i am aware of baudrate and i set it right.
#include <stm32f4xx.h>
#include <misc.h> // I recommend you have a look at these in the ST firmware folder
#include <stm32f4xx_usart.h> // under Libraries/STM32F4xx_StdPeriph_Driver/inc and src
#define MAX_STRLEN 12 // this is the maximum string length of our string in characters
volatile char received_string[MAX_STRLEN+1]; // this will hold the recieved string
void Delay(__IO uint32_t nCount) {
while(nCount--) {
}
}
/* This funcion initializes the USART1 peripheral
*
* Arguments: baudrate --> the baudrate at which the USART is
* supposed to operate
*/
void init_USART1(uint32_t baudrate){
/* This is a concept that has to do with the libraries provided by ST
* to make development easier the have made up something similar to
* classes, called TypeDefs, which actually just define the common
* parameters that every peripheral needs to work correctly
*
* They make our life easier because we don't have to mess around with
* the low level stuff of setting bits in the correct registers
*/
GPIO_InitTypeDef GPIO_InitStruct; // this is for the GPIO pins used as TX and RX
USART_InitTypeDef USART_InitStruct; // this is for the USART1 initilization
/* enable APB2 peripheral clock for USART1
* note that only USART1 and USART6 are connected to APB2
* the other USARTs are connected to APB1
*/
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
/* enable the peripheral clock for the pins used by
* USART1, PB6 for TX and PB7 for RX
*/
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);
/* This sequence sets up the TX and RX pins
* so they work correctly with the USART1 peripheral
*/
GPIO_InitStruct.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7; // Pins 6 (TX) and 7 (RX) are used
GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF; // the pins are configured as alternate function so the USART peripheral has access to them
GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz; // this defines the IO speed and has nothing to do with the baudrate!
GPIO_InitStruct.GPIO_OType = GPIO_OType_PP; // this defines the output type as push pull mode (as opposed to open drain)
GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_UP; // this activates the pullup resistors on the IO pins
GPIO_Init(GPIOB, &GPIO_InitStruct); // now all the values are passed to the GPIO_Init() function which sets the GPIO registers
/* The RX and TX pins are now connected to their AF
* so that the USART1 can take over control of the
* pins
*/
GPIO_PinAFConfig(GPIOB, GPIO_PinSource6, GPIO_AF_USART1);
GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_USART1);
/* Now the USART_InitStruct is used to define the
* properties of USART1
*/
USART_InitStruct.USART_BaudRate = baudrate; // the baudrate is set to the value we passed into this init function
USART_InitStruct.USART_WordLength = USART_WordLength_8b;// we want the data frame size to be 8 bits (standard)
USART_InitStruct.USART_StopBits = USART_StopBits_1; // we want 1 stop bit (standard)
USART_InitStruct.USART_Parity = USART_Parity_No; // we don't want a parity bit (standard)
USART_InitStruct.USART_HardwareFlowControl = USART_HardwareFlowControl_None; // we don't want flow control (standard)
USART_InitStruct.USART_Mode = USART_Mode_Tx | USART_Mode_Rx; // we want to enable the transmitter and the receiver
USART_Init(USART1, &USART_InitStruct); // again all the properties are passed to the USART_Init function which takes care of all the bit setting
/* Here the USART1 receive interrupt is enabled
* and the interrupt controller is configured
* to jump to the USART1_IRQHandler() function
* if the USART1 receive interrupt occurs
*/
USART_ITConfig(USART1, USART_IT_RXNE, ENABLE); // enable the USART1 receive interrupt
// finally this enables the complete USART1 peripheral
USART_Cmd(USART1, ENABLE);
}
/* This function is used to transmit a string of characters via
* the USART specified in USARTx.
*
* It takes two arguments: USARTx --> can be any of the USARTs e.g. USART1, USART2 etc.
* (volatile) char *s is the string you want to send
*
* Note: The string has to be passed to the function as a pointer because
* the compiler doesn't know the 'string' data type. In standard
* C a string is just an array of characters
*
* Note 2: At the moment it takes a volatile char because the received_string variable
* declared as volatile char --> otherwise the compiler will spit out warnings
* */
void USART_puts(USART_TypeDef* USARTx, volatile char *s){
while(*s){
// wait until data register is empty
while( !(USARTx->SR & 0x00000040) );
USART_SendData(USARTx, *s);
*s++;
}
}
int main(void) {
init_USART1(9600); // initialize USART1 @ 9600 baud
USART_puts(USART1, "hello world"); // just send a message to indicate that it works
while (1)
{
}
}
comments are not mine, they are author's who posted this on internet
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