micropython/ports/bare-arm/system.c

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