voltage divider reduce incoming signal from 12-14 VDC, down nominal VDC. Again, diodes (D11,12) used clamp input between ground. photocell form voltage divider reference ground, connected Analog Channel value dependent type specification chosen photocell. value selected measuring voltage total darkness full sunlight. resistor sized obtain reasonably close reading voltage rails both extremes. final voltage threshold adjusted software. delay time rheostat connected between ground (J15 J13, respectively) wiper terminal variable voltage divider connected Analog Channel switched ignition voltage connected J16.
TABLE
Jumper Driver Position Channel 2-4(1) 3-4(1) 3-5(2) BACT BACT n.c.
JUMPER
Input Source n.c. Selected Function Channel used Channel controller Channel used Channel controller Wake-up signal GP2/INT Invalid, Select
Invalid, Select Channels together Invalid, Select
Note Diodes must installed these selections. This default selection this firmware implementation.
Network Interface
interface port used alternative power connection battery. Depending capacitance specific implementation, needed, value changed. meant shunt spurious transients that occur bus.
DS00829A-page
2002 Microchip Technology Inc.
AN829
SOFTWARE
software this application composed three major sections: Main program loop, which includes: Light sensor interrogation loop Lights delay loop SLEEP routine Wake-up routine Interrupt routine Clock event scheduler
LIGHTS DELAY LOOP
After ignition been turned "OFF", check lights were "ON". they were, wait period time equal duration delay control rheostat, then turn "OFF" lights SLEEP. lights were when ignition turned "OFF", directly SLEEP.
SLEEP ROUTINE
When other events pending executed, interrupt-on-pin change setup system into power state. jump RESET vector (0000h) done when change detected port
Main Program Loop
LIGHT SENSOR INTERROGATION LOOP
While ignition switch "ON", interrogate photocell turn lights off, appropriate. ignition turned "OFF" while this loop, program falls through Lights Delay Loop.
WAKE-UP
After either RESET, wake-up from SLEEP, global initialization performed wake-up routine clears change flags. reading taken immediately from light sensor. light level lower than threshold, lights turned without time delay. program transfers control Main Light Sensor Interrogation Loop.
2002 Microchip Technology Inc.
DS00829A-page
AN829
FIGURE MAIN PROGRAM LOOP
RESET Initialization MAIN Ignition Enable Timer interrupt Ignition
WALKAWAY LightDark Disable Timer Interrupt
LightDark
DelayDuration Read Delay Timer Control
Turn Lights
Turn Lights
Time Delay
command received?
Enable Timer Interrupt
Call CheckEvents Call ProcessLINcommand Call CheckEvents
WAKE-UP Wake-up
Ignition
DelayDuration Read Delay Time Control
Read Light Sensor
Light Level Light Threshold? LightDark
Elapsed time DelayDuration
LightDark
Turn Lights
IntegralCounter 0FFh
IntegralCounter
SLEEP with Change Interrupt
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2002 Microchip Technology Inc.
AN829
Interrupt Routine
interrupt sources sorted inspecting pending interrupt flags. source interrupt timer, 16-bit system clock word incremented. source should change detection circuit, flags cleared further action taken before resuming main program execution.
Clock Event Scheduler
first test performed determine which event currently selected. main code being executed Light Sensor Interrogation routine, then system clock measured millisecond ticks. Every photocell sampled value compared threshold. light level below threshold, internal counter incremented maximum value 255. light level above threshold, counter decremented minimum LightDark when counter reaches 255, reset when counter drops continuous light condition will result state change approximately seconds. Light Delay loop being executed, system clock measured second periods. Every second internal delay count incremented then compared time duration value delay control rheostat. When delay counter equal greater than duration value, time duration cleared, indicate that required time elapsed. Control returned calling routine.
2002 Microchip Technology Inc.
DS00829A-page
AN829
FIGURE
Interrupt
INTERRUPT EVENT SCHEDULER
CheckEventTimer
Disable Interrupts Change Interrupt? Save Registers Clear Change Interrupt Flags this interrupt?
