Contiki-NG
random.c
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1 /*
2  * Copyright (c) 2012, Texas Instruments Incorporated - http://www.ti.com/
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
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8  * 1. Redistributions of source code must retain the above copyright
9  * notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  * notice, this list of conditions and the following disclaimer in the
12  * documentation and/or other materials provided with the distribution.
13  *
14  * 3. Neither the name of the copyright holder nor the names of its
15  * contributors may be used to endorse or promote products derived
16  * from this software without specific prior written permission.
17  *
18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
21  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
22  * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
23  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
24  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
25  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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27  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
29  * OF THE POSSIBILITY OF SUCH DAMAGE.
30  */
31 /**
32  * \addtogroup cc2538
33  * @{
34  *
35  * \defgroup cc2538-random cc2538 Random Number Generator
36  *
37  * Driver for the cc2538 Hardware Random Number Generator
38  * @{
39  *
40  * \file
41  * Random number generator routines exploiting the cc2538 hardware
42  * capabilities.
43  *
44  * This file overrides os/lib/random.c.
45  */
46 #include "contiki.h"
47 #include "dev/rfcore.h"
48 #include "dev/cc2538-rf.h"
49 #include "dev/soc-adc.h"
50 #include "dev/sys-ctrl.h"
51 #include "reg.h"
52 /*---------------------------------------------------------------------------*/
53 /**
54  * \brief Generates a new random number using the cc2538 RNG.
55  * \return The random number.
56  */
57 unsigned short
59 {
60  uint32_t rv;
61 
62  /* Clock the RNG LSFR once */
64 
65  rv = REG(SOC_ADC_RNDL) | (REG(SOC_ADC_RNDH) << 8);
66  return ((unsigned short)rv);
67 }
68 /*---------------------------------------------------------------------------*/
69 /**
70  * \brief Seed the cc2538 random number generator.
71  * \param seed Ignored. It's here because the function prototype is in core.
72  *
73  * We form a seed for the RNG by sampling IF_ADC as
74  * discussed in the user guide.
75  * Seeding with this method should not be done during
76  * normal radio operation. Thus, use this function before
77  * initialising the network.
78  *
79  * \note Must not be called after the RF driver has been initialised and is
80  * in normal operation. If it is absolutely necessary to do so, the
81  * radio will need re-initialised.
82  */
83 void
84 random_init(unsigned short seed)
85 {
86  int i;
87  unsigned short s = 0;
88 
89  /* Make sure the RNG is on */
91 
92  /* Enable clock for the RF Core */
93  REG(SYS_CTRL_RCGCRFC) = 1;
94 
95  /* Wait for the clock ungating to take effect */
96  while(REG(SYS_CTRL_RCGCRFC) != 1);
97 
98  /* Infinite RX - FRMCTRL0[3:2] = 10
99  * This will mess with radio operation - see note above */
100  REG(RFCORE_XREG_FRMCTRL0) = 0x00000008;
101 
102  /* Turn RF on */
104 
105  /*
106  * Wait until "the chip has been in RX long enough for the transients to
107  * have died out. A convenient way to do this is to wait for the RSSI-valid
108  * signal to go high."
109  */
111 
112  /*
113  * Form the seed by concatenating bits from IF_ADC in the RF receive path.
114  * Keep sampling until we have read at least 16 bits AND the seed is valid
115  *
116  * Invalid seeds are 0x0000 and 0x8003 and should not be used.
117  */
118  while(s == 0x0000 || s == 0x8003) {
119  for(i = 0; i < 16; i++) {
121  s <<= 1;
122  }
123  }
124 
125  /* High byte first */
126  REG(SOC_ADC_RNDL) = (s >> 8) & 0x00FF;
127  REG(SOC_ADC_RNDL) = s & 0xFF;
128 
129  /* RF Off. NETSTACK_RADIO.init() will sort out normal RF operation */
131 }
132 
133 /**
134  * @}
135  * @}
136  */
Top-level header file for cc2538 RF Core registers.
#define SYS_CTRL_RCGCRFC
RF Core clocks - active mode.
Definition: sys-ctrl.h:93
Header file for the cc2538 System Control driver.
Header file for the cc2538 RF driver.
#define RFCORE_XREG_RFRND
Random data.
Definition: rfcore-xreg.h:83
Header file with register manipulation macro definitions.
Header file with register declarations for the cc2538 ADC and H/W RNG.
#define CC2538_RF_CSP_ISRXON()
Send an RX ON command strobe to the CSP.
Definition: cc2538-rf.h:95
#define CC2538_RF_CSP_ISRFOFF()
Send a RF OFF command strobe to the CSP.
Definition: cc2538-rf.h:107
#define RFCORE_XREG_RSSISTAT
RSSI valid status register.
Definition: rfcore-xreg.h:69
#define RFCORE_XREG_FRMCTRL0
Frame handling.
Definition: rfcore-xreg.h:53
#define RFCORE_XREG_RFRND_IRND
Random bit from the I channel.
Definition: rfcore-xreg.h:413
#define SOC_ADC_RNDH
RNG high byte.
Definition: soc-adc.h:55
#define SOC_ADC_ADCCON1
ADC Control 1.
Definition: soc-adc.h:49
void random_init(unsigned short seed)
Seed the cc2538 random number generator.
Definition: random.c:84
#define SOC_ADC_RNDL
RNG low byte.
Definition: soc-adc.h:54
#define SOC_ADC_ADCCON1_RCTRL0
RCTRL low bit.
Definition: soc-adc.h:67
#define RFCORE_XREG_RSSISTAT_RSSI_VALID
RSSI value is valid.
Definition: rfcore-xreg.h:327
unsigned short random_rand(void)
Generates a new random number using the cc2538 RNG.
Definition: random.c:58
#define SOC_ADC_ADCCON1_RCTRL1
RCTRL high bit.
Definition: soc-adc.h:66