| /* |
| * Copyright (c) 2020, The OpenThread Authors. |
| * 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. |
| */ |
| |
| /** |
| * @file |
| * This file implements an entropy source based on ADC. |
| * |
| */ |
| |
| #include <openthread/platform/entropy.h> |
| |
| #include "utils/code_utils.h" |
| |
| #include "em_adc.h" |
| #include "em_cmu.h" |
| |
| enum |
| { |
| EFR32_ADC_REF_CLOCK = 7000000, |
| }; |
| |
| void efr32RandomInit(void) |
| { |
| /* Enable ADC Clock */ |
| CMU_ClockEnable(cmuClock_ADC0, true); |
| ADC_Init_TypeDef init = ADC_INIT_DEFAULT; |
| ADC_InitSingle_TypeDef singleInit = ADC_INITSINGLE_DEFAULT; |
| |
| /* Initialize the ADC with the required values */ |
| init.timebase = ADC_TimebaseCalc(0); |
| init.prescale = ADC_PrescaleCalc(EFR32_ADC_REF_CLOCK, 0); |
| ADC_Init(ADC0, &init); |
| |
| /* Initialize for single conversion specific to RNG */ |
| singleInit.reference = adcRefVEntropy; |
| singleInit.diff = true; |
| singleInit.posSel = adcPosSelVSS; |
| singleInit.negSel = adcNegSelVSS; |
| ADC_InitSingle(ADC0, &singleInit); |
| |
| /* Set VINATT to maximum value and clear FIFO */ |
| ADC0->SINGLECTRLX |= _ADC_SINGLECTRLX_VINATT_MASK; |
| ADC0->SINGLEFIFOCLEAR = ADC_SINGLEFIFOCLEAR_SINGLEFIFOCLEAR; |
| } |
| |
| static uint32_t randomUint32Get(void) |
| { |
| uint8_t tmp; |
| uint32_t random = 0; |
| |
| for (int i = 0; i < 4; i++) |
| { |
| tmp = 0; |
| |
| for (int j = 0; j < 3; j++) |
| { |
| ADC_Start(ADC0, adcStartSingle); |
| |
| while ((ADC0->IF & ADC_IF_SINGLE) == 0) |
| ; |
| |
| tmp |= ((ADC_DataSingleGet(ADC0) & 0x07) << (j * 3)); |
| } |
| |
| random |= (tmp & 0xff) << (i * 8); |
| } |
| |
| return random; |
| } |
| |
| otError otPlatEntropyGet(uint8_t *aOutput, uint16_t aOutputLength) |
| { |
| otError error = OT_ERROR_NONE; |
| |
| otEXPECT_ACTION(aOutput, error = OT_ERROR_INVALID_ARGS); |
| |
| for (uint16_t length = 0; length < aOutputLength; length++) |
| { |
| aOutput[length] = (uint8_t)randomUint32Get(); |
| } |
| |
| exit: |
| return error; |
| } |