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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