START Interrupt? Increment System Clock
Call LINHandler
elapsed?
elapsed? Read Light Sensor
Decode Process Command Frames
Increment Delay Counter
Restore Registers
Delay Counter DelayDuration Delay Elapsed Time
Light Threshold Light Level?
Return From Interrupt
Integral Counter Integral Counter
Increment IntegralCounter
Decrement IntegralCounter
Integral Counter
Clear
LightDark
Integral Counter
LightDark
Return
DS00829A-page
2002 Microchip Technology Inc.
AN829
Protocol Handling Routines
firmware that receives transmits message frame outlined flow charts Figure Handler Routine, Figure UART Routines, Figure Data Integrity Routines. This software described Microchip's Application Note AN729, "LIN Protocol Implementation Using PICmicro® MCUs (DS00729).
EXAMPLE
Given: Desired transmission rate 19.2 Kbaud TBIT 19200 FOSC MHz, FOSC Therefore: 8*52 counts. this base count added constant counts account software overhead counts propagation delay. individual time derived dividing total eight adding count delay timing routines. ((69 7.875 AUTOBAUD value actual transmission baud rate then: ((((8 (6*1 19048 baud This value lies within frequency range kHz) allowed specification.
AUTOBAUD COUNTER
signal sampled every instruction cycles. This means number counts accumulated over character time equals 8*TBIT 6TCY.
2002 Microchip Technology Inc.
DS00829A-page
AN829
FIGURE HANDLER ROUTINE
LINHandler
BREAK character complete?
AUTOBAUD AUTOBAUD
AUTOHALF AUTOHALF
START SYNC complete?
STOP complete? Increment AUTOBAUD
low?
Call RECEIVE Identifier Byte
MESSAGE_COUNTER data bytes frame
Increment COUNTER
high?
Slave transmit? Increment AUTOBAUD
TransmitMode
ReceiveMode
Call CheckParityBits Increment COUNTER Call CheckCRC (Generate Mode) COUNTER Correction Constant AUTOBAUD Call TRANSMIT (send data byte from buffer)
Call RECEIVE (get data byte from buffer)
Decrement MESSAGE_COUNTER
MESSAGE_ COUNTER
Decrement MESSAGE_COUNTER
Divide AUTOBAUD
Call CheckParityBits
AUTOHALF AUTOBAUD
MESSAGE_ COUNTER
Call CheckCRC (Verify Mode)
Return
DS00829A-page
2002 Microchip Technology Inc.
AN829
FIGURE UART ROUTINES
RECEIVE
TRANSMIT
START falling edge?
IDLE?
DelayFullBit
Call DelayHalfBit
Send START
Decrement AUTOBAUD
Call DelayFullBit
Call DelayFullBit
AUTOBAUD
Shift Received into RXTX_REG Shift Transmit RXTX_REG Return
Call DelayFullBit
Call DelayFullBit
DelayHalfBit
bits received? STOP
bits transmitted?
Decrement AUTOHALF
AUTOHALF
Send STOP
Call DelayFullBit
Call DelayFullBit
Return
Return
Return
2002 Microchip Technology Inc.
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AN829
FIGURE DATA INTEGRITY ROUTINES
CheckParityBits tempbit ID.0 ID.1 ID.2 ID.3 ID.4
CheckCRC
Data Byte from Buffer
next Data Byte from Buffer
tempbit
Data Bytes Carry
data bytes buffer done?
tempbit ID.1 ID.3 ID.4 ID.5
Return ERROR
generated?
from Buffer Data Bytes
Write Complemented Data Buffer
tempbit
result
Return
Return ERROR
Return
DS00829A-page
2002 Microchip Technology Inc.
HeadLightOUT
FIGURE
HeadLightIN
REG1 LM2937IMP-5.0
Vbat-12V
1N4004
SCHEMATICS
22uF
ParkLightOUT
HeadLight ParkLight LightON ParkLightIN
10uF
Jumper Combinations 4B-GND 4B-GP2 3B-GND 3B-GP2 BACT-GP2
1N4755
2002 Microchip Technology Inc.
LightONout LightONin 1N5819 LightAlarmCNTRL ULN2065 1N5819
ChassisGND
HeadLightCNTRL ParkLightCNTRL AuxI/O Wake-Up
CLMP1 CLMP2
MODULE SCHEMATICS
first schematic shown module itself. second typical system application.
