nes-proj/cpu/cc2538/dev/random.c

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/*
* Copyright (c) 2012, Texas Instruments Incorporated - http://www.ti.com/
* 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 copyright holder 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 COPYRIGHT HOLDERS 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
* COPYRIGHT HOLDER 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.
*/
/**
* \addtogroup cc2538
* @{
*
* \defgroup cc2538-random cc2538 Random Number Generator
*
* Driver for the cc2538 Hardware Random Number Generator
* @{
*
* \file
* Random number generator routines exploiting the cc2538 hardware
* capabilities.
*
* This file overrides core/lib/random.c.
*/
#include "contiki.h"
#include "dev/rfcore.h"
#include "dev/cc2538-rf.h"
#include "dev/soc-adc.h"
#include "dev/sys-ctrl.h"
#include "reg.h"
/*---------------------------------------------------------------------------*/
/**
* \brief Generates a new random number using the cc2538 RNG.
* \return The random number.
*/
unsigned short
random_rand(void)
{
uint32_t rv;
/* Clock the RNG LSFR once */
REG(SOC_ADC_ADCCON1) |= SOC_ADC_ADCCON1_RCTRL0;
rv = REG(SOC_ADC_RNDL) | (REG(SOC_ADC_RNDH) << 8);
return ((unsigned short)rv);
}
/*---------------------------------------------------------------------------*/
/**
* \brief Seed the cc2538 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.
*
* \note Must not be called after the RF driver has been initialised and is
* in normal operation. If it is absolutely necessary to do so, the
* radio will need re-initialised.
*/
void
random_init(unsigned short seed)
{
int i;
unsigned short s = 0;
/* Make sure the RNG is on */
REG(SOC_ADC_ADCCON1) &= ~(SOC_ADC_ADCCON1_RCTRL1 | SOC_ADC_ADCCON1_RCTRL0);
/* Enable clock for the RF Core */
REG(SYS_CTRL_RCGCRFC) = 1;
/* Wait for the clock ungating to take effect */
while(REG(SYS_CTRL_RCGCRFC) != 1);
/* Infinite RX - FRMCTRL0[3:2] = 10
* This will mess with radio operation - see note above */
REG(RFCORE_XREG_FRMCTRL0) = 0x00000008;
/* Turn RF on */
CC2538_RF_CSP_ISRXON();
/*
* Wait until "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(!(REG(RFCORE_XREG_RSSISTAT) & RFCORE_XREG_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 and should not be used.
*/
while(s == 0x0000 || s == 0x8003) {
for(i = 0; i < 16; i++) {
s |= (REG(RFCORE_XREG_RFRND) & RFCORE_XREG_RFRND_IRND);
s <<= 1;
}
}
/* High byte first */
REG(SOC_ADC_RNDL) = (s >> 8) & 0x00FF;
REG(SOC_ADC_RNDL) = s & 0xFF;
/* RF Off. NETSTACK_RADIO.init() will sort out normal RF operation */
CC2538_RF_CSP_ISRFOFF();
}
/**
* @}
* @}
*/