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MQTT的移植

下载MQTT 嵌入式C/C++库：

本次项目是是MQTT在STM32f103设备上的移植，因此使用paho的嵌入式C库,源码地址GitHub - eclipse/paho.mqtt.embedded-c: Paho MQTT C client library for embedded systems. Paho is an Eclipse IoT project (https://iot.eclipse.org/)

移植：

 将以上文件全部移植到工程文件的协议层中去，然后参考../paho.mqtt.embedded-c/MQTTPacket/samples/中的例程编写代码。

修改接口函数

由于移植的FreeRTOS_Manual中没有”FreeRTOS_IP.h”和”FreeRTOS_Sockets.h”这两个头文件，因此需要修改MQTTFreeRTOS.c/.h中删除”FreeRTOS_IP.h”和”FreeRTOS_Sockets.h”，并修改Network结构体以及相关接口函数。

struct Network
 
{
 
  ptNetDev netdev;
 
int (*mqttread) (Network*, unsigned char*, int, int);
 
int (*mqttwrite) (Network*, unsigned char*, int, int);
 
void (*disconnect) (Network*);
 
};

接下来是FreeRTOS_read和FreeRTOS_write函数：

int FreeRTOS_read(Network* n, unsigned char* buffer, int len, int timeout_ms)
 
{
 
TickType_t xTicksToWait = timeout_ms / portTICK_PERIOD_MS; /* convert milliseconds to ticks */
 
TimeOut_t xTimeOut;
 
int recvLen = 0;
 
 
 
vTaskSetTimeOutState(&xTimeOut); /* Record the time at which this function was entered. */
 
do
 
{
 
        recvLen = n->netdev->Read(n->netdev, (char*)buffer, len, timeout_ms);
 
//        if(n->netdev->Read(n->netdev, (char*)buffer, len, timeout_ms) == 0) recvLen = len;
 
} while (recvLen < len && xTaskCheckForTimeOut(&xTimeOut, &xTicksToWait) == pdFALSE);
 
 
 
return recvLen;
 
}
 
 
 
int FreeRTOS_write(Network* n, unsigned char* buffer, int len, int timeout_ms)
 
{
 
// TickType_t xTicksToWait = timeout_ms / portTICK_PERIOD_MS; /* convert milliseconds to ticks */
 
// TimeOut_t xTimeOut;
 
int sentLen = 0;
 
 
 
// vTaskSetTimeOutState(&xTimeOut); /* Record the time at which this function was entered. */
 
// do
 
// {
 
        if(n->netdev->Write(n->netdev, (char*)buffer, len, timeout_ms) == 0) sentLen = len;
 
// } while (sentLen < len && xTaskCheckForTimeOut(&xTimeOut, &xTicksToWait) == pdFALSE);
 
 
 
return sentLen;
 
}

最后是断开连接，建立连接与初始化函数：

void FreeRTOS_disconnect(Network* n)
 
{
 
    TCP_UDP_Info tcp = {TCP_ID};
 
n->netdev->Disconnect(n->netdev, (char*)&tcp, 100);
 
}
 
 
 
void NetworkInit(Network* n)
 
{
 
    const static WiFiInfo wifi = {WiFi_ID, "ChinaNet-PVwx", "3nwspwfc"};
 
    n->netdev = NetDev_GetDev(ESP8266);
 
    if(n->netdev != NULL)
 
    {
 
        if(n->netdev->Init(n->netdev) == 0)
 
        {
 
            if(n->netdev->Connect(n->netdev, (char*)&wifi, 5000) == 0)
 
            {
 
                printf("Connect WiFi success.\r\n");
 
                n->mqttread = FreeRTOS_read;
 
                n->mqttwrite = FreeRTOS_write;
 
                n->disconnect = FreeRTOS_disconnect;
 
            }
 
            else
 
            {
 
                printf("Connect WiFi failed.\r\n");
 
            }
 
        }
 
        else
 
        {
 
            printf("Net Device Init failed.\r\n");
 
        }
 
    }
 
    else
 
    {
 
        printf("Net Device not found.\r\n");
 
    }
 
}
 
 
 
 
 
int NetworkConnect(Network* n, char* addr, int port)
 
{
 
    TCP_UDP_Info tcp = {TCP_ID, addr, 0, port};
 
    return n->netdev->Connect(n->netdev, (char*)&tcp, 500);
 
}

至此MQTT协议已经移植完成。

最后是关于MQTT数据连接对象的一些注意事项：

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