Amend step 6

README.md

@@ -1410,7 +1410,7 @@ CubeMX can automate the process and make it easy and visual.
 enum { APB1_PRE = 5 /* AHB clock / 4 */, APB2_PRE = 4 /* AHB clock / 2 */ };
 enum { PLL_HSI = 16, PLL_M = 8, PLL_N = 180, PLL_P = 2 }; // Run at 180 Mhz
 #define PLL_FREQ (PLL_HSI * PLL_N / PLL_M / PLL_P)
-#define FREQ (PLL_FREQ * 1000000)
+#define SYS_FREQUENCY (PLL_FREQ * 1000000)
 ```
 
 Now we're ready for a simple algorithm to set up the clock for CPU and peripheral buses
@@ -1420,24 +1420,11 @@ may look like this:
 - Set flash latency
 - Decide on a clock source, and PLL, APB1 and APB2 prescalers
 - Configure RCC by setting respective values:
+- Move clock inititialization into a separate file `sysinit.c`, function
+ `SystemInit()` which is automatically called by the startup code
 
-```c
-static inline void clock_init(void) { // Set clock frequency
- SCB->CPACR |= ((3UL << 10 * 2) | (3UL << 11 * 2)); // Enable FPU
- FLASH->ACR |= FLASH_LATENCY | BIT(8) | BIT(9); // Flash latency, caches
- RCC->PLLCFGR &= ~((BIT(17) - 1)); // Clear PLL multipliers
- RCC->PLLCFGR |= (((PLL_P - 2) / 2) & 3) << 16; // Set PLL_P
- RCC->PLLCFGR |= PLL_M | (PLL_N << 6); // Set PLL_M and PLL_N
- RCC->CR |= BIT(24); // Enable PLL
- while ((RCC->CR & BIT(25)) == 0) spin(1); // Wait until done
- RCC->CFGR = (APB1_PRE << 10) | (APB2_PRE << 13); // Set prescalers
- RCC->CFGR |= 2; // Set clock source to PLL
- while ((RCC->CFGR & 12) == 0) spin(1); // Wait until done
-}
-```
 
-What is left, is to call `clock_init()` from main, then rebuild and reflash.
-And our board runs at its maximum speed, 180MHz!
+Rebuild and reflash, and our board runs at its maximum speed, 180MHz!
 A complete project source code you can find in [step-6-clock](step-6-clock)
 
 ## Web server with device dashboard

step-6-clock/Makefile

@@ -1,26 +1,34 @@
 CFLAGS ?= -W -Wall -Wextra -Werror -Wundef -Wshadow -Wdouble-promotion \
  -Wformat-truncation -fno-common -Wconversion \
- -g3 -Os -ffunction-sections -fdata-sections -I. -Iinclude \
- -mcpu=cortex-m4 -mthumb -mfloat-abi=hard -mfpu=fpv4-sp-d16 $(EXTRA_CFLAGS)
+ -g3 -Os -ffunction-sections -fdata-sections \
+ -I. -Iinclude -Icmsis_core/CMSIS/Core/Include -Icmsis_f4/Include \
+ -mcpu=cortex-m4 -mthumb -mfloat-abi=hard -mfpu=fpv4-sp-d16
 LDFLAGS ?= -Tlink.ld -nostartfiles -nostdlib --specs nano.specs -lc -lgcc -Wl,--gc-sections -Wl,-Map=$@.map
-SOURCES = main.c startup.c syscalls.c
+SOURCES = main.c syscalls.c sysinit.c
+SOURCES += cmsis_f4/Source/Templates/gcc/startup_stm32f429xx.s # ST startup file. Compiler-dependent!
