4fc2866f45
This commit simplifies and cleans up the bare-arm port, and adds just enough system and library code to make it execute on an STM32F405 MCU. The mpconfigport.h configuration is simplified to just specify those configuration values that are different from the defaults. And the addition of -fdata-sections and -ffunction-sections means the final firmware is smaller than it previously was, by about 4200 bytes. A README is also added. Signed-off-by: Damien George <damien@micropython.org>
143 lines
4.4 KiB
C
143 lines
4.4 KiB
C
/*
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* This file is part of the MicroPython project, http://micropython.org/
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*
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* The MIT License (MIT)
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*
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* Copyright (c) 2021 Damien P. George
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include <stdint.h>
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#include <string.h>
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#define RCC ((periph_rcc_t *)0x40023800)
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#define GPIOA ((periph_gpio_t *)0x40020000)
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#define UART4 ((periph_uart_t *)0x40004C00)
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typedef struct {
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volatile uint32_t CR;
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volatile uint32_t PLLCFGR;
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volatile uint32_t CFGR;
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volatile uint32_t CIR;
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uint32_t _1[8];
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volatile uint32_t AHB1ENR;
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volatile uint32_t AHB2ENR;
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volatile uint32_t AHB3ENR;
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uint32_t _2;
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volatile uint32_t APB1ENR;
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volatile uint32_t APB2ENR;
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} periph_rcc_t;
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typedef struct {
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volatile uint32_t MODER;
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volatile uint32_t OTYPER;
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volatile uint32_t OSPEEDR;
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volatile uint32_t PUPDR;
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volatile uint32_t IDR;
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volatile uint32_t ODR;
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volatile uint16_t BSRRL;
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volatile uint16_t BSRRH;
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volatile uint32_t LCKR;
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volatile uint32_t AFR[2];
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} periph_gpio_t;
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typedef struct {
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volatile uint32_t SR;
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volatile uint32_t DR;
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volatile uint32_t BRR;
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volatile uint32_t CR1;
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} periph_uart_t;
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extern uint32_t _estack, _sidata, _sdata, _edata, _sbss, _ebss;
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void Reset_Handler(void) __attribute__((naked));
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void bare_main(void);
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static void stm32_init(void);
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static void gpio_init_alt(periph_gpio_t *gpio, int pin, int alt);
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// Very simple ARM vector table.
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const uint32_t isr_vector[] __attribute__((section(".isr_vector"))) = {
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(uint32_t)&_estack,
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(uint32_t)&Reset_Handler,
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};
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// The CPU runs this function after a reset.
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void Reset_Handler(void) {
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// Set stack pointer.
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__asm volatile ("ldr sp, =_estack");
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// Copy .data section from flash to RAM.
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memcpy(&_sdata, &_sidata, (char *)&_edata - (char *)&_sdata);
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// Zero out .bss section.
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memset(&_sbss, 0, (char *)&_ebss - (char *)&_sbss);
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// SCB->CCR: enable 8-byte stack alignment for IRQ handlers, in accord with EABI.
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*((volatile uint32_t *)0xe000ed14) |= 1 << 9;
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// Initialise the cpu and peripherals.
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stm32_init();
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// Now that there is a basic system up and running, call the main application code.
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bare_main();
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// This function must not return.
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for (;;) {
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}
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}
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// Set up the STM32 MCU.
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static void stm32_init(void) {
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// Note: default clock is internal 16MHz.
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RCC->AHB1ENR |= 1 << 0; // GPIOAEN
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RCC->APB1ENR |= 1 << 19; // UART4EN
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gpio_init_alt(GPIOA, 0, 8);
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UART4->BRR = (8 << 4) | 11; // 16MHz/(16*8.6875) = 115107 baud
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UART4->CR1 = 0x00002008; // USART enable, tx enable, rx enable
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}
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// Configure a GPIO pin in alternate-function mode.
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static void gpio_init_alt(periph_gpio_t *gpio, int pin, int alt) {
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gpio->MODER = (gpio->MODER & ~(3 << (2 * pin))) | (2 << (2 * pin));
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// OTYPER is left as default push-pull
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// OSPEEDR is left as default low speed
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// PUPDR is left as default no-pull
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gpio->AFR[pin >> 3] = (gpio->AFR[pin >> 3] & ~(15 << (4 * (pin & 7)))) | (alt << (4 * (pin & 7)));
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}
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// Write a character out to the UART.
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static inline void uart_write_char(int c) {
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// Wait for TXE, then write the character.
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while ((UART4->SR & (1 << 7)) == 0) {
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}
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UART4->DR = c;
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}
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// Send string of given length to stdout, converting \n to \r\n.
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void mp_hal_stdout_tx_strn_cooked(const char *str, size_t len) {
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while (len--) {
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if (*str == '\n') {
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uart_write_char('\r');
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}
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uart_write_char(*str++);
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}
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}
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