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Add FreeRTOS example on H5

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This commit is contained in:
Sergio R. Caprile 2023-08-25 16:12:18 -03:00
parent 995a63dc39
commit be58bfe22b
14 changed files with 527 additions and 0 deletions
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examples/stm32/nucleo-h563zi-make-freertos-builtin/FreeRTOSConfig.h Normal file
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#pragma once
#include "hal.h"
#define configUSE_PREEMPTION 1
#define configCPU_CLOCK_HZ CPU_FREQUENCY
#define configTICK_RATE_HZ 1000
#define configMAX_PRIORITIES 5
#define configUSE_16_BIT_TICKS 0
#define configUSE_TICK_HOOK 0
#define configUSE_IDLE_HOOK 0
#define configUSE_TIMERS 0
#define configUSE_CO_ROUTINES 0
#define configUSE_MALLOC_FAILED_HOOK 0
#define configMINIMAL_STACK_SIZE 128
#define configTOTAL_HEAP_SIZE (1024 * 128)
#define INCLUDE_vTaskDelay 1
#define INCLUDE_xTaskGetSchedulerState 1 // trying
#ifdef __NVIC_PRIO_BITS
#define configPRIO_BITS __NVIC_PRIO_BITS
#else
#define configPRIO_BITS 4
#endif
#define configLIBRARY_LOWEST_INTERRUPT_PRIORITY 15
#define configLIBRARY_MAX_SYSCALL_INTERRUPT_PRIORITY 5
#define configKERNEL_INTERRUPT_PRIORITY \
(configLIBRARY_LOWEST_INTERRUPT_PRIORITY << (8 - configPRIO_BITS))
#define configMAX_SYSCALL_INTERRUPT_PRIORITY \
(configLIBRARY_MAX_SYSCALL_INTERRUPT_PRIORITY << (8 - configPRIO_BITS))
#define configASSERT(expr) \
if (!(expr)) printf("FAILURE %s:%d: %s\n", __FILE__, __LINE__, #expr)
// https://www.freertos.org/2020/04/using-freertos-on-armv8-m-microcontrollers.html
#define configENABLE_FPU 1
#define configENABLE_MPU 0
#define configENABLE_TRUSTZONE 0
#define configRUN_FREERTOS_SECURE_ONLY 0
//#define vPortSVCHandler SVC_Handler
//#define xPortPendSVHandler PendSV_Handler
//#define xPortSysTickHandler SysTick_Handler

