Arduino串口读取目标检测结果
=======================================

适用产品
---------------
拥有串口的摄像头：

- SingTown AI Vision Module SC（yes）
- SingTown AI Vision Module EC（no）

目的
---------------
使用Arduino，通过串口获取 SingTown AI Vision Module 的目标检测识别结果。


前提条件
----------------------
模型已上传到摄像头

连接电路
----------------------
- SingTown AI Vision Module RX 不连接
- SingTown AI Vision Module TX 连接 Arduino D10
- SingTown AI Vision Module GND 连接 Arduino GND
- SingTown AI Vision Module VIN 连接 Arduino 5V (可选)


运行Arduino的代码
----------------------
代码下载：

- GitHub: https://github.com/SingTown/singtown-ai-cam-arduino-example/blob/main/read_singtownaicam_objs.ino
- 直接下载：:download:`download </media/singtown-ai-cam-arduino-example-main.zip>`.

代码介绍：

.. code :: arduino

    #define OBJECT_MAX 8    // Max Found 8 Objects
    #define OBJECT_SIZE 10  // Every Object is 10 bytes

    struct DetectObj {
      int score;  // max 255
      int idx;
      int x1;  // box left coordinate, max 640
      int y1;  // box top coordinate, max 480
      int x2;  // box right coordinate, max 640
      int y2;  // box bottom coordinate, max 480
    };

    struct DetectObj objs[OBJECT_MAX];

全局变量 objs ，用于存放读取的结果。

.. code :: arduino

    int check_crc(unsigned char* payload) {
      unsigned char num = payload[0];
      unsigned char crc = 0;
      int i = 0, j = 0;
      for (i = 0; i < num * OBJECT_SIZE + 2; i++) {
        crc ^= payload[i];
        for (j = 0; j < 8; j++) {
          if (crc & 1)
            crc ^= 0x91;
          crc >>= 1;
        }
      }
      return crc;
    }

check_crc 为校验函数，用于校验数据帧是否正确。

.. code :: arduino

    int read_singtownaicam_objs() {
      int i;
      unsigned char num;
      unsigned char payload[OBJECT_MAX * OBJECT_SIZE + 2];
      unsigned char* obj_ptr;
      int byte;
      while (1) {
        if (readByte() != 0xeb) continue;
        if (readByte() != 0x90) continue;

        num = readByte();
        if (num < 0 || num > OBJECT_MAX)
          continue;
        payload[0] = num;

        for (i = 1; i < num * OBJECT_SIZE + 2; i++) {
          byte = readByte();
          if (byte == -1) break;
          payload[i] = byte;
        }

        if (check_crc(payload) != 0) continue;

        for (i = 0; i < num; i++) {
          obj_ptr = payload + i * OBJECT_SIZE + 1;
          objs[i].score = obj_ptr[0];
          objs[i].idx = obj_ptr[1];
          objs[i].x1 = obj_ptr[2] | (obj_ptr[3] << 8);
          objs[i].y1 = obj_ptr[4] | (obj_ptr[5] << 8);
          objs[i].x2 = obj_ptr[6] | (obj_ptr[7] << 8);
          objs[i].y2 = obj_ptr[8] | (obj_ptr[9] << 8);
        }
        return num;
      }
    }

read_singtownaicam_objs 是读取数据函数，结果存放在 objs 全局变量中。