STM32F030R8 RS485半双工不传输

时间：2018-04-03 15:19:28

标签： c microcontroller stm32 rs485

我使用STM32F030R8执行连接到AD3485的RS485通信。到目前为止，我已经能够让它传输得很好，但是当我设置一个中断处理程序时，似乎中断是由我的芯片自己的传输触发并停止所有进一步的传输。

我错过了某处设置或清除标志吗？我在RS485初始化步骤中遗漏了什么吗？当我的传输不可避免地触发中断请求时，我应该清除标志吗？

下面我已经提到了一个非常精简但完整的代码版本，用于传输数据，以及我从RS485看到的数据捕获我连接到A9 A10和A12引脚的芯片。

以下是代码：

#include "stm32f0xx_conf.h"
#include <stm32f0xx_gpio.h>
#include <stm32f0xx_rcc.h>
#include <stm32f0xx_usart.h>

void SysTick_Handler(void) {

    while (USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET);
    USART_SendData(USART1, 0xAC);
    while(USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET);
    USART_SendData(USART1, 0x44);
    while(USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET);
    USART_SendData(USART1, 0x04);
    while(USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET);
    USART_SendData(USART1, 0x53);
    while(USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET);

}

void RS485_Init(){
    GPIO_InitTypeDef GPIO_InitStruct;
    USART_InitTypeDef USART_InitStruct;
    NVIC_InitTypeDef NVIC_InitStruct;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);

    GPIO_InitStruct.GPIO_Pin = GPIO_Pin_9 | GPIO_Pin_10 | GPIO_Pin_12; // Pins 9 (TX) 10 (RX) 12 (DE) 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(GPIOA, &GPIO_InitStruct);

    GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_1); //
    GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_1);
    GPIO_PinAFConfig(GPIOA, GPIO_PinSource12, GPIO_AF_1);

    USART_InitStruct.USART_BaudRate = 38400 ; // 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);

    USART_HalfDuplexCmd(USART1, ENABLE);
    USART_DECmd(USART1, ENABLE);
    USART_ITConfig(USART1, USART_IT_TXE, DISABLE);
    USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);
    USART_SetDEAssertionTime(USART1, 0x4E2);
    USART_SetDEDeassertionTime(USART1, 0x4E2);
    USART_DEPolarityConfig(USART1, USART_DEPolarity_High);

    NVIC_InitStruct.NVIC_IRQChannel = USART1_IRQn;
    NVIC_InitStruct.NVIC_IRQChannelPriority = 0;
    NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStruct); //When I comment this out, I'm able to transmit normally, but without an ISR receiving bytes will be difficult

    USART_Cmd(USART1, ENABLE);

}

//This function handles USART1 global interrupt request.
void USART1_IRQHandler(void)
{

    if(USART_GetITStatus(USART1, USART_IT_RXNE) != RESET){
        unsigned char USART_Temp_Byte;
        USART_ClearITPendingBit(USART1, USART_IT_RXNE);
        USART_Temp_Byte = (unsigned char) USART_ReceiveData(USART1); //receive a char
    }

}

int main(void)
{
    RS485_Init();
    SysTick_Config(SystemCoreClock/1000);
    while(1);
}

这里捕获了我启用中断（第一次捕获）的时间，以及当我注释掉NVIC_Init（＆amp; NVIC_InitStruct）时;并且没有ISR触发：

Logic capture of RS485 Transmission problem

2 个答案:

答案 0 :(得分：2)

这是半/全双工通信方法的核心原则之一。 RS485是一种物理层标准，允许发送器接收自己的数据。这对其他标准（软件层）很有用，例如J1708。由于不需要单个主设备和多个从设备，因此每个节点都可以启动通信。如果两个模块同时开始通话，则需要有一个方案来检测和处理总线争用/冲突。使用RS485，您具有支配（驱动）状态和隐性（非驱动）状态。当发射器开始发射时，您监视以查看您收到的内容是否与您发送的内容相匹配，如果不匹配，则很可能是另一台设备试图同时发送。这是有效的，因为当你从支配状态切换到隐性状态时，总线将返回到隐性状态（没有碰撞），或者由于另一个接收器保持线路（碰撞）而保持在支配状态。发生这种情况时，您将停止任何进一步的传输，并开始接收或监控总线的空闲状态。大多数协议，如J1708，使用基于您的地址的伪随机生成器来计算重试延迟，这可以防止相同的两个模块不断发生冲突。 长话短说：你收到你传送的东西这是一件好事。我建议你使用中断来比较刚发送的字节和刚收到的字节，如果它们匹配，发送下一个字节，否则终止并在检测到下一个空闲状态后再试一次。由于它是相同的中断例程，您需要设置一个标志，指示何时发送和控制中断逻辑以处理比较（Tx部分）或处理正常接收（Rx部分）

