diff options
Diffstat (limited to 'minimal/main.c')
| -rw-r--r-- | minimal/main.c | 159 |
1 files changed, 157 insertions, 2 deletions
diff --git a/minimal/main.c b/minimal/main.c index cb3b62508..5e104e7e8 100644 --- a/minimal/main.c +++ b/minimal/main.c @@ -94,6 +94,161 @@ void MP_WEAK __assert_func(const char *file, int line, const char *func, const c } #endif -#if !MICROPY_MIN_USE_STDOUT -void _start(void) {main(0, NULL);} +#if MICROPY_MIN_USE_CORTEX_CPU + +// this is a minimal IRQ and reset framework for any Cortex-M CPU + +extern uint32_t _estack, _sidata, _sdata, _edata, _sbss, _ebss; + +void Reset_Handler(void) __attribute__((naked)); +void Reset_Handler(void) { + // set stack pointer + asm volatile ("ldr sp, =_estack"); + // copy .data section from flash to RAM + for (uint32_t *src = &_sidata, *dest = &_sdata; dest < &_edata;) { + *dest++ = *src++; + } + // zero out .bss section + for (uint32_t *dest = &_sbss; dest < &_ebss;) { + *dest++ = 0; + } + // jump to board initialisation + void _start(void); + _start(); +} + +void Default_Handler(void) { + for (;;) { + } +} + +uint32_t isr_vector[] __attribute__((section(".isr_vector"))) = { + (uint32_t)&_estack, + (uint32_t)&Reset_Handler, + (uint32_t)&Default_Handler, // NMI_Handler + (uint32_t)&Default_Handler, // HardFault_Handler + (uint32_t)&Default_Handler, // MemManage_Handler + (uint32_t)&Default_Handler, // BusFault_Handler + (uint32_t)&Default_Handler, // UsageFault_Handler + 0, + 0, + 0, + 0, + (uint32_t)&Default_Handler, // SVC_Handler + (uint32_t)&Default_Handler, // DebugMon_Handler + 0, + (uint32_t)&Default_Handler, // PendSV_Handler + (uint32_t)&Default_Handler, // SysTick_Handler +}; + +void _start(void) { + // when we get here: stack is initialised, bss is clear, data is copied + + // 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 + #if MICROPY_MIN_USE_STM32_MCU + void stm32_init(void); + stm32_init(); + #endif + + // now that we have a basic system up and running we can call main + main(0, NULL); + + // we must not return + for (;;) { + } +} + +#endif + +#if MICROPY_MIN_USE_STM32_MCU + +// this is minimal set-up code for an STM32 MCU + +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; + +#define USART1 ((periph_uart_t*) 0x40011000) +#define GPIOA ((periph_gpio_t*) 0x40020000) +#define GPIOB ((periph_gpio_t*) 0x40020400) +#define RCC ((periph_rcc_t*) 0x40023800) + +// simple GPIO interface +#define GPIO_MODE_IN (0) +#define GPIO_MODE_OUT (1) +#define GPIO_MODE_ALT (2) +#define GPIO_PULL_NONE (0) +#define GPIO_PULL_UP (0) +#define GPIO_PULL_DOWN (1) +void gpio_init(periph_gpio_t *gpio, int pin, int mode, int pull, int alt) { + gpio->MODER = (gpio->MODER & ~(3 << (2 * pin))) | (mode << (2 * pin)); + // OTYPER is left as default push-pull + // OSPEEDR is left as default low speed + gpio->PUPDR = (gpio->PUPDR & ~(3 << (2 * pin))) | (pull << (2 * pin)); + gpio->AFR[pin >> 3] = (gpio->AFR[pin >> 3] & ~(15 << (4 * (pin & 7)))) | (alt << (4 * (pin & 7))); +} +#define gpio_get(gpio, pin) ((gpio->IDR >> (pin)) & 1) +#define gpio_set(gpio, pin, value) do { gpio->ODR = (gpio->ODR & ~(1 << (pin))) | (value << pin); } while (0) +#define gpio_low(gpio, pin) do { gpio->BSRRH = (1 << (pin)); } while (0) +#define gpio_high(gpio, pin) do { gpio->BSRRL = (1 << (pin)); } while (0) + +void stm32_init(void) { + // basic MCU config + RCC->CR |= (uint32_t)0x00000001; // set HSION + RCC->CFGR = 0x00000000; // reset all + RCC->CR &= (uint32_t)0xfef6ffff; // reset HSEON, CSSON, PLLON + RCC->PLLCFGR = 0x24003010; // reset PLLCFGR + RCC->CR &= (uint32_t)0xfffbffff; // reset HSEBYP + RCC->CIR = 0x00000000; // disable IRQs + + // leave the clock as-is (internal 16MHz) + + // enable GPIO clocks + RCC->AHB1ENR |= 0x00000003; // GPIOAEN, GPIOBEN + + // turn on an LED! (on pyboard it's the red one) + gpio_init(GPIOA, 13, GPIO_MODE_OUT, GPIO_PULL_NONE, 0); + gpio_high(GPIOA, 13); + + // enable UART1 at 9600 baud (TX=B6, RX=B7) + gpio_init(GPIOB, 6, GPIO_MODE_ALT, GPIO_PULL_NONE, 7); + gpio_init(GPIOB, 7, GPIO_MODE_ALT, GPIO_PULL_NONE, 7); + RCC->APB2ENR |= 0x00000010; // USART1EN + USART1->BRR = (104 << 4) | 3; // 16MHz/(16*104.1875) = 9598 baud + USART1->CR1 = 0x0000200c; // USART enable, tx enable, rx enable +} + #endif |