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examples/stm32/nucleo-h563zi-make-freertos-builtin/Makefile Normal file
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CFLAGS = -W -Wall -Wextra -Werror -Wundef -Wshadow -Wdouble-promotion
CFLAGS += -Wformat-truncation -fno-common -Wconversion -Wno-sign-conversion
CFLAGS += -g3 -Os -ffunction-sections -fdata-sections
CFLAGS += -I. -Icmsis_core/CMSIS/Core/Include -Icmsis_h5/Include
CFLAGS += -mcpu=cortex-m33 -mthumb -mfpu=fpv5-sp-d16 -mfloat-abi=hard
LDFLAGS ?= -Tlink.ld -nostdlib -nostartfiles --specs nano.specs -lc -lgcc -Wl,--gc-sections -Wl,-Map=$@.map
SOURCES = main.c syscalls.c sysinit.c
SOURCES += cmsis_h5/Source/Templates/gcc/startup_stm32h563xx.s # ST startup file. Compiler-dependent!
# FreeRTOS. H5 has a Cortex-M33 (ARMv8) core, the CM4F port can be used if TrustZone and the MPU are not to be used, see H7 example
SOURCES += FreeRTOS-Kernel/portable/MemMang/heap_4.c
SOURCES += FreeRTOS-Kernel/portable/GCC/ARM_CM33_NTZ/non_secure/port.c
SOURCES += FreeRTOS-Kernel/portable/GCC/ARM_CM33_NTZ/non_secure/portasm.c
CFLAGS += -IFreeRTOS-Kernel/include
CFLAGS += -IFreeRTOS-Kernel/portable/GCC/ARM_CM33_NTZ/non_secure -Wno-conversion -Wno-unused-parameter
SOURCES += mongoose.c net.c packed_fs.c
CFLAGS += $(CFLAGS_EXTRA) # Mongoose options are defined in mongoose_custom.h
# Example specific build options. See README.md
CFLAGS += -DHTTP_URL=\"http://0.0.0.0/\"
ifeq ($(OS),Windows_NT)
RM = cmd /C del /Q /F /S
else
RM = rm -rf
endif
all build example: firmware.bin
firmware.bin: firmware.elf
arm-none-eabi-objcopy -O binary $< $@
firmware.elf: FreeRTOS-Kernel cmsis_core cmsis_h5 $(SOURCES) hal.h link.ld mongoose_custom.h FreeRTOSConfig.h Makefile
arm-none-eabi-gcc $(SOURCES) $(wildcard FreeRTOS-Kernel/*.c) $(CFLAGS) $(LDFLAGS) -o $@
flash: firmware.bin
st-flash --debug --freq=200 --reset write $< 0x8000000
cmsis_core: # ARM CMSIS core headers
git clone --depth 1 -b 5.9.0 https://github.com/ARM-software/CMSIS_5 $@
cmsis_h5: # ST CMSIS headers for STM32H5 series
git clone --depth 1 -b main https://github.com/STMicroelectronics/cmsis_device_h5 $@
FreeRTOS-Kernel: # FreeRTOS sources
git clone --depth 1 -b V10.5.0 https://github.com/FreeRTOS/FreeRTOS-Kernel $@
# Automated remote test. Requires env variable VCON_API_KEY set. See https://vcon.io/automated-firmware-tests/
DEVICE_URL ?= https://dash.vcon.io/api/v3/devices/11
update: firmware.bin
curl --fail-with-body -su :$(VCON_API_KEY) $(DEVICE_URL)/ota --data-binary @$<
test update: CFLAGS += -DUART_DEBUG=USART1
test: update
curl --fail-with-body -su :$(VCON_API_KEY) $(DEVICE_URL)/tx?t=5 | tee /tmp/output.txt
grep 'READY, IP:' /tmp/output.txt # Check for network init
clean:
$(RM) firmware.* *.su cmsis_core cmsis_h5 FreeRTOS-Kernel

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examples/stm32/nucleo-h563zi-make-freertos-builtin/README.md Normal file
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# FreeRTOS web device dashboard on NUCLEO-H563ZI
See https://mongoose.ws/tutorials/stm32/all-make-freertos-builtin/

