rosserial_python serial_node.py分析--补遗

上位机会每隔2秒左右发送一个帧, 看帧id, 其实是0x0A, 就是时间, 那么问题来了, 后面8个字节怎么表示的时间呢?

    def handleTimeRequest(self, data):
        """ Respond to device with system time. """
        t = Time()
        t.data = rospy.Time.now()
        data_buffer = StringIO.StringIO()
        t.serialize(data_buffer)
        self.send( TopicInfo.ID_TIME, data_buffer.getvalue() )
        self.lastsync = rospy.Time.now()

查Time.h文件, 发现序列化的方法是:

    virtual int serialize(unsigned char *outbuffer) const
    {
      int offset = 0;
      *(outbuffer + offset + 0) = (this->data.sec >> (8 * 0)) & 0xFF;
      *(outbuffer + offset + 1) = (this->data.sec >> (8 * 1)) & 0xFF;
      *(outbuffer + offset + 2) = (this->data.sec >> (8 * 2)) & 0xFF;
      *(outbuffer + offset + 3) = (this->data.sec >> (8 * 3)) & 0xFF;
      offset += sizeof(this->data.sec);
      *(outbuffer + offset + 0) = (this->data.nsec >> (8 * 0)) & 0xFF;
      *(outbuffer + offset + 1) = (this->data.nsec >> (8 * 1)) & 0xFF;
      *(outbuffer + offset + 2) = (this->data.nsec >> (8 * 2)) & 0xFF;
      *(outbuffer + offset + 3) = (this->data.nsec >> (8 * 3)) & 0xFF;
      offset += sizeof(this->data.nsec);
      return offset;
    }

这样就明了了, 8个bytes,有4个是小数点之前, 有4个是小数点之后的.

所以, "xc8x38x67x59x05xb6x2cx37", 其实是:

0x596738c8   .  xxxx, 放计算器里面一算, 就是1499936968.xxxx不重要了吧...

这样看来就没有设么问题了吧, 看来学点python不是没有好处.