contiki/cpu/cc253x/dev/random.c

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/*
* Copyright (c) 2011, George Oikonomou - <oikonomou@users.sourceforge.net>
* 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. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``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 DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS 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.
*
* This file is part of the Contiki operating system.
*/
/**
* \file
* Random number generator routines exploiting the cc2530 hardware
* capabilities.
*
* This file overrides core/lib/random.c.
*
* \author
* George Oikonomou - <oikonomou@users.sourceforge.net>
*/
#include "cc253x.h"
#include "sfr-bits.h"
#include "dev/cc2530-rf.h"
/*---------------------------------------------------------------------------*/
/**
* \brief Generates a new random number using the cc253x RNG.
* \return The random number.
*/
unsigned short
random_rand(void)
{
/* Clock the RNG LSFR once */
ADCCON1 |= ADCCON1_RCTRL0;
return (RNDL | (RNDH << 8));
}
/*---------------------------------------------------------------------------*/
/**
* \brief Seed the cc253x random number generator.
* \param seed Ignored. It's here because the function prototype is in core.
*
* We form a seed for the RNG by sampling IF_ADC as
* discussed in the user guide.
* Seeding with this method should not be done during
* normal radio operation. Thus, use this function before
* initialising the network.
*/
void
random_init(unsigned short seed)
{
int i;
/* Make sure the RNG is on */
ADCCON1 &= ~(ADCCON1_RCTRL1 | ADCCON1_RCTRL0);
/* Infinite RX */
FRMCTRL0 = FRMCTRL0_RX_MODE1;
/* Turn RF on */
CC2530_CSP_ISRXON();
/* Wait until (user guide sec. 23.12, p 239) "the chip has been in RX long
* enough for the transients to have died out. A convenient way to do this is
* to wait for the RSSI-valid signal to go high." */
while(!(RSSISTAT & RSSISTAT_RSSI_VALID));
/*
* Form the seed by concatenating bits from IF_ADC in the RF receive path.
* Keep sampling until we have read at least 16 bits AND the seed is valid
*
* Invalid seeds are 0x0000 and 0x8003 - User Guide (sec. 14.2.2 p. 146):
* "Note that a seed value of 0x0000 or 0x8003 always leads to an unchanged
* value in the LFSR after clocking, as no values are pushed in via in_bit
* (see Figure 14-1); hence, neither of these seed values should not be used
* for random-number generation."
*/
i = 0;
while(i < 16 || (seed == 0x0000 || seed == 0x8003)) {
seed = (seed << 1) | (RFRND & RFRND_IRND);
seed <<= 1;
i++;
}
/* High byte first */
RNDL = seed >> 8;
RNDL = seed & 0xFF;
/* RF Off. NETSTACK_RADIO.init() will sort out normal RF operation */
CC2530_CSP_ISRFOFF();
}