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examples/stm32/nucleo-h563zi-make-freertos-builtin/hal.h Normal file
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// Copyright (c) 2022-2023 Cesanta Software Limited
// All rights reserved
//
// Datasheet: RM0481, devboard manual: UM3115
// https://www.st.com/resource/en/reference_manual/rm0481-stm32h563h573-and-stm32h562-armbased-32bit-mcus-stmicroelectronics.pdf
// Alternate functions: https://www.st.com/resource/en/datasheet/stm32h563vi.pdf
#pragma once
#include <stm32h563xx.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define BIT(x) (1UL << (x))
#define SETBITS(R, CLEARMASK, SETMASK) (R) = ((R) & ~(CLEARMASK)) | (SETMASK)
#define PIN(bank, num) ((((bank) - 'A') << 8) | (num))
#define PINNO(pin) (pin & 255)
#define PINBANK(pin) (pin >> 8)
#define LED1 PIN('B', 0) // On-board LED pin (green)
#define LED2 PIN('F', 4) // On-board LED pin (yellow)
#define LED3 PIN('G', 4) // On-board LED pin (red)
#define LED LED2 // Use yellow LED for blinking
// System clock (11.4, Figure 48; 11.4.5, Figure 51; 11.4.8
// CPU_FREQUENCY <= 250 MHz; (SYS_FREQUENCY / HPRE) ; hclk = CPU_FREQUENCY
// APB clocks <= 250 MHz. Configure flash latency (WS) in accordance to hclk
// freq (7.3.4, Table 37)
enum {
HPRE = 7, // register value, divisor value = BIT(value - 7) = / 1
PPRE1 = 4, // register values, divisor value = BIT(value - 3) = / 2
PPRE2 = 4,
PPRE3 = 4,
};
// Make sure your chip package uses the internal LDO, otherwise set PLL1_N = 200
enum { PLL1_HSI = 64, PLL1_M = 32, PLL1_N = 250, PLL1_P = 2 };
#define FLASH_LATENCY 0x25 // WRHIGHFREQ LATENCY
#define CPU_FREQUENCY ((PLL1_HSI * PLL1_N / PLL1_M / PLL1_P / (BIT(HPRE - 7))) * 1000000)
#define AHB_FREQUENCY CPU_FREQUENCY
#define APB2_FREQUENCY (AHB_FREQUENCY / (BIT(PPRE2 - 3)))
#define APB1_FREQUENCY (AHB_FREQUENCY / (BIT(PPRE1 - 3)))
static inline void spin(volatile uint32_t n) {
while (n--) (void) 0;
}
enum { GPIO_MODE_INPUT, GPIO_MODE_OUTPUT, GPIO_MODE_AF, GPIO_MODE_ANALOG };
enum { GPIO_OTYPE_PUSH_PULL, GPIO_OTYPE_OPEN_DRAIN };
enum { GPIO_SPEED_LOW, GPIO_SPEED_MEDIUM, GPIO_SPEED_HIGH, GPIO_SPEED_INSANE };
enum { GPIO_PULL_NONE, GPIO_PULL_UP, GPIO_PULL_DOWN };
#define GPIO(N) ((GPIO_TypeDef *) ((GPIOA_BASE_NS) + 0x400 * (N)))
static GPIO_TypeDef *gpio_bank(uint16_t pin) {
return GPIO(PINBANK(pin));
}
static inline void gpio_toggle(uint16_t pin) {
GPIO_TypeDef *gpio = gpio_bank(pin);
uint32_t mask = BIT(PINNO(pin));
gpio->BSRR = mask << (gpio->ODR & mask ? 16 : 0);
}
static inline int gpio_read(uint16_t pin) {
return gpio_bank(pin)->IDR & BIT(PINNO(pin)) ? 1 : 0;
}
static inline void gpio_write(uint16_t pin, bool val) {
GPIO_TypeDef *gpio = gpio_bank(pin);
gpio->BSRR = BIT(PINNO(pin)) << (val ? 0 : 16);
}
static inline void gpio_init(uint16_t pin, uint8_t mode, uint8_t type,
uint8_t speed, uint8_t pull, uint8_t af) {
GPIO_TypeDef *gpio = gpio_bank(pin);
uint8_t n = (uint8_t) (PINNO(pin));
RCC->AHB2ENR |= BIT(PINBANK(pin)); // Enable GPIO clock
SETBITS(gpio->OTYPER, 1UL << n, ((uint32_t) type) << n);
SETBITS(gpio->OSPEEDR, 3UL << (n * 2), ((uint32_t) speed) << (n * 2));
SETBITS(gpio->PUPDR, 3UL << (n * 2), ((uint32_t) pull) << (n * 2));
SETBITS(gpio->AFR[n >> 3], 15UL << ((n & 7) * 4),
