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103 lines
2.4 KiB
C
103 lines
2.4 KiB
C
/*
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* Copyright (C) 2014 Loci Controls Inc.
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*
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* This file is subject to the terms and conditions of the GNU Lesser
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* General Public License v2.1. See the file LICENSE in the top level
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* directory for more details.
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*/
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/**
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* @ingroup driver_periph
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* @{
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*
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* @file
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* @brief Low-level random number generator driver implementation
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*
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* @author Ian Martin <ian@locicontrols.com>
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*
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* @}
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*/
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#include <stdint.h>
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#include "cpu.h"
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#include "periph_conf.h"
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#include "periph/random.h"
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/* only compile this driver if enabled in the board's periph_conf.h */
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#if RANDOM_NUMOF
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void random_init(void)
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{
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uint16_t seed = 0;
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int i;
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/* Make sure the RNG is on */
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SOC_ADC->cc2538_adc_adccon1.ADCCON1bits.RCTRL = 0;
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/* Enable clock for the RF Core */
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SYS_CTRL_RCGCRFC = 1;
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/* Wait for the clock ungating to take effect */
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while (SYS_CTRL_RCGCRFC != 1);
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/* Infinite RX - FRMCTRL0[3:2] = 10. This will mess with radio operation */
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RFCORE_XREG_FRMCTRL0 = 0x00000008;
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/* Turn RF on */
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RFCORE_SFR_RFST = ISRXON;
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/*
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* Wait until "the chip has been in RX long enough for the transients to
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* have died out. A convenient way to do this is to wait for the RSSI-valid
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* signal to go high."
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*/
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while (!RFCORE->cc2538_rfcore_xreg_rssistat.XREG_RSSISTATbits.RSSI_VALID);
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/*
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* Form the seed by concatenating bits from IF_ADC in the RF receive path.
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* Keep sampling until we have read at least 16 bits AND the seed is valid
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*
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* Invalid seeds are 0 and 0x8003 and should not be used.
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*/
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for (i = 0; (i < 8) || (seed == 0) || (seed == 0x8003); i++) {
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seed <<= 2;
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seed ^= RFCORE->cc2538_rfcore_xreg_rfrnd.XREG_RFRND;
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}
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/* Seed the high byte first: */
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SOC_ADC_RNDL = (seed >> 8) & 0xff;
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SOC_ADC_RNDL = seed & 0xff;
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/* Turn RF off: */
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RFCORE_SFR_RFST = ISRFOFF;
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random_poweron();
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}
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int random_read(char *buf, unsigned int num)
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{
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unsigned count;
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for (count = 0; count < num; ) {
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/* Clock the RNG LSFR once: */
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SOC_ADC->cc2538_adc_adccon1.ADCCON1bits.RCTRL = 1;
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/* Read up to 2 bytes of random data: */
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buf[count++] = SOC_ADC_RNDL;
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if (count >= num) break;
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buf[count++] = SOC_ADC_RNDH;
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}
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return count;
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}
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void random_poweron(void)
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{
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}
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void random_poweroff(void)
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{
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}
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#endif /* RANDOM_NUMOF */
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