I am not sure about the clock use of 24 MHz, pasting the code here:
#include <stdint.h>
#include "stm32g431xx.h"
/* */
#define GPIOAEN (1U<<0) //clock enable for port A
#define UART2EN (1U<<17) // UART2 is is connected to APB1 bus and to enable clock, APB1ENR PIN 17 should be 1
#define CR1_TE (1U<<3)
#define CR1_UE (1U<<0)
#define ISR_TXFE (1U<<23)
#define SYS_FREQ 24000000
#define APB1_CLK SYS_FREQ
#define UART_BAUDRATE 115200
static void uart_set_baudrate(USART_TypeDef *USARTx, uint32_t PeriphClk, uint32_t BaudeRate);
static uint16_t compute_uart_bd(uint32_t PeriphClk, uint32_t BaudeRate);
void uart2_write(int ch);
void uart2_tx_init(void);
int main(void)
{
uart2_tx_init();
while(1)
{
uart2_write('Y');
}
}
void uart2_write(int ch)
{
/* Make sure the UART2 DR is empty */
while(!(USART2->ISR & ISR_TXFE)) {}
/* Write the data to UART2 DR */
USART2->TDR = (ch & 0xFF);
}
void uart2_tx_init(void)
{
/* ************ configure UART2 GPIO pins ********** */
/* Enable clock access to GPIOA*/
RCC->AHB2ENR |= GPIOAEN;
/* Set PA2 (Tx) to alternate function mode */
GPIOA->MODER &= ~(1U<<4);
GPIOA->MODER |= (1U<<5);
/* Set PA2 (Tx) to alternate function type to UART2_TX AF7*/
GPIOA->AFR[0] |= (1U<<8);
GPIOA->AFR[0] |= (1U<<9);
GPIOA->AFR[0] |= (1U<<10);
GPIOA->AFR[0] &= ~(1U<<11);
/* ************ configure UART2 module ********** */
/* Configure the clock access to UART2 */
RCC->APB1ENR1 = UART2EN;
/* Configure the baud rate of UART2 */
uart_set_baudrate(USART2, APB1_CLK, UART_BAUDRATE);
/* Configure the transfer direction */
USART2->CR1 = CR1_TE;
/* Enable the UART module */
USART2->CR1 |= CR1_UE;
}
static void uart_set_baudrate(USART_TypeDef *USARTx, uint32_t PeriphClk, uint32_t BaudeRate)
{
USARTx->BRR = compute_uart_bd(PeriphClk, BaudeRate);
}
static uint16_t compute_uart_bd(uint32_t PeriphClk, uint32_t BaudeRate)
{
return((PeriphClk + (BaudeRate/2U))/BaudeRate);
}
