Problem with UART and STM32F413ZH

[JLask.1]

Hello,

i have a problem and hope that someone can help me. I've been trying to find a solution for days now and I'm just not able to get any further.

I would like to set up a UART interface using register. Unfortunately nothing gets to the PC.

What I have tried so far:

UART2 Tx via PA2 and PD5 . Both unsuccessful.

Additionally I tried it over a FTDI USB. This also does not work

The registers look good, as far as I can see

I tried several terminals but no success

Here is my code:

#include "stdint.h"
#include "uart.h"
#include "stm32f413xx.h"
 
#define GPIOAEN				(1U<<0)
#define UART2EN				(1U<<17)
 
#define DBG_UART_BAUDRATE	9600
#define SYS_FREQ			16000000
#define APB1_CLK			SYS_FREQ
#define CR1_TE				(1U<<3)
#define CR1_UE				(1U<<13)
#define SR_TXE				(1U<<7)
 
static void uart_set_baudrate(uint32_t periph_clk, uint32_t baudrate);
static void uart_write(int ch);
 
int __io_putchar(int ch) {
	uart_write(ch);
	return ch;
}
 
void debug_uart_init(void){
 
	/* Enable clock acces to GPIOA */
	RCC->AHB1ENR |= GPIOAEN;
 
	/* Set the mode of PA2 to alternate function mode */
	GPIOA->MODER &= ~(1U << 4);
	GPIOA->MODER |= (1U << 5);
 
	/* Set alternate function type to AF7 (UART2_TX) */
	GPIOA->AFR[0] |= (1U << 8);
	GPIOA->AFR[0] |= (1U << 9);
	GPIOA->AFR[0] |= (1U << 10);
	GPIOA->AFR[0] &= ~(1U << 11);
 
	/* Enable clock access to UART2 */
	RCC->APB1ENR |= UART2EN;
 
	/* Configure UART baudrate */
	uart_set_baudrate(APB1_CLK, DBG_UART_BAUDRATE);
 
	/* Configure transfer direction */
	USART2->CR1 = CR1_TE;
 
	/* Enable UART Module */
	USART2->CR1 = CR1_UE;
}
 
static void uart_write(int ch){
 
	/* Make sure transmit data register is empty */
	while(!(USART2->SR & SR_TXE)){}
 
	/* Write to transmit data register */
	USART2->DR = (ch & 0xFF);
}
 
 
static uint16_t compute_uart_bd(uint32_t periph_clk, uint32_t baudrate){
	return ((periph_clk + (baudrate / 2U)) / baudrate);
}
 
static void uart_set_baudrate(uint32_t periph_clk, uint32_t baudrate){
	USART2->BRR = compute_uart_bd(periph_clk, baudrate);
}

The main.c has the following code

#include "stdio.h"
#include "stm32f413xx.h"
#include "fpu.h"
#include "uart.h"
  
int main()
{
 
	/* Enable FPU */
	fpu_enable();
 
	/* Initialize debug UART */
	debug_uart_init();
 
	while(1)
	{
		printf("Hello");
		for (int i = 0; i < 9000; ++i){}
	}
}

I would be really grateful if someone could help me find the problem

[Tesla DeLorean]

Isn't HSI 16 MHz ??

Perhaps get a scope look at signals on pins.

[JLask.1]

Yes you are right HSI is 16MHz. i had also tried 16MHz and also just tried again now. unfortunately the same problem. I have also tried several terminals. MobaXterm, CoolTerm, RealTerm and Putty. 

[Tesla DeLorean]

Probably not an issue with the terminal applications, look at the signal itself, with a scope, perhaps output a continuous 'U' 0x55 pattern?

Review the register settings, per manual.

Try with a HAL example to sanity check the hardware is working as expected.

[Chris21]

It's odd that you have RCC->APB1ENR |= UART2EN; should be USART2EN.

USART2->CR1 = CR1_TE; // enable transmitter

/* Enable UART Module */

USART2->CR1 = CR1_UE; // disables transmitter

Probably want to be using |= ...

[Piranha]

#include "stm32f413xx.h"
 
#define GPIOAEN				(1U<<0)
#define UART2EN				(1U<<17)
 
#define CR1_TE				(1U<<3)
#define CR1_UE				(1U<<13)
#define SR_TXE				(1U<<7)

32-bit platform needs an "ul/UL" suffix. But why are you redefining bit field definitions instead of using ST defined ones?

[Tesla DeLorean]

Because it's more efficient, and less error prone, like repeatedly accessing the same register..

[S.Ma]

As long as short defined names aren't unfortunately reused by other peripherals using the same implementation... or these defines are "local" to a C source file....

[Tesla DeLorean]

One of the tricks with register level code is to let the COMPILER do a lot of heavy lifting ONCE at compile time, on a machine running at 3 GHz.

The compiler can fold up the math, it can't fold RMW action on VOLATILE memory, where it instead has to assure in-order-execution.