((uint32_t) af) << ((n & 7) * 4));
SETBITS(gpio->MODER, 3UL << (n * 2), ((uint32_t) mode) << (n * 2));
}
static inline void gpio_input(uint16_t pin) {
gpio_init(pin, GPIO_MODE_INPUT, GPIO_OTYPE_PUSH_PULL, GPIO_SPEED_HIGH,
GPIO_PULL_NONE, 0);
}
static inline void gpio_output(uint16_t pin) {
gpio_init(pin, GPIO_MODE_OUTPUT, GPIO_OTYPE_PUSH_PULL, GPIO_SPEED_HIGH,
GPIO_PULL_NONE, 0);
}
#ifndef UART_DEBUG
#define UART_DEBUG USART3
#endif
static inline bool uart_init(USART_TypeDef *uart, unsigned long baud) {
uint8_t af = 7; // Alternate function
uint16_t rx = 0, tx = 0; // pins
uint32_t freq = 0; // Bus frequency. UART1 is on APB2, rest on APB1
if (uart == USART1) {
freq = APB2_FREQUENCY, RCC->APB2ENR |= RCC_APB2ENR_USART1EN;
tx = PIN('A', 9), rx = PIN('A', 10);
} else if (uart == USART2) {
freq = APB1_FREQUENCY, RCC->APB1LENR |= RCC_APB1LENR_USART2EN;
tx = PIN('A', 2), rx = PIN('A', 3);
} else if (uart == USART3) {
freq = APB1_FREQUENCY, RCC->APB1LENR |= RCC_APB1LENR_USART3EN;
tx = PIN('D', 8), rx = PIN('D', 9);
} else {
return false;
}
gpio_init(tx, GPIO_MODE_AF, GPIO_OTYPE_PUSH_PULL, GPIO_SPEED_HIGH, 0, af);
gpio_init(rx, GPIO_MODE_AF, GPIO_OTYPE_PUSH_PULL, GPIO_SPEED_HIGH, 0, af);
uart->CR1 = 0; // Disable UART
uart->BRR = freq / baud; // Set baud rate
uart->CR1 = USART_CR1_RE | USART_CR1_TE; // Set mode to TX & RX
uart->CR1 |= USART_CR1_UE; // Enable UART
return true;
}
static inline void uart_write_byte(USART_TypeDef *uart, uint8_t byte) {
uart->TDR = byte;
while ((uart->ISR & BIT(7)) == 0) spin(1);
}
static inline void uart_write_buf(USART_TypeDef *uart, char *buf, size_t len) {
while (len-- > 0) uart_write_byte(uart, *(uint8_t *) buf++);
}
static inline int uart_read_ready(USART_TypeDef *uart) {
return uart->ISR & BIT(5); // If RXNE bit is set, data is ready
}
static inline uint8_t uart_read_byte(USART_TypeDef *uart) {
return (uint8_t) (uart->RDR & 255);
}
static inline void rng_init(void) {
RCC->CCIPR5 |= RCC_CCIPR5_RNGSEL_0; // RNG clock source pll1_q_ck
RCC->AHB2ENR |= RCC_AHB2ENR_RNGEN; // Enable RNG clock
RNG->CR |= RNG_CR_RNGEN; // Enable RNG
}
static inline uint32_t rng_read(void) {
while ((RNG->SR & RNG_SR_DRDY) == 0) spin(1);
return RNG->DR;
}
static inline bool ldo_is_on(void) {
return (PWR->SCCR & PWR_SCCR_LDOEN) == PWR_SCCR_LDOEN;
}
static inline void ethernet_init(void) {
// Initialise Ethernet. Enable MAC GPIO pins, see UM3115 section 10.7
uint16_t pins[] = {PIN('A', 1), PIN('A', 2), PIN('A', 7),
PIN('B', 15), PIN('C', 1), PIN('C', 4),
PIN('C', 5), PIN('G', 11), PIN('G', 13)};
for (size_t i = 0; i < sizeof(pins) / sizeof(pins[0]); i++) {
gpio_init(pins[i], GPIO_MODE_AF, GPIO_OTYPE_PUSH_PULL, GPIO_SPEED_INSANE,
GPIO_PULL_NONE, 11); // 11 is the Ethernet function
}
NVIC_EnableIRQ(ETH_IRQn); // Setup Ethernet IRQ handler
RCC->APB3ENR |= RCC_APB3ENR_SBSEN; // Enable SBS clock
SETBITS(SBS->PMCR, SBS_PMCR_ETH_SEL_PHY, SBS_PMCR_ETH_SEL_PHY_2); // RMII
RCC->AHB1ENR |= RCC_AHB1ENR_ETHEN | RCC_AHB1ENR_ETHRXEN | RCC_AHB1ENR_ETHTXEN;
}
#define UUID ((uint32_t *) UID_BASE) // Unique 96-bit chip ID. TRM 59.1
// Helper macro for MAC generation, byte reads not allowed
#define GENERATE_LOCALLY_ADMINISTERED_MAC() \
{ \
2, UUID[0] & 255, (UUID[0] >> 10) & 255, (UUID[0] >> 19) & 255, \
UUID[1] & 255, UUID[2] & 255 \
}

