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
