89 lines
2.3 KiB
C
89 lines
2.3 KiB
C
/*
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* This file is part of the libopencm3 project.
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*
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* This library is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this library. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <libopencm3/cm3/common.h>
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#include <libopencm3/stm32/f4/rcc.h>
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#include <libopencm3/stm32/f4/gpio.h>
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#include <libopencm3/stm32/f4/rng.h>
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static void rcc_setup(void)
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{
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rcc_clock_setup_hse_3v3(&hse_8mhz_3v3[CLOCK_3V3_120MHZ]);
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/* Enable GPIOD clock for onboard leds. */
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rcc_peripheral_enable_clock(&RCC_AHB1ENR, RCC_AHB1ENR_IOPDEN);
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/* Enable rng clock */
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rcc_peripheral_enable_clock(&RCC_AHB2ENR, RCC_AHB2ENR_RNGEN);
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}
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static void rng_setup(void)
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{
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/* Enable interupt */
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/* Set the IE bit in the RNG_CR register. */
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RNG_CR |= RNG_CR_IE;
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/* Enable the random number generation by setting the RNGEN bit in the RNG_CR
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register. This activates the analog part, the RNG_LFSR and the error detector.
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*/
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RNG_CR |= RNG_CR_EN;
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}
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static void gpio_setup(void)
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{
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/* Setup onboard led */
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gpio_mode_setup(GPIOD, GPIO_MODE_OUTPUT, GPIO_PUPD_NONE, GPIO12 | GPIO13);
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}
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/* Tried to folow the guidelines in the stm32f4 user manual.*/
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static u32 random_int(void)
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{
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static u32 last_value=0;
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static u32 new_value=0;
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u32 error_bits = 0;
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error_bits = RNG_SR_SEIS | RNG_SR_CEIS;
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while (new_value==last_value) {
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/* Check for error flags and if data is ready. */
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if ( ((RNG_SR & error_bits) == 0) && ( (RNG_SR & RNG_SR_DRDY) == 1 ) )
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new_value=RNG_DR;
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}
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last_value=new_value;
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return new_value;
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}
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int main(void)
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{
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int i,j;
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rcc_setup();
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gpio_setup();
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rng_setup();
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while(1){
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u32 rnd;
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rnd = random_int();
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for(i=0;i!=32;++i){
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if ( (rnd & (1 << i))!=0 )
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gpio_set(GPIOD, GPIO12);
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else
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gpio_clear(GPIOD, GPIO12);
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/* Delay */
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for(j=0;j!=5000000;++j)
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__asm__("nop");
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}
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}
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}
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