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examples/stm32/nucleo-h563zi-make-freertos-builtin/link.ld Normal file
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ENTRY(Reset_Handler);
MEMORY {
flash(rx) : ORIGIN = 0x08000000, LENGTH = 2048k
sram(rwx) : ORIGIN = 0x20000000, LENGTH = 640k
}
_estack = ORIGIN(sram) + LENGTH(sram); /* stack points to end of SRAM */
SECTIONS {
.vectors : { KEEP(*(.isr_vector)) } > flash
.text : { *(.text* .text.*) } > flash
.rodata : { *(.rodata*) } > flash
.data : {
_sdata = .; /* for init_ram() */
*(.first_data)
*(.data SORT(.data.*))
_edata = .; /* for init_ram() */
} > sram AT > flash
_sidata = LOADADDR(.data);
.bss : {
_sbss = .; /* for init_ram() */
*(.bss SORT(.bss.*) COMMON)
_ebss = .; /* for init_ram() */
} > sram
. = ALIGN(8);
_end = .; /* for cmsis_gcc.h and init_ram() */
}

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examples/stm32/nucleo-h563zi-make-freertos-builtin/main.c Normal file
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// Copyright (c) 2023 Cesanta Software Limited
// All rights reserved
#include "hal.h"
#include "mongoose.h"
#include "net.h"
#define BLINK_PERIOD_MS 1000 // LED blinking period in millis
void mg_random(void *buf, size_t len) { // Use on-board RNG
for (size_t n = 0; n < len; n += sizeof(uint32_t)) {
uint32_t r = rng_read();
memcpy((char *) buf + n, &r, n + sizeof(r) > len ? len - n : sizeof(r));
}
}
static void timer_fn(void *arg) {
struct mg_tcpip_if *ifp = arg; // And show
const char *names[] = {"down", "up", "req", "ready"}; // network stats
MG_INFO(("Ethernet: %s, IP: %M, rx:%u, tx:%u, dr:%u, er:%u",
names[ifp->state], mg_print_ip4, &ifp->ip, ifp->nrecv, ifp->nsent,
ifp->ndrop, ifp->nerr));
}
static void server(void *args) {
struct mg_mgr mgr; // Initialise Mongoose event manager
mg_mgr_init(&mgr); // and attach it to the interface
mg_log_set(MG_LL_DEBUG); // Set log level
// Initialise Mongoose network stack
ethernet_init();
struct mg_tcpip_driver_stm32h_data driver_data = {.mdc_cr = 4};
struct mg_tcpip_if mif = {.mac = GENERATE_LOCALLY_ADMINISTERED_MAC(),
// Uncomment below for static configuration:
// .ip = mg_htonl(MG_U32(192, 168, 0, 223)),
// .mask = mg_htonl(MG_U32(255, 255, 255, 0)),
// .gw = mg_htonl(MG_U32(192, 168, 0, 1)),
.driver = &mg_tcpip_driver_stm32h,
.driver_data = &driver_data};
mg_tcpip_init(&mgr, &mif);
mg_timer_add(&mgr, BLINK_PERIOD_MS, MG_TIMER_REPEAT, timer_fn, &mif);
MG_INFO(("MAC: %M. Waiting for IP...", mg_print_mac, mif.mac));
while (mif.state != MG_TCPIP_STATE_READY) {
mg_mgr_poll(&mgr, 0);
}
MG_INFO(("Initialising application..."));
web_init(&mgr);
MG_INFO(("Starting event loop"));
for (;;) mg_mgr_poll(&mgr, 1); // Infinite event loop
(void) args;
}
static void blinker(void *args) {
gpio_init(LED, GPIO_MODE_OUTPUT, GPIO_OTYPE_PUSH_PULL, GPIO_SPEED_MEDIUM,
GPIO_PULL_NONE, 0);
for (;;) {
gpio_toggle(LED);
vTaskDelay(pdMS_TO_TICKS(BLINK_PERIOD_MS));
}
(void) args;
}
int main(void) {
uart_init(UART_DEBUG, 115200); // Initialise UART
// Start tasks. NOTE: stack sizes are in 32-bit words
xTaskCreate(blinker, "blinker", 128, ":)", configMAX_PRIORITIES - 1, NULL);
xTaskCreate(server, "server", 2048, 0, configMAX_PRIORITIES - 1, NULL);
vTaskStartScheduler(); // This blocks
return 0;
}

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examples/stm32/nucleo-h563zi-make-freertos-builtin/mongoose.c Symbolic link
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../../../mongoose.c

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examples/stm32/nucleo-h563zi-make-freertos-builtin/mongoose.h Symbolic link
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../../../mongoose.h

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examples/stm32/nucleo-h563zi-make-freertos-builtin/mongoose_custom.h Normal file
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#pragma once
#include <errno.h> // we are not using lwIP
// See https://mongoose.ws/documentation/#build-options
#define MG_ARCH MG_ARCH_FREERTOS
#define MG_ENABLE_TCPIP 1
#define MG_ENABLE_DRIVER_STM32H 1
#define MG_IO_SIZE 256
#define MG_ENABLE_CUSTOM_RANDOM 1
#define MG_ENABLE_PACKED_FS 1