 
 ifeq ($(OS),Windows_NT)
  RM = cmd /C del /Q /F
 else
- RM = rm -f
+ RM = rm -rf
 endif
 
 build: firmware.bin
 
-firmware.elf: $(SOURCES)
- arm-none-eabi-gcc $(SOURCES) $(CFLAGS) $(LDFLAGS) -o $@
+firmware.elf: cmsis_core cmsis_f4 hal.h link.ld Makefile $(SOURCES) 
+ arm-none-eabi-gcc $(SOURCES) $(CFLAGS) $(CFLAGS_EXTRA) $(LDFLAGS) -o $@
 
 firmware.bin: firmware.elf
  arm-none-eabi-objcopy -O binary $< $@
 
 flash: firmware.bin
  st-flash --reset write $< 0x8000000
 
+cmsis_core:
+ git clone --depth 1 -b 5.9.0 https://github.com/ARM-software/CMSIS_5 $@
+
+cmsis_f4:
+ git clone --depth 1 -b v2.6.8 https://github.com/STMicroelectronics/cmsis_device_f4 $@
+
 clean:
- $(RM) firmware.*
+ $(RM) firmware.* cmsis_*

step-6-clock/hal.h

@@ -1,17 +1,18 @@
 // Copyright (c) 2022 Cesanta Software Limited
 // All rights reserved
+// https://www.st.com/resource/en/reference_manual/dm00031020-stm32f405-415-stm32f407-417-stm32f427-437-and-stm32f429-439-advanced-arm-based-32-bit-mcus-stmicroelectronics.pdf
 
 #pragma once
 
-#include <inttypes.h>
+#include <stm32f429xx.h>
+
 #include <stdbool.h>
+#include <stdint.h>
 #include <stdio.h>
-#include <stdlib.h>
-#include <sys/stat.h>
-
-#include "stm32f429xx.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)
@@ -27,101 +28,128 @@ enum { PLL_HSI = 16, PLL_M = 8, PLL_N = 180, PLL_P = 2 }; // Run at 180 Mhz
 #define APB1_FREQUENCY (SYS_FREQUENCY / (BIT(APB1_PRE - 3)))
 
 static inline void spin(volatile uint32_t count) {
- while (count--) asm("nop");
-}
-
-static inline void systick_init(uint32_t ticks) {
- if ((ticks - 1) > 0xffffff) return; // Systick timer is 24 bit
- SysTick->LOAD = ticks - 1;
- SysTick->VAL = 0;
- SysTick->CTRL = BIT(0) | BIT(1) | BIT(2); // Enable systick
- RCC->APB2ENR |= BIT(14); // Enable SYSCFG
+ while (count--) (void) 0;
 }
 
-#define GPIO(bank) ((GPIO_TypeDef *) (GPIOA_BASE + 0x400U * (bank)))
 enum { GPIO_MODE_INPUT, GPIO_MODE_OUTPUT, GPIO_MODE_AF, GPIO_MODE_ANALOG };
-
-static inline void gpio_set_mode(uint16_t pin, uint8_t mode) {
- GPIO_TypeDef *gpio = GPIO(PINBANK(pin)); // GPIO bank
- int n = PINNO(pin); // Pin number
- RCC->AHB1ENR |= BIT(PINBANK(pin)); // Enable GPIO clock
- gpio->MODER &= ~(3U << (n * 2)); // Clear existing setting
- gpio->MODER |= (mode & 3U) << (n * 2); // Set new mode
+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 *) (0x40020000 + 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 void gpio_set_af(uint16_t pin, uint8_t af_num) {
- GPIO_TypeDef *gpio = GPIO(PINBANK(pin)); // GPIO bank
- int n = PINNO(pin); // Pin number
- gpio->AFR[n >> 3] &= ~(15UL << ((n & 7) * 4));
- gpio->AFR[n >> 3] |= ((uint32_t) af_num) << ((n & 7) * 4);
+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(PINBANK(pin));
- gpio->BSRR = (1U << PINNO(pin)) << (val ? 0 : 16);
+ 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->AHB1ENR |= 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);
 }
 
-#define UART1 USART1
-#define UART2 USART2
-#define UART3 USART3
+static inline void irq_exti_attach(uint16_t pin) {
+ uint8_t bank = (uint8_t) (PINBANK(pin)), n = (uint8_t) (PINNO(pin));
+ SYSCFG->EXTICR[n / 4] &= ~(15UL << ((n % 4) * 4));
+ SYSCFG->EXTICR[n / 4] |= (uint32_t) (bank << ((n % 4) * 4));
+ EXTI->IMR |= BIT(n);
+ EXTI->RTSR |= BIT(n);
+ EXTI->FTSR |= BIT(n);
+ int irqvec = n < 5 ? 6 + n : n < 10 ? 23 : 40; // IRQ vector index, 10.1.2