答案 1 :(得分：0)

我添加此答案作为更新，以使半双工通信与此特定芯片一起使用。通过这种配置，我能够发送和接收。特别感谢Joe Thomas让我走上正轨。

#include "stm32f0xx_conf.h"
#include <stm32f0xx_gpio.h>
#include <stm32f0xx_rcc.h>
#include <stm32f0xx_usart.h>

void Transmit(void){

    USART_Cmd(USART1, DISABLE);
    USART_DECmd(USART1, ENABLE);
    USART_ITConfig(USART1, USART_IT_TXE, ENABLE);
    USART_ITConfig(USART1, USART_IT_RXNE, DISABLE);
    USART_Cmd(USART1, ENABLE);

    while (USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET);

    USART_SendData(USART1, 0xAC);
    while(USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET);
    while (USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET);

    USART_SendData(USART1, 0x44);
    while(USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET);
    while (USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET);

    USART_SendData(USART1, 0x04);
    while(USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET);
    while (USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET);

    USART_SendData(USART1, 0x53);
    while(USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET);
    while (USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET);

    USART_Cmd(USART1, DISABLE);
    USART_DECmd(USART1, DISABLE);
    USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);
    USART_ITConfig(USART1, USART_IT_TXE, DISABLE);
    USART_Cmd(USART1, ENABLE);

}

void SysTick_Handler(void) {

}

void RS485_Init(){

    GPIO_InitTypeDef GPIO_InitStruct;
    USART_InitTypeDef USART_InitStruct;
    NVIC_InitTypeDef NVIC_InitStruct;



    RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);

    GPIO_InitStruct.GPIO_Pin = GPIO_Pin_9 | GPIO_Pin_10 | GPIO_Pin_12;
    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;
    GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
    GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_UP;
    GPIO_Init(GPIOA, &GPIO_InitStruct);

    GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_1);
    GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_1);
    GPIO_PinAFConfig(GPIOA, GPIO_PinSource12, GPIO_AF_1);

    USART_DeInit(USART1);
    USART_StructInit(&USART_InitStruct);
    USART_InitStruct.USART_BaudRate = 38400 ;
    USART_InitStruct.USART_WordLength = USART_WordLength_8b;
    USART_InitStruct.USART_StopBits = USART_StopBits_1;
    USART_InitStruct.USART_Parity = USART_Parity_No;
    USART_InitStruct.USART_HardwareFlowControl = USART_HardwareFlowControl_RTS;
    USART_InitStruct.USART_Mode = USART_Mode_Tx | USART_Mode_Rx;
    USART_Init(USART1, &USART_InitStruct);

    USART_HalfDuplexCmd(USART1, DISABLE);
    USART_DECmd(USART1, DISABLE);
    USART_ITConfig(USART1, USART_IT_TXE, DISABLE);
    USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);
    USART_SetDEAssertionTime(USART1, 0x4E2);
    USART_SetDEDeassertionTime(USART1, 0x4E2);
    USART_DEPolarityConfig(USART1, USART_DEPolarity_High);



    NVIC_InitStruct.NVIC_IRQChannel = USART1_IRQn;
    NVIC_InitStruct.NVIC_IRQChannelPriority = 0;
    NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStruct);

    USART_ClearITPendingBit(USART1, USART_IT_RXNE);
    USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);

    USART_Cmd(USART1, ENABLE);

}

void USART1_IRQHandler(void)
{

    if(USART_GetITStatus(USART1, USART_IT_RXNE) != RESET){
        unsigned char USART_Temp_Byte;
        USART_ClearITPendingBit(USART1, USART_IT_RXNE);
        USART_Temp_Byte = (unsigned char) USART_ReceiveData(USART1); //receive a char
        if(0x53 == USART_Temp_Byte){
            Transmit();
        }
    }

}

int main(void)
{
    RS485_Init();
    SysTick_Config(SystemCoreClock/1000);
    while(1){};
}
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