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31 * This file implements an entropy source based on ADC.
35 #include <openthread/platform/entropy.h>
37 #include "utils/code_utils.h"
44 EFR32_ADC_REF_CLOCK = 7000000,
47 void efr32RandomInit(void)
49 /* Enable ADC Clock */
50 CMU_ClockEnable(cmuClock_ADC0, true);
51 ADC_Init_TypeDef init = ADC_INIT_DEFAULT;
52 ADC_InitSingle_TypeDef singleInit = ADC_INITSINGLE_DEFAULT;
54 /* Initialize the ADC with the required values */
55 init.timebase = ADC_TimebaseCalc(0);
56 init.prescale = ADC_PrescaleCalc(EFR32_ADC_REF_CLOCK, 0);
57 ADC_Init(ADC0, &init);
59 /* Initialize for single conversion specific to RNG */
60 singleInit.reference = adcRefVEntropy;
61 singleInit.diff = true;
62 singleInit.posSel = adcPosSelVSS;
63 singleInit.negSel = adcNegSelVSS;
64 ADC_InitSingle(ADC0, &singleInit);
66 /* Set VINATT to maximum value and clear FIFO */
67 ADC0->SINGLECTRLX |= _ADC_SINGLECTRLX_VINATT_MASK;
68 ADC0->SINGLEFIFOCLEAR = ADC_SINGLEFIFOCLEAR_SINGLEFIFOCLEAR;
71 static uint32_t randomUint32Get(void)
76 for (int i = 0; i < 4; i++)
80 for (int j = 0; j < 3; j++)
82 ADC_Start(ADC0, adcStartSingle);
84 while ((ADC0->IF & ADC_IF_SINGLE) == 0)
87 tmp |= ((ADC_DataSingleGet(ADC0) & 0x07) << (j * 3));
90 random |= (tmp & 0xff) << (i * 8);
96 otError otPlatEntropyGet(uint8_t *aOutput, uint16_t aOutputLength)
98 otError error = OT_ERROR_NONE;
100 otEXPECT_ACTION(aOutput, error = OT_ERROR_INVALID_ARGS);
102 for (uint16_t length = 0; length < aOutputLength; length++)
104 aOutput[length] = (uint8_t)randomUint32Get();