Подозрения падают на настройку baud rate, но вроде всё как в мануалах.

Полный код:#include "stm32f4xx.h"

#include "stm32f4xx_hal_gpio.h"

#include "stm32f4xx_hal_rcc.h"

#include "stm32f4xx_hal_cortex.h"

#include "stdint.h"

#include "math.h"

//define Internal RC frequencies

#define XTAL 16000000UL

//define busses prescalers

#define AHB_PRE 1

#define APB1_PRE 2

#define APB2_PRE 1

#define SysTicksClk 10000

//calculate peripheral frequencies

#define SYSCLK 84000000

#define AHB SYSCLK/AHB_PRE

#define APB1 AHB/APB1_PRE

#define APB1_TIM APB1*2

#define APB2 AHB/APB2_PRE

#define APB2_TIM APB2*1

#define SysTicks AHB/SysTicksClk

#define USART_BAUDRATE 19200

#define BUF_LEN 1

struct Data

{

char Msg[BUF_LEN];

} Message;

void USART2_IRQHandler(void)

{

if (!(USART2->SR & USART_SR_TXE))

{

if (Message.Msg[0] == (char)0x00)

GPIOA->ODR |= 1 << 1;

if (Message.Msg[0] == (char)0x01)

GPIOA->ODR |= 0 << 1;

}

if (USART2->SR & USART_SR_RXNE)

{

Message.Msg[0] = USART2->DR;

}}

int main()

{

RCC->AHB1ENR |= RCC_AHB1ENR_GPIOAEN |

RCC_AHB1ENR_GPIOBEN;

GPIOA->MODER |= 1 << 1*2; //Set GPIOA pins output mode

GPIOB->MODER |= 0 << 0*2;

GPIOA->MODER |= 0xA0;

GPIOA->AFR[0] |= 0x7700;

RCC->APB1ENR |= RCC_APB1ENR_USART2EN;

USART2->CR1 |= USART_CR1_UE; //usart enable

USART2->CR1 |= USART_CR1_TE; //transmitter enable

USART2->CR1 |= USART_CR1_RE; //receiver enable

float div = (float)APB1 /(16*(float)USART_BAUDRATE);

int integer = APB1 / (16*USART_BAUDRATE);

float flo = (div - (float)integer)*16;

int floatt = round(flo);

USART2->BRR = (( integer << 4 ) + floatt);

NVIC_EnableIRQ(USART2_IRQn);

USART2->CR1 |= USART_CR1_TXEIE;

USART2->CR1 |= USART_CR1_RXNEIE;

int i;

while(1)

{

if (!(GPIOB->IDR & GPIO_IDR_ID0))

{

i = 1;

}

else

{

if(i == 1)

{

USART2->DR &= Message.Msg[0];

while(!(USART2->SR & USART_SR_TC));

i = 0;

}}}}

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