STM32F4 USART issue

[ethhghg hhhrthrt]

Posted on May 22, 2017 at 01:33

Hello,

I've been trying to send data by uart from stm32f429i board to computer through usb. I learned from the datasheet that two pins - PA9 -tx and PA9-rx are connected to ST-LINK programmer so it seemed possible. I uploaded example code but im only getting weird ASCII chars (but baud rate on both computer and board are the same). Here is the example:

#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){ 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 NVIC_InitTypeDef NVIC_InitStructure; // this is used to configure the NVIC (nested vector interrupt controller)

/* 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_GPIOA, ENABLE);

/* This sequence sets up the TX and RX pins

* so they work correctly with the USART1 peripheral */ GPIO_InitStruct.GPIO_Pin = GPIO_Pin_9 | GPIO_Pin_10; // 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_100MHz; // 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_DOWN; // this activates the pullup resistors on the IO pins GPIO_Init(GPIOA, &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(GPIOA, GPIO_PinSource9, GPIO_AF_USART1); // GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, 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

NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn; // we want to configure the USART1 interrupts

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;// this sets the priority group of the USART1 interrupts NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0; // this sets the subpriority inside the group NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; // the USART1 interrupts are globally enabled NVIC_Init(&NVIC_InitStructure); // the properties are passed to the NVIC_Init function which takes care of the low level stuff

// 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(115200); // initialize USART1 @ 9600 baud

USART_puts(USART1, 'abcdefghijklmnoprstuwxyz\r\n'); // just send a message to indicate that it works

while (1){

//USART_puts(USART1, 'Init complete! Hello World!\r\n'); }}

// this is the interrupt request handler (IRQ) for ALL USART1 interrupts

void USART1_IRQHandler(void){

// check if the USART1 receive interrupt flag was set

if( USART_GetITStatus(USART1, USART_IT_RXNE) ){

static uint8_t cnt = 0; // this counter is used to determine the string length

char t = USART1->DR; // the character from the USART1 data register is saved in t

/* check if the received character is not the LF character (used to determine end of string)

* or the if the maximum string length has been been reached */ if( (t != '\n') && (cnt < MAX_STRLEN) ){ received_string[cnt] = t; cnt++; } else{ // otherwise reset the character counter and print the received string cnt = 0; USART_puts(USART1, received_string); } }}

[waclawek.jan]

Posted on May 22, 2017 at 11:10

Hi

rgrfggr.grfga

,

JW

[Tesla DeLorean]

Posted on May 22, 2017 at 13:52

Make sure PLL settings and HSE_VALUE reflect an 8 MHz clock source.