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examples/stm32/nucleo-h563zi-make-freertos-builtin/net.c Symbolic link
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../../device-dashboard/net.c

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examples/stm32/nucleo-h563zi-make-freertos-builtin/net.h Symbolic link
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../../device-dashboard/net.h

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examples/stm32/nucleo-h563zi-make-freertos-builtin/packed_fs.c Symbolic link
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../../device-dashboard/packed_fs.c

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#include <sys/stat.h>
#include "hal.h"
int _fstat(int fd, struct stat *st) {
if (fd < 0) return -1;
st->st_mode = S_IFCHR;
return 0;
}
void *_sbrk(int incr) {
extern char _end;
static unsigned char *heap = NULL;
unsigned char *prev_heap;
if (heap == NULL) heap = (unsigned char *) &_end;
prev_heap = heap;
heap += incr;
return prev_heap;
}
int _open(const char *path) {
(void) path;
return -1;
}
int _close(int fd) {
(void) fd;
return -1;
}
int _isatty(int fd) {
(void) fd;
return 1;
}
int _lseek(int fd, int ptr, int dir) {
(void) fd, (void) ptr, (void) dir;
return 0;
}
void _exit(int status) {
(void) status;
for (;;) asm volatile("BKPT #0");
}
void _kill(int pid, int sig) {
(void) pid, (void) sig;
}
int _getpid(void) {
return -1;
}
int _write(int fd, char *ptr, int len) {
(void) fd, (void) ptr, (void) len;
if (fd == 1) uart_write_buf(UART_DEBUG, ptr, (size_t) len);
return -1;
}
int _read(int fd, char *ptr, int len) {
(void) fd, (void) ptr, (void) len;
return -1;
}
int _link(const char *a, const char *b) {
(void) a, (void) b;
return -1;
}
int _unlink(const char *a) {
(void) a;
return -1;
}
int _stat(const char *path, struct stat *st) {
(void) path, (void) st;
return -1;
}
int mkdir(const char *path, mode_t mode) {
(void) path, (void) mode;
return -1;
}
void _init(void) {}

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// Copyright (c) 2023 Cesanta Software Limited
// All rights reserved
//
// This file contains essentials required by the CMSIS:
// uint32_t SystemCoreClock - holds the system core clock value
// SystemInit() - initialises the system, e.g. sets up clocks
#include "hal.h"
uint32_t SystemCoreClock = CPU_FREQUENCY;
void SystemInit(void) { // Called automatically by startup code
SCB->CPACR |= ((3UL << 20U) | (3UL << 22U)); // Enable FPU
asm("DSB");
asm("ISB");
if (ldo_is_on()) {
PWR->VOSCR = PWR_VOSCR_VOS_0 | PWR_VOSCR_VOS_1; // Select VOS0
} else {
PWR->VOSCR = PWR_VOSCR_VOS_1; // Select VOS1
}
uint32_t f = PWR->VOSCR; // fake read to wait for bus clocking
while ((PWR->VOSSR & PWR_VOSSR_ACTVOSRDY) == 0) spin(1);
(void) f;
FLASH->ACR |= FLASH_LATENCY;
RCC->CR = RCC_CR_HSION; // Clear HSI clock divisor
while ((RCC->CR & RCC_CR_HSIRDY) == 0) spin(1); // Wait until done
RCC->CFGR2 = (PPRE3 << 12) | (PPRE2 << 8) | (PPRE1 << 4) | (HPRE << 0);
RCC->PLL1DIVR =
((PLL1_P - 1) << 9) | ((PLL1_N - 1) << 0); // Set PLL1_P PLL1_N
// Enable P and Q divider outputs; set PLL1_M, select HSI as source,
// !PLL1VCOSEL, PLL1RGE=0
RCC->PLL1CFGR =
RCC_PLL1CFGR_PLL1QEN | RCC_PLL1CFGR_PLL1PEN | (PLL1_M << 8) | (1 << 0);
RCC->CR |= RCC_CR_PLL1ON; // Enable PLL1
while ((RCC->CR & RCC_CR_PLL1RDY) == 0) spin(1); // Wait until done
RCC->CFGR1 |= (3 << 0); // Set clock source to PLL1
while ((RCC->CFGR1 & (7 << 3)) != (3 << 3)) spin(1); // Wait until done
rng_init(); // Initialise random number generator
SysTick_Config(CPU_FREQUENCY / 1000); // Sys tick every 1ms
}