10 想请教一下如何解决串口单总线半双工中在发送数据的同时也会收到消息的问题？

发布于 2022-08-20 16:38:25 浏览：515 订阅该版

串口收发是通过一个模块，此模块对外只有一根总线，发送时也会产生接收。
自定义的发送函数如下，发送时先关闭了串口中断，发送完毕后再开启中断，但实际显示一直在产生接收中断。
```c
/********************************** (C) COPYRIGHT *******************************
* File Name          : drv_cpp.c
* Author             : MXH
* Version            : V1.0.0
* Date               : 2022/08/10
* Description        : cpp program body.
*******************************************************************************/
#include "drv_cpp.h"
#define DRV_DEBUG
#include "drv_log.h"

/* semaphore used for rec */
#define CPP_RX_SEM_NAME  "cpp_rx_sem"
static rt_sem_t cpp_rx_sem = RT_NULL;

static rt_device_t cpp_dev = RT_NULL;
struct serial_configure cpp_init_config = {
        .baud_rate = BAUD_RATE_9600, /* 9600 bits/s */  \
        .data_bits = DATA_BITS_8,      /* 8 databits */     \
        .stop_bits = STOP_BITS_1,      /* 1 stopbit */      \
        .parity = PARITY_NONE,      /* No parity  */     \
        .bit_order = BIT_ORDER_LSB,    /* LSB first sent */ \
        .invert = NRZ_NORMAL,       /* Normal mode */    \
        .bufsz = RT_SERIAL_RB_BUFSZ, /* Buffer size */  \
        .flowcontrol = RT_SERIAL_FLOWCONTROL_NONE, /* Off flowcontrol */ \
        .reserved = 0,
};

#define CPP_THREAD_NAME         "cpp_thread"
#define CPP_THREAD_PRIORITY     25
#define CPP_THREAD_TIMESLICE    10
#define CPP_THREAD_STACKSIZE    1024
static rt_thread_t cpp_thread = RT_NULL;

rt_err_t drv_cpp_recv_cb(rt_device_t dev, rt_size_t size)
{
    /* 串口接收到数据后产生中断，调用此回调函数，然后发送接收信号量 */
    rt_sem_release(cpp_rx_sem);
    rt_kprintf("release.");

return RT_EOK;
}

static void cpp_thread_entry(void *parameter)
{
//    char cpp_recv[128];

while (1)
    {
        /* 从串口读取一个字节的数据，没有读取到则等待接收信号量 */
//        while (rt_device_read(cpp_dev, -1, cpp_recv, 128))
//        {
//            /* 阻塞等待接收信号量，等到信号量后再次读取数据 */
//            rt_sem_take(cpp_rx_sem, RT_WAITING_FOREVER);
//        }
        /* 读取到的数据通过串口错位输出 */
//        ch = ch + 1;

//        rt_device_control(cpp_dev, cmd, arg);

//        rt_device_write(cpp_dev, 0, &ch, 1);

//        rt_kprintf("%s", cpp_recv);
//        rt_device_write(cpp_dev, -1, "asdf", 4);
//        rt_thread_mdelay(2000);
    }
}

static int drv_cpp_init(void)
{
    int result = RT_EOK;

/* sem create */
    cpp_rx_sem = rt_sem_create(CPP_RX_SEM_NAME, 0, RT_IPC_FLAG_PRIO);
    if(RT_NULL == cpp_rx_sem)
    {
        LOG_E("init %s failed.", CPP_RX_SEM_NAME);
    }

/* cpp device init */
    cpp_dev = rt_device_find(CPP_CLI_NAME);
    if(RT_NULL == cpp_dev)
    {
        LOG_E("can't find device %s", CPP_CLI_NAME);
        return RT_ERROR;
    }

result = rt_device_control(cpp_dev, RT_DEVICE_CTRL_CONFIG, (void *)&cpp_init_config);
    if(RT_EOK != result)
    {
        LOG_E("can't control device %s", CPP_CLI_NAME);
        return RT_ERROR;
    }

//    rt_device_open(cpp_dev, RT_DEVICE_FLAG_RDWR | RT_DEVICE_FLAG_INT_RX);
    rt_device_open(cpp_dev, RT_DEVICE_FLAG_INT_RX);

rt_device_set_rx_indicate(cpp_dev, drv_cpp_recv_cb);     // set rx callback function

/* create and start cpp_thread */
    cpp_thread = rt_thread_create(CPP_THREAD_NAME, cpp_thread_entry, RT_NULL,
                                    CPP_THREAD_STACKSIZE, CPP_THREAD_PRIORITY, CPP_THREAD_TIMESLICE);
    if(RT_NULL == cpp_thread)
    {
        LOG_E("init thread %s failed.", CPP_THREAD_NAME);
        return RT_ERROR;
    }
    rt_thread_startup(cpp_thread);

return RT_EOK;
}
INIT_DEVICE_EXPORT(drv_cpp_init);

int drv_cpp_send(char *str)
{
    int result = RT_EOK;

rt_device_control(cpp_dev, RT_DEVICE_CTRL_CLR_INT, RT_NULL);
    result = rt_device_write(cpp_dev, -1, str, sizeof(str));
    rt_device_control(cpp_dev, RT_DEVICE_CTRL_SET_INT, RT_NULL);

return result;
}

```
想请教一下应该如何解决这种问题。。。