Remote Access Control

comms.h File Reference

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Detailed Description

Header file for communications public functions.

This file contains the prototypes for the communications control functions. The implementation is found in the comms.c file. The communication is interrupt-controlled and is initiated with the startTransmission() function. To add more data to the transmission before it has finished, use the continueTransmission() function. To wait for an ongoing transmission to finish, use the waitForTransmisssion() function. Always call the stopTransmission() function when you do not want to transmit more data. This turns off the RF transmitter.

• File: comms.h
• 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

1193

Date

2006-10-31 14:21:08 +0100 (ti, 31 okt 2006)

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

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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 comms.h.

#include "common.h"
#include "config.h"

Include dependency graph for comms.h:

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Functions
void	continueTransmission (const byte *buffer, byte byteCount)
void	startTransmission (const byte *buffer, byte byteCount)
void	stopTransmission ()
void	waitForTransmission ()

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Function Documentation

void continueTransmission	(	const byte *	buffer,
		byte	byteCount
	)

Add 'byteCount' bytes from 'buffer' in SRAM to an already running transmission.

Definition at line 338 of file comms.c.

References nextUSIByte, and USIBytesLeft.

Referenced by transmitCommandMessage(), and transmitTeachMessage().

{
        // Prepare control variables.
        byte currentByte = *buffer++;
        nextUSIByte = buffer;
        USIBytesLeft = byteCount;

        // Prepare Manchester pattern.
        byte manchesterByte1 = manchesterNibble[ currentByte >> 4 ];
        byte manchesterByte2 = manchesterNibble[ currentByte & 0x0f ];

        // Put bit 0-6 of pattern at the end of USI data register.
        USIDR = USIDR & 0x80 | (manchesterByte1 >> 1);

        // Prepare part two of pattern, ie. bits 6-13.
        manchesterPartTwo = (manchesterByte1 << 6) | (manchesterByte2 >> 2);

        // Prepare part three of pattern, ie. bits 13-15 and 5 dummy zero bits.
        manchesterPartThree = (manchesterByte2 << 5);

        // Enable USI interrupts again.
        USICR |= (1<<USIOIE);
}

void startTransmission	(	const byte *	buffer,
		byte	byteCount
	)

Start transmitting 'byteCount' bytes from 'buffer' in SRAM using Manchester encoding.

Definition at line 266 of file comms.c.

References nextUSIByte, and USIBytesLeft.

Referenced by transmitCommandMessage(), and transmitTeachMessage().

{
        // Prepare control variables.
        byte currentByte = *buffer++;
        nextUSIByte = buffer;
        USIBytesLeft = byteCount;

        // Prepare Manchester pattern.
        byte manchesterByte1 = manchesterNibble[ currentByte >> 4 ];
        byte manchesterByte2 = manchesterNibble[ currentByte & 0x0f ];

        // Put idle bit value and bit 0-6 of pattern in USI data register.
        // This is the first part of the pattern. The output pin changes immediately.
        USIDR = 0x80 | (manchesterByte1 >> 1);

        // Prepare part two of pattern, ie. bits 6-13.
        manchesterPartTwo = (manchesterByte1 << 6) | (manchesterByte2 >> 2);

        // Prepare part three of pattern, ie. bits 13-15 and 5 dummy zero bits.
        manchesterPartThree = (manchesterByte2 << 5);

        // Clear overflow flag and seed USI timer
        // to overflow in 7 bit shifts, so that last bit of first part of pattern is left.
        USISR = (1<<USIOIF) | (16-7);

        // Start USI in Three-wire mode clocked by
        // Timer/Counter0 Compare Match A. Overflow interrupt enabled.
  #ifdef ASK
        USICR = (1<<USIOIE) |
                (0<<USIWM1) | (1<<USIWM0) |   // Three-wire mode, data output on PB1.
                (0<<USICS1) | (1<<USICS0);
  #endif
  #ifdef FSK
        USICR = (1<<USIOIE) |
                (1<<USIWM1) | (0<<USIWM0) |   // Two-wire mode, data output on PB0 (open collector).
                (0<<USICS1) | (1<<USICS0);
        DDRB |= (1<<PB0); // Enable data line output open collector driver.
        PORTB |= ((1<<PB1) | (1<<PB0)); // Turn on carrier wave and give data line to USI module.
  #endif

  #ifdef BPS_19200
        // Set data rate to 19200 bps (ie. 9600 bps with Manchester).
        TCNT0 = 0x00;
        OCR0A = 51; // approx. (8MHz/8/19200bps)-1, ref. CTC Mode in datasheet.
        TCCR0A = (1<<WGM01); // Clear on Compare Match.
        TCCR0B = (0<<CS02) | (1<<CS01) | (0<<CS00); // Prescaler factor 8.
  #endif
  #ifdef BPS_9600
        // Set data rate to 9600 bps (ie. 4800 bps with Manchester).
        TCNT0 = 0x00;
        OCR0A = 103; // approx. (8MHz/8/9600bps)-1, ref. CTC Mode in datasheet.
        TCCR0A = (1<<WGM01); // Clear on Compare Match.
        TCCR0B = (0<<CS02) | (1<<CS01) | (0<<CS00); // Prescaler factor 8.
  #endif
  #ifdef BPS_4800
        // Set data rate to 4800 bps (ie. 2400 bps with Manchester).
        TCNT0 = 0x00;
        OCR0A = 25; // approx. (8MHz/64/2400bps)-1, ref. CTC Mode in datasheet.
        TCCR0A = (1<<WGM01); // Clear on Compare Match.
        TCCR0B = (0<<CS02) | (1<<CS01) | (1<<CS00); // Prescaler factor 64.
  #endif
  #ifdef BPS_2400
        // Set data rate to 2400 bps (ie. 1200 bps with Manchester).
        TCNT0 = 0x00;
        OCR0A = 51; // approx. (8MHz/64/2400bps)-1, ref. CTC Mode in datasheet.
        TCCR0A = (1<<WGM01); // Clear on Compare Match.
        TCCR0B = (0<<CS02) | (1<<CS01) | (1<<CS00); // Prescaler factor 64.
  #endif
}

void stopTransmission

(

)

Stop transmission module and restore previous port states.

Definition at line 368 of file comms.c.

Referenced by transmitCommandMessage(), and transmitTeachMessage().

{
        USICR = 0x00;
  #ifdef FSK
        PORTB &= ~((1<<PB1) | (1<<PB0)); // Turn off carrier wave and release data line.
        DDRB &= ~(1<<PB0); // Disable data line output open collector driver.
  #endif
}

void waitForTransmission

(

)

Sleep and wait for a running transmission to finish.

Definition at line 379 of file comms.c.

References USIBytesLeft.

Referenced by transmitCommandMessage(), and transmitTeachMessage().

{
        // Enter Idle sleep mode while waiting for transmission to finish.
        MCUCR = (1<<SE) | (0<<SM1) | (0<<SM0);
        while( USIBytesLeft ) { __sleep(); }
}