convert CAN frame

前言

最近了解了一些socket can的知识点，本文主要介绍如何将数据转换为CAN报文，前提是已经确定CAN的传输协议。

本文使用的CAN报文共有22条，这些报文共用一个can id，每条报文使用序号标志；

报文协议

转换数据程序

char* convert_buf(vector<Point>& probp, vector<Distance>& pdist, vector<int>& plabel)
{
    //convert-can-frame.
    char buffer[22][8] = { 0 };
    for (int i = 0; i < 22; i++)
    {
        double lat_factor = 0.1;
        double long_factor = 0.2;

        unsigned int lat01 = static_cast<unsigned int>(pdist[3 * i].x_dis / lat_factor);//unit-2dm-8bits.
        unsigned int long01 = static_cast<unsigned int>(pdist[3 * i].y_dis / long_factor);//unit-2dm-9bits.
        int label01 = plabel[i*3];

        if (i == 21)
        {
            buffer[i][0] = (((i+1) & 0xFF) << 3) + ((long01 & 0x1FF) >> 6);
            buffer[i][1] = ((long01 & 0x1FF) << 2) + ((lat01 & 0xFF) >> 6);
            buffer[i][2] = ((lat01 & 0xFF) << 2) + (label01 & 0x03);
            break;
        }

        unsigned int lat02 = static_cast<unsigned int>(pdist[3 * i + 1].x_dis / lat_factor);//unit-2dm-8bits.
        unsigned int long02 = static_cast<unsigned int>(pdist[3 * i + 1].y_dis / long_factor);//unit-2dm-9bits.
        int label02 = plabel[3 * i + 1];

        unsigned int lat03 = static_cast<unsigned int>(pdist[3 * i + 2].x_dis / lat_factor);//unit-2dm-8bits.
        unsigned int long03 = static_cast<unsigned int>(pdist[3 * i + 2].y_dis / long_factor);//unit-2dm-9bits.
        int label03 = plabel[3 * i + 2];

        std::cout << "long01 --- " << long01 << "-- long02 --- " << long02 << "--- long03 --- " << long03 << std::endl;
        buffer[i][0] = (((i + 1) & 0xFF) << 3) + ((long01 & 0x1FF) >> 6);
        buffer[i][1] = ((long01 & 0x1FF) << 2) + ((lat01 & 0xFF) >> 6);
        buffer[i][2] = ((lat01 & 0xFF) << 2) + (label01 & 0x03);
        buffer[i][3] = ((long02 & 0x1FF) >> 1);
        buffer[i][4] = ((long02 & 0x1FF) << 7) + ((lat02 & 0xFF) >> 1);
        buffer[i][5] = ((lat02 & 0xFF) << 7) + ((label02 & 0x03) << 5) + ((long03 & 0x1FF) >> 4);
        buffer[i][6] = ((long03 & 0x1FF) << 4) + ((lat03 & 0xFF) >> 4);
        buffer[i][7] = ((lat03 & 0xFF) << 4) + ((label03 & 0x03) << 2);

        printf("buffer[0]: --- %x\n", (byte)buffer[i][0]);
        printf("buffer[1]: --- %x\n", (byte)buffer[i][1]);
        printf("buffer[2]: --- %x\n", (byte)buffer[i][2]);
        printf("buffer[3]: --- %x\n", (byte)buffer[i][3]);
        printf("buffer[4]: --- %x\n", (byte)buffer[i][4]);
        printf("buffer[5]: --- %x\n", (byte)buffer[i][5]);
        printf("buffer[6]: --- %x\n", (byte)buffer[i][6]);
        printf("buffer[7]: --- %x\n", (byte)buffer[i][7]);

    }
    cout << "sizeof(buffer): " << sizeof(buffer) << " Byte..." << endl;
    return buffer[0];

}

注意

1.如何确定CAN协议的格式，特别是信号的范围、精度以及比特位数；

2.浮点型数据如何变换为可以进行逻辑运算和位移操作的数据类型；

3.如何按照报文格式得到每个字节的内容，特别是位移操作；

4.如何将报文内容正确输出方便查看；

5.原始数据可能越界，应该在转换为报文数据之前对原始数据进行越界处理；

6.转换为CAN报文过程中的各个操作符号的优先级；

完