1N5819 .005uF 1N5819 GP4/OSC2/AN3/CLKOUT GP1/AN1/Vref GP3/MCLR/Vpp GP2/T0CKI/AN2/INT VBAT
.01uF 1N4004
1N5819 .005uF 1N5819 DelayIN SensorIN
PIC16C433
VBAT LBUS BACT
.005uF
1N5819
IgnitionIN 1N5819
1N4750
Power applied unit, either from connector (JP1) and/or through individual power connections, JP3.
DS00829A-page
AN829
Chuck Simmers
Diodes relay optional circuit bypass "Lights alarm when control been assumed LightKeeper module. Depending upon characteristics, needed.
FIGURE
AN829
HeadLamp
ParkLamp
DS00829A-page
LightKeeper Ignition Battery JP1-1 JP1-2 JP1-3
SYSTEM SCHEMATIC
MAIN LIGHT
Photocell
Seat Belt Switch Seat Belt Indicator Lights Input Ignition Switch Turn Signal Input Input Ground Audio Alarm Module
Delay Time Control Dipswitch On-Off
Ignition Switch
Driver Door Jamb Switch Closed with Door Open Parking Lamp HEADLAMP HI-LO Main Beam Indicator Lamp
2002 Microchip Technology Inc.
Input from battery (+), direct Switched output ignition switch battery negative, ground, direct
AN829
FIGURE TWO-LAYER LAYOUT
Referenced Documents:
"LIN Specification Package", Revision 1.2, November 2000 Microchip's Application Note AN729, "LIN Protocol Implementation Using PICmicro® MCUs", (DS00729) "Twilight Sentinel" registered trademark General Motors Corp.
2002 Microchip Technology Inc.
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AN829
NOTES:
DS00829A-page
2002 Microchip Technology Inc.
Note following details code protection feature PICmicro® MCUs. PICmicro family meets specifications contained Microchip Data Sheet. Microchip believes that family PICmicro microcontrollers most secure products kind market today, when used intended manner under normal conditions. There dishonest possibly illegal methods used breach code protection feature. these methods, knowledge, require using PICmicro microcontroller manner outside operating specifications contained data sheet. person doing engaged theft intellectual property. Microchip willing work with customer concerned about integrity their code. Neither Microchip other semiconductor manufacturer guarantee security their code. Code protection does mean that guaranteeing product "unbreakable". Code protection constantly evolving. Microchip committed continuously improving code protection features product.
have further questions about this matter, please contact local sales office nearest you.
Information contained this publication regarding device applications like intended through suggestion only superseded updates. your responsibility ensure that your application meets with your specifications. representation warranty given liability assumed Microchip Technology Incorporated with respect accuracy such information, infringement patents other intellectual property rights arising from such otherwise. Microchip's products critical components life support systems authorized except with express written approval Microchip. licenses conveyed, implicitly otherwise, under intellectual property rights.
Trademarks Microchip name logo, Microchip logo, FilterLab, KEELOQ, microID, MPLAB, PIC, PICmicro, PICMASTER, PICSTART, MATE, SEEVAL Embedded Control Solutions Company registered trademarks Microchip Technology Incorporated U.S.A. other countries. dsPIC, ECONOMONITOR, FanSense, FlexROM, fuzzyLAB, In-Circuit Serial Programming, ICSP, ICEPIC, microPort, Migratable Memory, MPASM, MPLIB, MPLINK, MPSIM, MXDEV, PICC, PICDEM, PICDEM.net, rfPIC, Select Mode Total Endurance trademarks Microchip Technology Incorporated U.S.A. Serialized Quick Turn Programming (SQTP) service mark Microchip Technology Incorporated U.S.A. other trademarks mentioned herein property their respective companies. 2002, Microchip Technology Incorporated, Printed U.S.A., Rights Reserved.
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2002 Microchip Technology Inc.
DS00829A page
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Self-Contained Unit Functions Turn lights light (Light conditions pers

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