802..15.4(zigbee协议)

作者：下家山

一：802.15.4帧格式

图一

1.1 Preamble Sequence

此字段包含4个字节，有cc2420自动产生。

1.2 Start of Frame Delimiter

此字段包含1个字节，有cc2420自动产生。

   =============================================================================

1.3 Mac Protocol Data Unit

         接下来的字段是我们需要设置的

二：结构体表示MPDU

通常我们用一个结构体来表示

typedef struct

{

  /* The following fields are transmitted/received on the radio. */

  char length;

  char fcfhi;

  char fcflo;

  char dsn;

  int destpan;

  int addr;

  char type;

  char group;

  char Txdata[TOSH_DATA_LENGTH];

  /* The following fields are not actually transmitted or received

   * on the radio! They are used for internal accounting only.

   * The reason they are in this structure is that the AM interface

   * requires them to be part of the TOS_Msg that is passed to

   * send/receive operations.

   */

  char strength;

  char lqi;

  int crc;

  int ack;

  int time;//

} Msg;

如果，我们要发送一个字节0x55，程序该怎么写：

#define CC2420_DEF_FCF_LO          0x08

#define TOS_BCAST_ADDR             0xffff

#define CC2420_DEF_FCF_HI_ACK      0x21  // with ACK

#define CC2420_DEF_FCF_HI          0x01  // without ACK

void main()

{

 WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT

 hardwareinit();

 Msg * data;

 long int i,j;

 data=(Msg*)malloc(sizeof(Msg));

 P5DIR|=0X70;//0111 0000 1out 0 in

 P5OUT|=0X70; //1高电平                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          

 data -> length = 12;  //msg data length:10   last lqi&rssi:2

 data -> fcflo = CC2420_DEF_FCF_LO;//destination address mode:10

 data -> fcfhi = CC2420_DEF_FCF_HI_ACK;//ack request:1 frame type:10

// destination PAN is broadcast

 data -> destpan = TOS_BCAST_ADDR;

 // adjust the destination address to be in the right byte order

 data -> addr = 0x0001;

 // adjust the data type if need

 data -> type = FRAME_TYPE_DATA;

 // keep the DSN increasing for ACK recognition

 data -> dsn = 1;

 // reset the time field

 data -> time = 0;

data -> group=0x00;

data -> Txdata[0]=0x55;

for(i=0;i<100;i++)

{

 data->dsn =i;

  sendAMessage(data -> length,(char*)data);

 for(j=0;j<50000;j++);

}

free(data);

P5OUT|=0X10;

}

2.1发送数据截图

那么最终发送出去的数据是：

                                               图二

有了这些，我们可以把协议与代码，还有实际发送的数据一一对应起来

2.2 代码与发送数据汇总

2.3接收数据截图

那么接收到的数据呢？

首先，我们把发送与接收的数据的截图做一个比较：

三：怎么找到RSSI

那么我们MODEMCTRL0，AUTOCRC有没有被置位呢？

                                                                        2010-10-18 11:06  写于上海.松江

 (请尊重原创，转载请注明：作者，下家山)