基于RT-Thread实现can通讯例程讲解

首先粘贴出官方提供的can例程代码，根据需要我将部分内容做了修改，供大家参考！

can_sample中包换以下函数： 接收数据回调函数 static rt_err_t can_rx_call(rt_device_t dev, rt_size_t size)

定义can接收线程：static void can_rx_thread(void *parameter)

查找can设备：rt_device_t rt_device_find(const char* name);

打开can设备：rt_err_t rt_device_open(rt_device_t dev, rt_uint16_t oflags);

发生can数据：rt_size_t rt_device_write(rt_device_t dev, rt_off_t pos, const void* buffer, rt_size_t size);

在int can_sample(int argc, char *argv[])中调用can接收线程

其中对于描述是有两个段代码可供参考

/*
 * 程序清单：这是一个 CAN 设备使用例程
 * 例程导出了 can_sample 命令到控制终端
 * 命令调用格式：can_sample can1
 * 命令解释：命令第二个参数是要使用的 CAN 设备名称，为空则使用默认的 CAN 设备
 * 程序功能：通过 CAN 设备发送一帧，并创建一个线程接收数据然后打印输出。
*/
#include 
#include "rtdevice.h"
#define CAN_DEV_NAME       "can1"      /* CAN 设备名称 */
static struct rt_semaphore rx_sem;     /* 用于接收消息的信号量 */
static rt_device_t can_dev;            /* CAN 设备句柄 */
/* 接收数据回调函数 */
static rt_err_t can_rx_call(rt_device_t dev, rt_size_t size)
{
    /* CAN 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(&rx_sem);
    return RT_EOK;
}
static void can_rx_thread(void *parameter)
{
    int i;
    rt_err_t res;
    struct rt_can_msg rxmsg = {0};
    /* 设置接收回调函数 */
    rt_device_set_rx_indicate(can_dev, can_rx_call);

