Remote Access Control

main.c File Reference

---

Detailed Description

Main application source file.

This file contains the setup and main control code for the Remote Keyless Entry application.

• File: main.c
• Compiler: IAR EWAVR 4.11B
• Supported devices: ATtiny45/85
• AppNote: AVR411 - Secure Rolling Code Algorithm for Wireless Link

Author:

Atmel Corporation: http://www.atmel.com
Support email: avr@atmel.com

Name

Revision

1206

Date

2006-11-08 09:50:32 +0100 (on, 08 nov 2006)

Copyright (c) 2006, Atmel Corporation All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

3. The name of ATMEL may not be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY ATMEL ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE EXPRESSLY AND SPECIFICALLY DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Definition in file main.c.

#include "common.h"
#include "config.h"
#include "aes.h"
#include "cmac.h"
#include "memory.h"
#include "comms.h"
#include "crc.h"

Include dependency graph for main.c:

Go to the source code of this file.

Functions
void	errorLoop (byte blinkCount)
void	handleResetFlags (void)
void	main (void)
static __interrupt void	pinChangeHandler (void)
void	setupPeripherals (void)
COMMAND_CODE_TYPE	sleepAndGetCommand (void)
void	transmitCommandMessage (COMMAND_CODE_TYPE command)
void	transmitTeachMessage (void)

---

Function Documentation

void errorLoop

(

byte

blinkCount

)

Loop forever, blinking a LED.

Definition at line 128 of file main.c.

Referenced by handleResetFlags().

{
        // Initialize Watchdog Timer.
        __watchdog_reset();
        WDTCR = (1<<WDCE) | (1<<WDE);
        WDTCR = (1<<WDCE) | (1<<WDE) | (1<<WDP3) | (1<<WDP0);
        WDTCR |= (1<<WDTIF) | (1<<WDTIE);

        // Enable Power Down Sleep Mode.
        MCUCR = (1<<SE) | (1<<SM1) | (0<<SM0);

        // Start blinking.
        __enable_interrupt();
        DDRB = (1<<PB3);
        PORTB = (0<<PB3);
        for(;;) {
                __sleep();
                __watchdog_reset();
                WDTCR |= (1<<WDTIE);
                byte blinks;
                for( blinks = 0; blinks < blinkCount; ++blinks ) {
                        PORTB = (1<<PB3);
                        __delay_cycles( (8000000/1000)*50 ); // 50ms
                        PORTB = (0<<PB3);
                        __delay_cycles( (8000000/1000)*50 ); // 50ms
                }
        }
}

void handleResetFlags

(

void

)

Read reset flags and act accordingly.

Definition at line 254 of file main.c.

References errorLoop(), and MAX_WATCHDOG_RESETS.

Referenced by main().

{
#ifndef NOWDT
        static __no_init byte __eeprom watchdogResetCount; // Will be set to 0 or 0xff on first Power-up.
        if( watchdogResetCount == 0xff ) {
                watchdogResetCount = 0x00;
        }
#endif

        // Read and clear reset flags.
        byte resetFlags = MCUSR;
        MCUSR = 0x00;

        // Check for reset sources.
        if( resetFlags & ((1<<PORF)|(1<<EXTRF)) ) { // Power-on or External Reset?
#ifndef NOWDT
                watchdogResetCount = 0;
#endif
        }
#ifndef NOWDT
        if( resetFlags & (1<<WDRF) ) { // Watchdog Reset?
                if( watchdogResetCount >= MAX_WATCHDOG_RESETS ) {
                        errorLoop( 2 );
                } else {
                        ++watchdogResetCount;
                }
        }
#endif
#ifndef NOBOD   
        if( resetFlags & (1<<BORF) ) { // Brown Out Reset?
                errorLoop( 1 );
        }
#endif
}

Here is the call graph for this function:

void main

(

void

)

Definition at line 324 of file main.c.

References calcCMACSubkey(), calcKeySchedule(), COMMAND_CODE_TYPE, cryptoBlock, handleResetFlags(), initializeMessage(), setupPeripherals(), sleepAndGetCommand(), TEACH_COMMAND, transmitCommandMessage(), and transmitTeachMessage().

{
        handleResetFlags();
        setupPeripherals();
        initializeMessage();
        calcKeySchedule( secretKey );
        calcCMACSubkey( cryptoBlock );
        __enable_interrupt();

        for(;;) { // Loop for ever.

