使用EVT里面的GPIO_Toggle中使用下面的串口测试程序，发现printf无法将数据通过WCH-link的串口发送到上位机，但是USART3却可以。
有问题是下面这行：
printf("%c", d);
如果改成了，下面这样，又可以打印出来了，这个是什么原因呢？
printf("%c\r\n", d);
USART3可以的代码片段是：
USART_SendData(USART3, d);
复现这个问题，可以将下面的代码片段替换GPIO_Toggle的main.c：
/********************************** (C) COPYRIGHT *******************************
* File Name : main.c
* Author : WCH
* Version : V1.0.0
* Date : 2021/06/06
* Description : Main program body.
* Copyright (c) 2021 Nanjing Qinheng Microelectronics Co., Ltd.
* SPDX-License-Identifier: Apache-2.0
*******************************************************************************/
/*
*@Note
GPIO例程：
PA0推挽输出。
*/
#include "debug.h"
/* Global define */
/* Global Variable */
void USART3_IRQHandler(void) __attribute__((interrupt("WCH-Interrupt-fast")));
/*********************************************************************
* @fn GPIO_Toggle_INIT
*
* @brief Initializes GPIOA.0
*
* @return none
*/
void GPIO_Toggle_INIT(void) {
GPIO_InitTypeDef GPIO_InitStructure = { 0 };
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA, &GPIO_InitStructure);
}
void USART3_Init(void) {
int parity = USART_Parity_No;
//ToDo: for RS485 in nonParity stop bit should be 2
int stopBit = USART_StopBits_1;
int dataBit = USART_WordLength_8b;
u32 ulBaudRate = 9600;
GPIO_InitTypeDef GPIO_InitStructure = { 0 };
USART_InitTypeDef USART_InitStructure = { 0 };
NVIC_InitTypeDef NVIC_InitStructure = { 0 };
RCC_APB1PeriphClockCmd(
#ifdef USE_UART2
RCC_APB1Periph_USART2 |
#endif
RCC_APB1Periph_USART3, ENABLE);
//RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);
#ifdef USE_UART2
/* USART2 TX-->A.2 RX-->A.3 */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_Init(GPIOA, &GPIO_InitStructure);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
GPIO_Init(GPIOA, &GPIO_InitStructure);
#endif
/* USART3 TX-->B.10 RX-->B.11 */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_Init(GPIOB, &GPIO_InitStructure);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
GPIO_Init(GPIOB, &GPIO_InitStructure);
// ULONG ulBaudRate, UCHAR ucDataBits, eMBParity eParity
USART_InitStructure.USART_BaudRate = ulBaudRate; //115200;
USART_InitStructure.USART_WordLength = dataBit; //USART_WordLength_8b;
USART_InitStructure.USART_StopBits = stopBit; //USART_StopBits_1;
USART_InitStructure.USART_Parity = parity; //USART_Parity_No;
USART_InitStructure.USART_HardwareFlowControl =
USART_HardwareFlowControl_None;
USART_InitStructure.USART_Mode = USART_Mode_Tx | USART_Mode_Rx;
#ifdef USE_UART2
USART_Init(USART2, &USART_InitStructure);
USART_ITConfig(USART2, USART_IT_RXNE, ENABLE);
#endif
USART_Init(USART3, &USART_InitStructure);
USART_ITConfig(USART3, USART_IT_RXNE, ENABLE);
#ifdef USE_UART2
NVIC_InitStructure.NVIC_IRQChannel = USART2_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
#endif
NVIC_InitStructure.NVIC_IRQChannel = USART3_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 2;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
#ifdef USE_UART2
USART_Cmd(USART2, ENABLE);
#endif
USART_Cmd(USART3, ENABLE);
}
/*********************************************************************
* @fn USART3_IRQHandler
*
* @brief This function handles USART3 global interrupt request.
*
* @return none
*/
void USART3_IRQHandler(void) {
//printf("IRQ\r\n");
//RX not empty, data came
if (USART_GetITStatus(USART3, USART_IT_RXNE) != RESET) {
u16 d = USART_ReceiveData(USART3);
printf("%c", d);
USART_SendData(USART3, d);
//USART_ClearITPendingBit(USART3, USART_IT_RXNE);
}
//USART_IT_TC or USART_IT_TXE?
// TC: tramsimit done
// USART_IT_TXE : TX done, TX buffer empty
// From name "prvvUARTTxReadyISR" should be the TXE
else if (USART_GetITStatus(USART3, USART_IT_TC) != RESET) {
printf("U3 IRQ TX\r\n");
USART_ClearITPendingBit(USART3, USART_IT_TC);
} else {
printf("U3 Interrupt flag:\r\n");
if (USART_GetITStatus(USART3, USART_IT_CTS) != RESET) {
printf(" USART_IT_CTS ");
} else if (USART_GetITStatus(USART3, USART_IT_LBD) != RESET) {
printf(" USART_IT_LBD ");
} else if (USART_GetITStatus(USART3, USART_IT_TXE) != RESET) {
printf(" USART_IT_TXE ");
} else if (USART_GetITStatus(USART3, USART_IT_TC) != RESET) {
printf(" USART_IT_LBD ");
} else if (USART_GetITStatus(USART3, USART_IT_IDLE) != RESET) {
printf(" USART_IT_IDLE ");
} else if (USART_GetITStatus(USART3, USART_IT_ORE_RX) != RESET) {
printf(" USART_IT_ORE_RX ");
} else if (USART_GetITStatus(USART3, USART_IT_ORE_ER) != RESET) {
printf(" USART_IT_ORE_ER ");
} else if (USART_GetITStatus(USART3, USART_IT_NE) != RESET) {
printf(" USART_IT_NE ");
} else if (USART_GetITStatus(USART3, USART_IT_FE) != RESET) {
printf(" USART_IT_FE ");
} else if (USART_GetITStatus(USART3, USART_IT_PE) != RESET) {
printf(" USART_IT_PE ");
} else {
printf("Other UART Flag\r\n");
}
printf("\r\n");
}
}
/*********************************************************************
* @fn main
*
* @brief Main program.
*
* @return none
*/
int main(void) {
u8 i = 0;
u8 j = 1;
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
Delay_Init();
USART3_Init();
USART_Printf_Init(115200);
printf("SystemClk:%d\r\n", SystemCoreClock);
printf("GPIO Toggle TEST\r\n");
GPIO_Toggle_INIT();
while(1)
{
Delay_Ms(250);
GPIO_WriteBit(GPIOA, GPIO_Pin_0, (i == 0) ? (i = Bit_SET) : (i = Bit_RESET));
//GPIO_WriteBit(GPIOA, GPIO_Pin_1, (j == 0) ? (j = Bit_SET) : (j = Bit_RESET));
}
}
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