    while (1)
    {
        /* hdr 值为 - 1，表示直接从 uselist 链表读取数据 */
        rxmsg.hdr = -1;
        /* 阻塞等待接收信号量 */
        rt_sem_take(&rx_sem, RT_WAITING_FOREVER);
        /* 从 CAN 读取一帧数据 */
        rt_device_read(can_dev, 0, &rxmsg, sizeof(rxmsg));
        /* 打印数据 ID 及内容 */
        rt_kprintf("ID:%x", rxmsg.id);
        for (i = 0; i < 8; i++)
        {
            rt_kprintf("%2x", rxmsg.data[i]);
        }
        rt_kprintf("\n");
    }
}
int can_sample(int argc, char *argv[])
{
    struct rt_can_msg msg = {0};
    rt_err_t res;
    rt_size_t  size;
    rt_thread_t thread;
    char can_name[RT_NAME_MAX];
    if (argc == 2)
    {
        rt_strncpy(can_name, argv[1], RT_NAME_MAX);
    }
    else
    {
        rt_strncpy(can_name, CAN_DEV_NAME, RT_NAME_MAX);
    }
    /* 查找 CAN 设备 */
    can_dev = rt_device_find(can_name);
    if (!can_dev)
    {
        rt_kprintf("find %s failed!\n", can_name);
        return RT_ERROR;
    }
    /* 初始化 CAN 接收信号量 */
    rt_sem_init(&rx_sem, "rx_sem", 0, RT_IPC_FLAG_FIFO);
    /* 以中断接收及发送方式打开 CAN 设备 */
    res = rt_device_open(can_dev, RT_DEVICE_FLAG_INT_TX | RT_DEVICE_FLAG_INT_RX);
    RT_ASSERT(res == RT_EOK);
    /* 创建数据接收线程 */
    thread = rt_thread_create("can_rx", can_rx_thread, RT_NULL, 1024, 25, 10);
    if (thread != RT_NULL)
    {
        rt_thread_startup(thread);
    }
    else
    {
        rt_kprintf("create can_rx thread failed!\n");
    }
    msg.id = 0x78;              /* ID 为 0x78 */
    msg.ide = RT_CAN_STDID;     /* 标准格式 */
    msg.rtr = RT_CAN_DTR;       /* 数据帧 */
    msg.len = 8;                /* 数据长度为 8 */
    /* 待发送的 8 字节数据 */
    msg.data[0] = 0x00;
    msg.data[1] = 0x11;
    msg.data[2] = 0x22;
    msg.data[3] = 0x33;
    msg.data[4] = 0x44;
    msg.data[5] = 0x55;
    msg.data[6] = 0x66;
    msg.data[7] = 0x77;
    /* 发送一帧 CAN 数据 */
    size = rt_device_write(can_dev, 0, &msg, sizeof(msg));
    if (size == 0)
    {
        rt_kprintf("can dev write data failed!\n");
    }
    return res;
}
void can_send_test(void)
{
    struct rt_can_msg msg = {0};
    rt_size_t  size;
    static rt_uint8_t num = 0;
    msg.id = 0x78;              /* ID 为 0x78 */
    msg.ide = RT_CAN_STDID;     /* 标准格式 */
    msg.rtr = RT_CAN_DTR;       /* 数据帧 */
    msg.len = 8;                /* 数据长度为 8 */
    /* 待发送的 8 字节数据 */
    msg.data[0] = 0x00;
    msg.data[1] = num++;     //can发送数据随意更改
    msg.data[2] = 0x22;
    msg.data[3] = 0x33;
    msg.data[4] = num++;
    msg.data[5] = 0x55;
    msg.data[6] = 0x66;
    msg.data[7] = 0x77;
    /* 发送一帧 CAN 数据 */
    size = rt_device_write(can_dev, 0, &msg, sizeof(msg));
    if (size == 0)
    {
        rt_kprintf("can dev write data failed!\n");
    }
}
/* 导出到 msh 命令列表中 */
MSH_CMD_EXPORT(can_sample, can device sample);
MSH_CMD_EXPORT(can_send_test, can send test);

另外一个版本，实现的功能是一样的

/*
 * 程序清单：这是一个 CAN 设备使用例程
 * 例程导出了 can_sample 命令到控制终端
 * 命令调用格式：can_sample can1
 * 命令解释：命令第二个参数是要使用的 CAN 设备名称，为空则使用默认的 CAN 设备
 * 程序功能：通过 CAN 设备发送一帧，并创建一个线程接收数据然后打印输出。
*/

#include 
#include "rtdevice.h"

#define CAN_DEV_NAME       "can1"      /* CAN 设备名称 */

static struct rt_semaphore rx_sem;     /* 用于接收消息的信号量 */
static rt_device_t can_dev;            /* CAN 设备句柄 */

#define THREAD_PRIORITY         25
#define THREAD_STACK_SIZE       512
#define THREAD_TIMESLICE        5

static rt_thread_t tid1 = RT_NULL;

/* 接收数据回调函数 */
static rt_err_t can_rx_call(rt_device_t dev, rt_size_t size) {
    /* CAN 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(&rx_sem);

    return RT_EOK;
}

static void can_rx_thread(void *parameter) {
    int i;
    rt_err_t res;
    struct rt_can_msg rxmsg = {0};

    /* 设置接收回调函数 */
    rt_device_set_rx_indicate(can_dev, can_rx_call);

    while (1) {
        /* hdr 值为 - 1，表示直接从 uselist 链表读取数据 */
        rxmsg.hdr = -1;
        /* 阻塞等待接收信号量 */
        rt_sem_take(&rx_sem, RT_WAITING_FOREVER);
        /* 从 CAN 读取一帧数据 */
        rt_device_read(can_dev, 0, &rxmsg, sizeof(rxmsg));
        /* 打印数据 ID 及内容 */
        rt_kprintf("ID:%x", rxmsg.id);
        for (i = 0; i < 8; i++) {
            rt_kprintf("%2x", rxmsg.data[i]);
        }