                PORTB &= ~(1<<PB4); // Disable transmitter.
                DDRB &= ~(1<<PB1); // PB1 back to input for button input.

                COMMAND_CODE_TYPE command = sleepAndGetCommand();

                PORTB |= (1<<PB4); // Enable transmitter.
                DDRB |= (1<<PB1); // PB1 to output for both ASK and FSK.

                // Allow time for transmitter to start up.
                __delay_cycles( 8000000 / 1000 * 5 ); // 5ms, given in datasheet.

                if( command != TEACH_COMMAND ) {
                        transmitCommandMessage( command );
                } else {
                        transmitTeachMessage();
                }
        }
}

Here is the call graph for this function:

static __interrupt void pinChangeHandler

(

void

)

[static]

ISR called when a button is pressed.

Definition at line 60 of file main.c.

References BUTTON_MASK, and COMMAND_CODE_TYPE.

{
        COMMAND_CODE_TYPE lastButtonState;
        COMMAND_CODE_TYPE newButtonState;
        unsigned char equalCount = 0;

        lastButtonState = PINB & BUTTON_MASK;
        do {
                __delay_cycles( 8000 ); // Allow for debounce and human slowness. Empirical value.
                newButtonState = PINB & BUTTON_MASK;
                if( newButtonState == lastButtonState ) {
                        ++equalCount;
                } else {
                        equalCount = 0;
                        lastButtonState = newButtonState;
                }
        } while( equalCount < 10 ); // 10 is empirical value.
}

void setupPeripherals

(

void

)

Initial setup of misc. peripherals in the AVR.

Definition at line 292 of file main.c.

References BUTTON_MASK.

Referenced by main().

{
#ifndef NOWDT
        // Initialize Watchdog Timer.
        __watchdog_reset();
        WDTCR = (1<<WDCE) | (1<<WDE);
        WDTCR = (1<<WDCE) | (1<<WDE) | (1<<WDP3) | (1<<WDP0);
        WDTCR |= (1<<WDIF) | (1<<WDIE);
#endif

        // Setup Pin-change input mask.
        PCMSK = BUTTON_MASK;

        // Setup IO ports.
        PORTB = (0<<PB0) |
                (0<<PB1) |
                (0<<PB2) |
                (0<<PB3) |
                (0<<PB4) |
                (0<<PB5);
        DDRB |= (1<<PB4); // Transmitter Enable signal is output.

        // Turn off unused modules to save power/oomph.
        ACSR |= (1<<ACD);
        PRR = (1<<PRTIM1) | (1<<PRADC);

        // Enable Power Down Sleep Mode.
        MCUCR = (1<<SE) | (1<<SM1) | (0<<SM0);
}

COMMAND_CODE_TYPE sleepAndGetCommand

(

void

)

Sleep and wait for button to be pressed.

Definition at line 93 of file main.c.

References BUTTON_MASK, and COMMAND_CODE_TYPE.

Referenced by main().

{
        COMMAND_CODE_TYPE buttonState;

        // Enable Power Down Sleep Mode.
        MCUCR = (1<<SE) | (1<<SM1) | (0<<SM0);

        // Enable Pin Change Interrupt.
        __delay_cycles( 100 ); // Wait for RF TX ctrl pins to settle. Empirical value.
        GIFR |= (1<<PCIF);
        GIMSK |= (1<<PCIE);

        do {
#ifndef NOWDT
                // Restart watchdog if it timed out.
                if( !(WDTCR & (1<<WDIE)) ) {
                        __watchdog_reset();
                        WDTCR |= (1<<WDIE);
                }
#endif
                __sleep(); // Wait for Pin-Change Interrupt.

                // Read pins and mask out unused inputs according pin change mask.
                buttonState = PINB & BUTTON_MASK;
        } while( !buttonState );

        GIMSK &= ~(1<<PCIE); // Good practice to turn off interrupt.

        return buttonState;
}

void transmitCommandMessage

(

COMMAND_CODE_TYPE

command

)

Construct and transmit and ordinary command message.

Definition at line 160 of file main.c.

References calcCMAC(), continueTransmission(), createMessage(), cryptoBlock, MAC_BYTES, SharedBlock::messagePayload, PREBURST_BYTES, MessagePayload::serialNo, sharedBlock, startCounterUpdate(), startTransmission(), stopTransmission(), waitForCounterUpdate(), and waitForTransmission().

