MQTT协议在STM32上的移植

MQTT协议在STM32上的移植

The Eclipse Paho project provides open-source client implementations of MQTT and MQTT-SN messaging protocols aimed at new, existing, and emerging applications for the Internet of Things (IoT).

开发平台

软件环境

• Keil uVision 5.12
• STM32F10x_StdPeriph_Lib_V3.5.0 标准库

硬件环境

• stm32f103系列
• SIM800C无线通讯GSM模块

参考文档

• MQTT协议中文版

下载MQTT 嵌入式C/C++库

本篇是MQTT在STM32设备上的移植，因此使用paho的嵌入式C库,源码地址https://github.com/eclipse/paho.mqtt.embedded-c.

移植

首先，需要将../paho.mqtt.embedded-c/MQTTPacket/中的所有文件添加到keil工程文件，然后参考../paho.mqtt.embedded-c/MQTTPacket/samples/中的例程编写。

移植的前提是保证已经建立TCP连接，因为MQTT协议实在TCP基础上的数据传输协议。本实验使用sim800c无线通讯模块先与MQTT服务器建立TCP连接（使用透传模式），再通过串口与stm32建立通讯联系。

接口函数

移植主要参考修改库中的../paho.mqtt.embedded-c/MQTTPacket/samples/transport.c例程文件
，且主要是transport_sendPacketBuffer()和transport_getdata()函数，分别用来作为硬件实现发送和接收数据包的接口函数，因此需要针对硬件平台做相应修改。

int32_t transport_sendPacketBuffer(uint8_t* buf, uint32_t buflen)
{
   int rc = 0;

   SendBuffer(UART4, buf, buflen);

   return rc;
}
int32_t transport_getdata(uint8_t* buf, int32_t count)
{
   int32_t n, rc = 0;

   memcpy(buf, (void*)&RxBuffer4[readBufLen], count);
   readBufLen += count;

   return count;
}

连接

uint8_t mqtt_connect(void)
{
   MQTTPacket_connectData data = MQTTPacket_connectData_initializer;
   int rc = 0;
   uint8_t buf[200];
   int buflen = sizeof(buf);
   int mysock = 0;
   MQTTString topicString = MQTTString_initializer;
   int len = 0;
   data.clientID.cstring = "yao";
   data.keepAliveInterval = 20;      //seconds
   data.cleansession = 1;
   data.username.cstring = "nncy";
   data.password.cstring = "nncy";
   data.MQTTVersion = 4;
   len = MQTTSerialize_connect((unsigned char *)buf, buflen, &data);
//    len += MQTTSerialize_disconnect((unsigned char *)(buf + len), buflen - len);
   rc = transport_sendPacketBuffer(buf, len);
   printf("len:%d|rc:%d\r\n", len, rc);

   reset_receive_buf();

   /* wait for connack */
   if (MQTTPacket_read(buf, buflen, transport_getdata) == CONNACK)
   {
       unsigned char sessionPresent, connack_rc;
       if (MQTTDeserialize_connack(&sessionPresent, &connack_rc, buf, buflen) != 1 || connack_rc != 0)
       {
           printf("Unable to connect, return code %d\n", connack_rc);
           return 0;
       }
       else
       {
           printf("MQTT CONNECT!\n");
       }
   }
   else
       printf("no connack\n");
       return 0;
}

订阅和发布函数

void mqtt_publish(char *pPubTopic, char *pMessage)
{
   MQTTPacket_connectData data = MQTTPacket_connectData_initializer;
   int rc = 0;
   uint8_t buf[200];
   int buflen = sizeof(buf);
   int mysock = 0;
   MQTTString topicString = MQTTString_initializer;
   char* payload = pMessage;
   int payloadlen = strlen(payload);
   int len = 0;
   topicString.cstring = pPubTopic;
   len += MQTTSerialize_publish((unsigned char *)(buf + len), buflen - len, 0, 0, 0, 0, topicString, (unsigned char *)payload, payloadlen);
//    len += MQTTSerialize_disconnect((unsigned char *)(buf + len), buflen - len);
   rc = transport_sendPacketBuffer(buf, len)
}
uint8_t mqtt_subscribe(char *pSubTopic)
{
   uint8_t buf[200] = {0};
   uint32_t buflen = sizeof(buf);
   int32_t msgid = 1;
   int32_t req_qos = 0;
   uint32_t rc, len = 0;
   MQTTString topicString = MQTTString_initializer;
   topicString.cstring = pSubTopic;

   len = MQTTSerialize_subscribe(buf, buflen, 0, msgid, 1, &topicString, &req_qos);
   rc = transport_sendPacketBuffer(buf, len);
   reset_receive_buf();
   if (MQTTPacket_read(buf, buflen, transport_getdata) == SUBACK) /* wait for suback */
   {
       unsigned short submsgid;
       int subcount;
       int granted_qos;
       rc = MQTTDeserialize_suback(&submsgid, 1, &subcount, &granted_qos, buf, buflen);
       if (granted_qos != 0)
       {
           printf("granted qos != 0, %d\n", granted_qos);
           return 0;
       }
       else
       {
           printf("granted qos = 0\n");
           return 1;
       }
   }
   else
       printf("no suback received!\r\n");
       return 0;
}

接收数据包解析函数

bool MQTT_Received_Data_Parser(char *Topic, char *message)
{
   uint8_t len = 0;
   uint8_t buf[256];

   len = uart4RxBufLen;
   printf("Received data lenth:%d\r\n", len);

   if (strstr(RxBuffer4, "CLOSED")){
       GPRS_CIP_MODE = 0;
       return false;
   } else {
       memcpy(buf, (void*)&RxBuffer4, len);

       printf("buf:%s\r\n", buf);
       printf("topicLength:%d\r\n", buf[3]);
       printf("Topic: %s\r\n", buf+4);
       printf("dataLength:%d\r\n", buf[1]-buf[3]-2);
       printf("Message: %s\r\n", buf+4+buf[3]);


       if (0xD0 == *buf) {
           printf("MQTT Heart Beat \r\n");
       } else {
           strncpy(Topic,(void*)(buf+4),buf[3]);
           printf("Topic: %s\r\n", Topic);
           strncpy(message,(void*)(buf+4+buf[3]),buf[1]-buf[3]-2);
           printf("Message: %s\r\n", message);

           memset(buf,0,sizeof(buf));
       }
   }
   return true;
}

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