(This article was originally written in Chinese. To see an English version, please go to the bottom of the page and click on the Translate button.)

问题

如何使用Inter-Pan消息实现两个不同网络的设备之间的单跳通信？

答案

Inter-Pan消息可用于不同网络，同一信道的两个设备之间的单跳通信。Silicon Labs提供Inter-Pan Plugin，方便客户在此Plugin的基础上扩展，以在自己的应用中实现Inter-Pan消息的发送和接收。本文主要介绍如何搭建和测试Inter-Pan的功能，并以Z3Light sample（EmberZnet stack v5.10）为例，在WSTK+4151 无线板子上进行演示。

1. Inter-Pan Plugin的源码位于协议栈的C:\SiliconLabs\SimplicityStudio\v4\developer\sdks\gecko_sdk_suite\v1.1\protocol\zigbee_5.10\app\framework\plugin\interpan

1. 在Z3Light sample中已经勾选该Inter-Pan Plugin。创建并编译该Z3Light sample，将固件以及对应的Bootloader烧录到两块WSTK 4151无线板。

1. 两块无线板启动之后会自动扫描网络并加入Centralized，如果没有网络可以加入，最后会建立自己Distributed网络。在此实验中，每个板子分别建立自己的Distributed网络，确保它们处于同一个信道即可。如果比较难建立同一信道上的不同网络，也可以分别加入两个同一信道不同PANID的网络。如下所示，两个板子分别建立好自己的网络。

AppBuilder MFG Code: 0x1002
node [(>)000B57FFFE07F6E3] chan [20] pwr [3]
panID [0xF052] nodeID [0xCBD9] xpan [0x(>)0D03351F0A0587C6]
stack ver. [5.10.0 GA build 36]
nodeType [0x02]
Security level [05]
network state [02] Buffs: 74 / 75

AppBuilder MFG Code: 0x1002
node [(>)000B57FFFE07F6E2] chan [20] pwr [3]
panID [0x2923] nodeID [0x390E] xpan [0x(>)87461289F0783C2F]
stack ver. [5.10.0 GA build 36]
nodeType [0x02]
Security level [05]
network state [02] Buffs: 75 / 75

1. 通过CLI命令测试Inter-Pan消息的发送和接收。在Simplicity Studio中，将两个设备对应的Console打开，在一个Console中输入如下命令：

plugin interpan fragment-test [panId:2] [eui64:8] [clusterId:2] [msgLen:2]

• Sends a message of specified length of random values to target device over inter-PAN.
  • panId - INT16U - The PAN ID that the target is located on
  • eui64 - IEEE_ADDRESS - The target's EUI64 (big endian)
  • clusterId - INT16U - The cluster ID that the sample message should contain
  • msgLen - INT16U - The length of the randomly-filled message to be sent across inter-PAN

plugin interpan fragment-test 0xFFFF {000B57FFFE07F6E3}  0x0000 10

其中第一个参数是目的设备的PANID，可以设置为0xFFFF。

第二个参数是目的设备的EUI64，可以设置为NULL代表广播消息，否则为单播。

第三个参数是目的设备的Cluster。

第四个参数是发送的消息的Playload长度。

1. 发送完上述命令，可在控制台中看到对应的输出信息：

发送端：

Z3LightSocV510MG1>Sending inter-PAN message of len 10 to (>)000B57FFFE07F6E3 with random values: T00000000:Inter-PAN TX (10) [A9 30 09 70 82 6D D1 A9 3B 14 ], 0x00
success (0x00)

接收端：

RX inter-PAN message (unicast):
  src pan id: 0x2923
  src long id: (>)000B57FFFE07F6E2
  profile id: 0x0109
  cluster id: 0x0000 (Basic)
ERR: Inter-PAN profile 0x0109, cluster 0x0000, command 0x09 not permitted

以上打印信息表明Inter-Pan消息发送成功。用户可根据自己的需求，构建自定义的消息。

1. 函数流程分析：

发送流程：

当输入plugin interpan fragment-test，最调用如下函数：

void emAfInterpanFragmentTestCommand(void)

|-- emberAfSendInterPan()

|-- emberAfInterpanSendMessageCallback()

    |-- makeInterPanMessage()

    |-- emAfPluginInterpanSendRawMessage()

        |-- emberSendRawMessage()

最核心的函数是emberSendRawMessage()，其在raw-message.h中定义。

/** @brief Sends the given message over the air without higher layer
 * network headers.
 *
 * The first two bytes are interpreted as the 802.15.4 frame control field.
 * If the Ack Request bit is set, the packet will be retried as necessary.
 * Completion is reported via ::emberRawTransmitCompleteHandler().
 * Note that the sequence number specified in this packet is not taken into
 * account by the MAC layer. The MAC layer overwrites the sequence number field
 * with the next available sequence number.
 *
 * @param message  The message to transmit.
 *
 * @return ::EMBER_SUCCESS if the message was successfully submitted to
 * the transmit queue, and ::EMBER_ERR_FATAL otherwise.
 */
EmberStatus emberSendRawMessage(EmberMessageBuffer message);

如果想发送广播消息， 可将emberAfSendInterPan()的参数改为如下格式：

EmberStatus status = emberAfSendInterPan( OxFFFF,
                     NULL,
                     EMBER_NULL_NODE_ID,
                     0,      // mcast id - unused
                     clusterId,
                     SE_PROFILE_ID, // GBCS only
                     messageLen,
                     testMessage);

接收流程：

当接收到Inter-Pan消息时，emberMacPassthroughFilterHandler()会被调用，其在raw-message.h中定义。

/** @brief This function is called when the stack has received a raw MAC message that has
 *    matched one of the application's configured MAC filters.
 *
 * @param macFilterMatchStruct This is a pointer to a structure containing information
 *   about the matching message, including the index of the filter that was matched,
 *   and the actual data of the message.
 */
void emberMacFilterMatchMessageHandler(const EmberMacFilterMatchStruct* macFilterMatchStruct);

emberMacFilterMatchMessageHandler()

    |-- emAfPluginInterpanProcessMessage()

        |-- emberAfPluginInterpanPreMessageReceivedCallback()

以上就是Inter-Pan消息的测试过程以及发送和接收流程的源码分析，更多信息请参考Inter-Pan Plugin的源码。

The scheduled transmit/receive operations are designed to start at the exact time that you specify and RAIL accounts for any transition times and ramp times it knows about. In BLE, RAIL also has Rx and Tx chain delay values that make these times very accurate. In proprietary PHYs RAIL do not have the Rx and Tx chain delays so there may be some small error, but the timings should be pretty close.

Also, RAIL is only taking the idleToTx time for transmit and idleToRx time for receive into account. If the radio happens to be in a state other than idle, it will be subjected to the rxToTx or txToRx times which could be different and cause a scheduled operation to start at the wrong time. So, for now, those numbers just need to be set the same to ensure proper behavior.