136 lines
4.9 KiB
C
136 lines
4.9 KiB
C
/*
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* Copyright (c) 2010, Loughborough University - Computer Science
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the Institute nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* This file is part of the Contiki operating system.
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*/
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/**
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* \file
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* Random number generator routines exploiting the cc2430 hardware
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* capabilities.
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*
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* This file overrides core/lib/random.c.
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*
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* \author
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* George Oikonomou - <oikonomou@users.sourceforge.net>
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*/
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#include "cc2430_sfr.h"
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#include "dev/cc2430_rf.h"
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/*---------------------------------------------------------------------------*/
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/**
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* \brief Generates a new random number using the cc2430 RNG.
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* \return The random number.
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*/
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unsigned short
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random_rand(void)
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{
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/* Clock the RNG LSFR once */
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ADCCON1 |= ADRCTRL0;
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return (RNDL | (RNDH << 8));
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}
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/*---------------------------------------------------------------------------*/
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/**
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* \brief Seed the cc2430 random number generator.
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* \param seed Seed value for the RNG.
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*
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* If the SEED argument is 0, seed the RNG with IF_ADC as
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* discussed in the cc2430 datasheet (rev. 2.1), section 13.11.2.2,
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* page 134. Seeding with this method should not be done during
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* normal radio operation. Thus, use this function before
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* initialising the network.
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*
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* If the SEED is provided, seed with this value instead. This will
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* result in the same sequence of random numbers each time the node
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* reboots. So, don't use it unless you have a reason (e.g. tests)
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*/
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void
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random_init(unsigned short seed)
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{
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int i;
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/* Comment out this if() block to save a nice 16 bytes of code size */
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if(seed) {
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/* If the caller provides a seed, write the high-byte first and then
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* write the low byte */
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RNDL = seed >> 8; /* High byte first */
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RNDL = seed & 0xFF;
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return;
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}
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/*
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* cc2430 Datasheet:
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* "When a true random value is required, the LFSR should be seeded by
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* writing RNDL with random values from the IF_ADC in the RF receive path."
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*
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* "To use this seeding method, the radio must first be powered on by
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* enabling the voltage regulator"
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*/
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RFPWR &= ~RREG_RADIO_PD; /* Turn on the voltage regulator */
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while(!(RFIF & IRQ_RREG_ON)); /* Wait for power up*/
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/* OK, it's powered. The respective interrupt flag has been set, clear it */
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RFIF &= ~IRQ_RREG_ON;
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/*
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* "The radio should be placed in infinite TX state, to avoid possible sync
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* detect in RX state."
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*
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* Judging by old chipcon cc2430 code examples as well as by the way cc2530
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* works, this is very likely to be "RX state" (i.e. a typo in the datasheet)
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*
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* With infinite TX, ADCTSTx always read as 0 so we'll use infinite RX
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*/
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MDMCTRL1L = 0x02; /* RX mode 10 - RX_INFINITE state */
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/* "Enter RX State - Immediate" command strobe */
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cc2430_rf_command(ISRXON);
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/* Make sure the RNG is on */
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ADCCON1 &= ~(ADRCTRL1 | ADRCTRL0);
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/* Wait for IF_ADC I-branch and Q-branch values */
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while(!(ADCTSTH & ADCTSTL));
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/* 32 times as per the chipcon example. This seems to increase randomness */
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for(i = 0; i < 32; i++) {
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/* Seed the RNG by writing into RNDL twice with values from ADCTSTx */
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RNDL = ADCTSTH;
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RNDL = ADCTSTL;
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/* Clock the RNG LSFR once */
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ADCCON1 |= ADRCTRL0;
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}
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/*
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* Exit RX state. Just shut down, network initialisation will take care of
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* properly starting the radio for us.
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*/
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RFPWR |= RREG_RADIO_PD;
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}
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