+ NVIC_SetPriority(irqvec, 3);
+ NVIC_EnableIRQ(irqvec);
+}
+
+#ifndef UART_DEBUG
+#define UART_DEBUG USART3
+#endif
 
-static inline void uart_init(USART_TypeDef *uart, unsigned long baud) {
+static inline bool uart_init(USART_TypeDef *uart, unsigned long baud) {
  // https://www.st.com/resource/en/datasheet/stm32f429zi.pdf
  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 == UART1) freq = APB2_FREQUENCY, RCC->APB2ENR |= BIT(4);
- if (uart == UART2) freq = APB1_FREQUENCY, RCC->APB1ENR |= BIT(17);
- if (uart == UART3) freq = APB1_FREQUENCY, RCC->APB1ENR |= BIT(18);
-
- if (uart == UART1) tx = PIN('A', 9), rx = PIN('A', 10);
- if (uart == UART2) tx = PIN('A', 2), rx = PIN('A', 3);
- if (uart == UART3) tx = PIN('D', 8), rx = PIN('D', 9);
-
- gpio_set_mode(tx, GPIO_MODE_AF);
- gpio_set_af(tx, af);
- gpio_set_mode(rx, GPIO_MODE_AF);
- gpio_set_af(rx, af);
+ if (uart == USART1) {
+ freq = APB2_FREQUENCY, RCC->APB2ENR |= BIT(4);
+ tx = PIN('A', 9), rx = PIN('A', 10);
+ } else if (uart == USART2) {
+ freq = APB1_FREQUENCY, RCC->APB1ENR |= BIT(17);
+ tx = PIN('A', 2), rx = PIN('A', 3);
+ } else if (uart == USART3) {
+ freq = APB1_FREQUENCY, RCC->APB1ENR |= BIT(18);
+ 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 this UART
  uart->BRR = freq / baud; // Set baud rate
  uart->CR1 |= BIT(13) | BIT(2) | BIT(3); // Set UE, RE, TE
+ return true;
 }
-
 static inline void uart_write_byte(USART_TypeDef *uart, uint8_t byte) {
  uart->DR = byte;
  while ((uart->SR & 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->SR & BIT(5); // If RXNE bit is set, data is ready
 }
-
 static inline uint8_t uart_read_byte(USART_TypeDef *uart) {
  return (uint8_t) (uart->DR & 255);
 }
 
-static inline bool timer_expired(uint32_t *t, uint32_t prd, uint32_t now) {
+static inline void rng_init(void) {
+ RCC->AHB2ENR |= RCC_AHB2ENR_RNGEN;
+ RNG->CR |= RNG_CR_RNGEN;
+}
+static inline uint32_t rng_read(void) {
+ while ((RNG->SR & RNG_SR_DRDY) == 0) (void) 0;
+ return RNG->DR;
+}
+
+#define UUID ((uint8_t *) UID_BASE) // Unique 96-bit chip ID. TRM 39.1
+
+// Helper macro for MAC generation
+#define GENERATE_LOCALLY_ADMINISTERED_MAC() \
+ { \
+ 2, UUID[0] ^ UUID[1], UUID[2] ^ UUID[3], UUID[4] ^ UUID[5], \
+ UUID[6] ^ UUID[7] ^ UUID[8], UUID[9] ^ UUID[10] ^ UUID[11] \
+ }
+
+static inline bool timer_expired(volatile uint32_t *t, uint32_t prd,
+ uint32_t now) {
  if (now + prd < *t) *t = 0; // Time wrapped? Reset timer
  if (*t == 0) *t = now + prd; // Firt poll? Set expiration
  if (*t > now) return false; // Not expired yet, return
  *t = (now - *t) > prd ? now + prd : *t + prd; // Next expiration time
  return true; // Expired, return true
 }
-
-static inline void clock_init(void) { // Set clock frequency
- SCB->CPACR |= ((3UL << 10 * 2) | (3UL << 11 * 2)); // Enable FPU
- FLASH->ACR |= FLASH_LATENCY | BIT(8) | BIT(9); // Flash latency, caches
- RCC->PLLCFGR &= ~((BIT(17) - 1)); // Clear PLL multipliers
- RCC->PLLCFGR |= (((PLL_P - 2) / 2) & 3) << 16; // Set PLL_P
- RCC->PLLCFGR |= PLL_M | (PLL_N << 6); // Set PLL_M and PLL_N
- RCC->CR |= BIT(24); // Enable PLL
- while ((RCC->CR & BIT(25)) == 0) spin(1); // Wait until done
- RCC->CFGR = (APB1_PRE << 10) | (APB2_PRE << 13); // Set prescalers
- RCC->CFGR |= 2; // Set clock source to PLL
- while ((RCC->CFGR & 12) == 0) spin(1); // Wait until done
-}