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29 * Copyright 2010 Develer S.r.l. (http://www.develer.com/)
33 * \brief LM3 backend implementation entropy pulling.
34 * \author Giovanni Bajo <rasky@develer.com>
39 #include <cpu/power.h>
41 #include <drv/clock_lm3s.h>
44 * Return the cpu core temperature in raw format
46 INLINE uint16_t hw_readRawTemp(void)
48 /* Trig the temperature sampling */
49 HWREG(ADC0_BASE + ADC_O_PSSI) |= ADC_PSSI_SS3;
51 while (!(HWREG(ADC0_BASE + ADC_O_SSFSTAT3) & ADC_SSFSTAT3_FULL))
54 return (uint16_t)HWREG(ADC0_BASE + ADC_O_SSFIFO3);
57 INLINE void hw_initIntTemp(void)
59 SYSCTL_RCGC0_R |= SYSCTL_RCGC0_ADC0;
63 /* Disable all sequence */
64 HWREG(ADC0_BASE + ADC_O_ACTSS) = 0;
65 /* Set trigger event to programmed (for all sequence) */
66 HWREG(ADC0_BASE + ADC_O_EMUX) = 0;
67 /* Enalbe read of temperature sensor */
68 HWREG(ADC0_BASE + ADC_O_SSCTL3) |= ADC_SSCTL3_TS0;
69 /* Enable sequence S03 (single sample on select channel) */
70 HWREG(ADC0_BASE + ADC_O_ACTSS) |= ADC_ACTSS_ASEN3;
74 void random_pull_entropy(uint8_t *entropy, size_t len)
76 // We use the internal temperature sensor of LM3S as a source of entropy.
77 // The last bit of the acquisition is very variable and with a decent distribution
78 // to consider it "entropic". It does not really matter because it will
79 // go through a randomness extractor anyway.
82 for (size_t j=0; j<len; j++)
85 for (int b=0; b<8; ++b)
86 if (hw_readRawTemp() & 1)