Referenced by main().

{
        const byte preburst = 0xff;
        byte i;

        createMessage( command );
        startTransmission( &preburst, 1 );
        for( i = 0; i < PREBURST_BYTES-1; ++i ) {
                waitForTransmission();
                continueTransmission( &preburst, 1 );
        }
        waitForTransmission();
        continueTransmission( (const byte *)
                        &sharedBlock.messagePayload,
                        sizeof( struct MessagePayload ) );
        calcCMAC( (const byte *)
                        &sharedBlock.messagePayload.serialNo,
                        cryptoBlock );
        waitForTransmission();
        
        // Send MAC bytes and one extra byte to make sure all Manchester edges are recognized
        // at the receiver. Actually only one extra edge after the last MAC byte would be enough,
        // but it is more convenient to just add another byte in the transmission.
        cryptoBlock[ MAC_BYTES ] = 0x00; // Don't reveal more MAC bytes than necessary.
        continueTransmission( cryptoBlock, MAC_BYTES + 1 );

        startCounterUpdate();
        waitForTransmission();
        stopTransmission();
        waitForCounterUpdate();
}

Here is the call graph for this function:

void transmitTeachMessage

(

void

)

Construct and transmit a message with serial number, encrypted key etc.

Definition at line 195 of file main.c.

References BLOCK_SIZE, calcCRC(), calcKeySchedule(), cipherLookup(), continueTransmission(), copyBytesFromEEPROM(), CRCReg, SharedBlock::cryptoBlock, cryptoBlock, initCRC(), initializeMessage(), KEY_SIZE, SharedBlock::messagePayload, PREBURST_BYTES, SEQ_COUNTER_BYTES, SERIAL_NO_BYTES, MessagePayload::serialNo, sharedBlock, startTransmission(), stopTransmission(), and waitForTransmission().

Referenced by main().

{
        const byte preburst = 0xff;
        byte i;

        calcKeySchedule( sharedKey );
        initCRC();
        startTransmission( &preburst, 1 );
        for( i = 0; i < PREBURST_BYTES-1; ++i ) {
                waitForTransmission();
                continueTransmission( &preburst, 1 );
        }
        waitForTransmission();
        continueTransmission( (const byte*)
                        &sharedBlock.messagePayload,
                        SERIAL_NO_BYTES + SEQ_COUNTER_BYTES + 1 );
        for( i = 0; i < SERIAL_NO_BYTES + SEQ_COUNTER_BYTES; ++i ) {
                calcCRC( ((byte *) &sharedBlock.messagePayload.serialNo)[ i ] );
        }
        copyBytesFromEEPROM( cryptoBlock,
                        secretKey, BLOCK_SIZE );
        cipherLookup( cryptoBlock );
        waitForTransmission();
        continueTransmission( cryptoBlock, BLOCK_SIZE );
        for( i = 0; i < BLOCK_SIZE; ++i ) {
                calcCRC( cryptoBlock[ i ] );
        }
#if KEY_SIZE > BLOCK_SIZE
        copyBytesFromEEPROM( sharedBlock.cryptoBlock,
                        secretKey + BLOCK_SIZE,
                        KEY_SIZE - BLOCK_SIZE );
#if KEY_SIZE < (2*BLOCK_SIZE)

        for( i = KEY_SIZE - BLOCK_SIZE; i < BLOCK_SIZE; ++i ) {
                sharedBlock.cryptoBlock[ i ] = 0x00;
        }
#endif
        cipherLookup( sharedBlock.cryptoBlock );
        waitForTransmission();
        continueTransmission( sharedBlock.cryptoBlock,
                        BLOCK_SIZE );
        for( i = 0; i < BLOCK_SIZE; ++i ) {
                calcCRC( sharedBlock.cryptoBlock[ i ] );
        }
#endif

        calcCRC( 0x00 );
        calcCRC( 0x00 );
        waitForTransmission();
        continueTransmission( CRCReg, 3 ); // Transmit one extra byte, see comment for MAC transmission in transmitCommandMessage(...).
        calcKeySchedule( secretKey );
        initializeMessage();
        waitForTransmission();
        stopTransmission();
}

Here is the call graph for this function: