Solved
STM32F4 and USART issues
Posted on November 07, 2017 at 23:41
Hello,
I am trying to run a custom example of USART6 transmitter from the STM32F4 Discovery (so using an STM32F407VGT) and I am having problems since I only see garbage characters like '�' through the PC serial console (Putty or screen).The source code I am testing is the following one:
#include <stm32f4xx.h>
volatile uint8_t flag;
void EXTI0_IRQHandler(void)
{
//USART_SendData(USART6, 0xaa);
if(EXTI_GetITStatus(EXTI_Line0) != RESET)
{
// keep the ISR as short as possible
// set the flag and go out
USART_SendData(USART6, 0x41);
EXTI_ClearITPendingBit(EXTI_Line0);
}
}
int main(void)
{
// GPIO, NVIC and EXTI declarations
GPIO_InitTypeDef gpio_t;
USART_InitTypeDef usart_t;
//USART_ClockInitTypeDef usart_clk_t;
NVIC_InitTypeDef nvic_t;
EXTI_InitTypeDef exti_t;
RCC_DeInit();
// Enable resonator frequency
RCC_HSEConfig(RCC_HSE_ON);
while (!RCC_WaitForHSEStartUp())
;
//RCC_PLLCmd(DISABLE);
//RCC_PLLConfig(uint32_t RCC_PLLSource, uint32_t PLLM, uint32_t PLLN, uint32_t PLLP, uint32_t PLLQ)
RCC_PLLConfig(RCC_PLLSource_HSE, 4, 50, 2, 1);
RCC_PLLCmd(ENABLE);
while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) != SET)
;
// Configure AHBP Clock
RCC_HCLKConfig(RCC_SYSCLK_Div1);
// set APB2 clock divider (PPRE2 bits)
RCC_PCLK2Config(RCC_HCLK_Div2);
// Sys clock config is the PLL
RCC_SYSCLKConfig(RCC_SYSCLKSource_HSE);
//RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
SystemCoreClockUpdate();
// Enable SYSCFG and USART6 Clock
RCC_APB2PeriphClockCmd(RCC_APB2Periph_SYSCFG | RCC_APB2Periph_USART6, ENABLE);
// Enable GPIOA and GPIOC Clock
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA | RCC_AHB1Periph_GPIOC, ENABLE);
// configure GPIOA_0 as input
gpio_t.GPIO_Pin = GPIO_Pin_0;
gpio_t.GPIO_Mode = GPIO_Mode_IN;
//gpio_t.GPIO_OType = GPIO_OType_PP;
gpio_t.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_Init(GPIOA, &gpio_t);
// configure GPIOC_6 to AF USART6 Tx
// Configure port as pushpull, 50MHz and No pull up & down
//gpio_t.GPIO_OType = GPIO_OType_PP;
//gpio_t.GPIO_PuPd = GPIO_PuPd_NOPULL;
//gpio_t.GPIO_Speed = GPIO_Speed_2MHz;
// Configure PC6 as alternate function
gpio_t.GPIO_Pin = GPIO_Pin_6;
gpio_t.GPIO_Mode = GPIO_Mode_AF;
GPIO_Init(GPIOC, &gpio_t);
// Configure PC7 as alternate function
gpio_t.GPIO_Pin = GPIO_Pin_7;
gpio_t.GPIO_Mode = GPIO_Mode_AF;
GPIO_Init(GPIOC, &gpio_t);
/* Connect PC6 to USART6_Tx*/
GPIO_PinAFConfig(GPIOC, GPIO_PinSource6, GPIO_AF_USART6);
/* Connect PC7 to USART6_Rx*/
GPIO_PinAFConfig(GPIOC, GPIO_PinSource7, GPIO_AF_USART6);
usart_t.USART_BaudRate = 115200;
usart_t.USART_WordLength = USART_WordLength_8b;
usart_t.USART_StopBits = USART_StopBits_1;
//usart_t.USART_Parity = USART_Parity_No;
usart_t.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
usart_t.USART_Mode = USART_Mode_Tx | USART_Mode_Rx;
USART_Init(USART6, &usart_t);
USART_Cmd(USART6, ENABLE);
// Configure external interrupt for PA0
SYSCFG_EXTILineConfig(EXTI_PortSourceGPIOA, EXTI_PinSource0);
exti_t.EXTI_Line = EXTI_Line0;
exti_t.EXTI_Mode = EXTI_Mode_Interrupt;
exti_t.EXTI_Trigger = EXTI_Trigger_Rising;
exti_t.EXTI_LineCmd = ENABLE;
EXTI_Init(&exti_t);
// enable EXTI0 interrupt for NVIC
nvic_t.NVIC_IRQChannel = EXTI0_IRQn;
nvic_t.NVIC_IRQChannelPreemptionPriority = 0;
nvic_t.NVIC_IRQChannelSubPriority = 0;
nvic_t.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&nvic_t);
flag = 1;
while(1)
{
if(flag)
{
USART_SendData(USART6, 0x01);
}
}
return 0;
}
�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?Even if the serial console configuration matches the USART configuration, I cannot receive the correct character.
Digital logic (both Tx and Rx side) is all working at 3V3, so the voltage threshold are OK.The USART configuration is copied from the USART_HyperTerminal example of Standard Peripheral Libraries.
What's wrong or what more configuration I am missing in my code ? Thank you in advance.Regards,
Simon