        rt_kprintf("\n");
    }
}

/* 线程 1 的入口函数 */
static void thread1_entry(void *parameter) {
    struct rt_can_msg msg = {0};
    unsigned long count = 0;

    msg.id = 0x78;              /* ID 为 0x78 */
    msg.ide = RT_CAN_STDID;     /* 标准格式 */
    msg.rtr = RT_CAN_DTR;       /* 数据帧 */
    msg.len = 8;                /* 数据长度为 3 */
    /* 待发送的 3 字节数据 */
    msg.data[0] = 0x00;
    msg.data[1] = 0x11;
    msg.data[2] = 0x22;
    msg.data[3] = 0x00;
    msg.data[4] = 0x11;
    msg.data[5] = 0x00;
    msg.data[6] = 0x11;
    msg.data[7] = 0x22;

    rt_kprintf("send %ld \n", ++count);

    while (1) {
        /* 线程 1 采用低优先级运行，一直打印计数值 */
        rt_device_write(can_dev, 0, &msg, sizeof(msg));
        rt_kprintf("send %ld \n", ++count);
        rt_thread_mdelay(500);
    }
}



int can_sample(int argc, char *argv[]) {
    rt_err_t res;
    rt_size_t  size;
    rt_thread_t thread;
    char can_name[RT_NAME_MAX];

    if (argc == 2) {
        rt_strncpy(can_name, argv[1], RT_NAME_MAX);
    } else {
        rt_strncpy(can_name, CAN_DEV_NAME, RT_NAME_MAX);
    }

    /* 查找 CAN 设备 */
    can_dev = rt_device_find(can_name);
    if (!can_dev) {
        rt_kprintf("find %s failed!\n", can_name);
        return RT_ERROR;
    }

    /* 初始化 CAN 接收信号量 */
    rt_sem_init(&rx_sem, "rx_sem", 0, RT_IPC_FLAG_FIFO);

    /* 以中断接收及发送方式打开 CAN 设备 */

    res = rt_device_open(can_dev, RT_DEVICE_FLAG_INT_TX | RT_DEVICE_FLAG_INT_RX);
    /* 设置 CAN 的工作模式为正常工作模式 */
    res = rt_device_control(can_dev, RT_CAN_CMD_SET_MODE, (void *)RT_CAN_MODE_NORMAL);
    res = rt_device_control(can_dev, RT_CAN_CMD_SET_BAUD, (void *)CAN500kBaud);
    RT_ASSERT(res == RT_EOK);
    /* 创建数据接收线程 */
    thread = rt_thread_create("can_rx", can_rx_thread, RT_NULL, 1024, 25, 10);
    if (thread != RT_NULL) {
        rt_thread_startup(thread);
    } else {
        rt_kprintf("create can_rx thread failed!\n");
    }


    if (size == 0) {
        rt_kprintf("can dev write data failed!\n");
    }

    /* 创建线程 1，名称是 thread1，入口是 thread1_entry*/
    tid1 = rt_thread_create("thread1",
                            thread1_entry, RT_NULL,
                            THREAD_STACK_SIZE,
                            THREAD_PRIORITY, THREAD_TIMESLICE);

    /* 如果获得线程控制块，启动这个线程 */
    if (tid1 != RT_NULL)
        rt_thread_startup(tid1);
    else
        rt_kprintf("start can send fail\n");

    return res;
}
/* 导出到 msh 命令列表中 */
MSH_CMD_EXPORT(can_sample, can device sample);

代码编译完成，下载。串口运行：can_sample，打开创芯科技CAN卡，打开电脑的USB CAN工具

打开USB转CAN，选择对应波特率，这里配置为1Mbps。

重启，再次运行can_sample，发现，接收到STM32发出的CAN数据帧。

多次运行 can_send_test，电脑端可以接受数据。

审核编辑：汤梓红