今天非常榮幸向各位小伙伴詳細(xì)展示一個由共創(chuàng)社成員完成的MQTT遠(yuǎn)程溫濕度監(jiān)控系統(tǒng)項(xiàng)目。該項(xiàng)目借助ELF 1開發(fā)板作為核心技術(shù)支撐，成功實(shí)現(xiàn)了對各類環(huán)境空間中溫濕度數(shù)據(jù)的實(shí)時、遠(yuǎn)程、穩(wěn)定監(jiān)測。該系統(tǒng)不僅集成了先進(jìn)的數(shù)據(jù)采集模塊，用于精確感知現(xiàn)場環(huán)境變化，同時利用MQTT協(xié)議的輕量級特性，確保了數(shù)據(jù)在復(fù)雜網(wǎng)絡(luò)環(huán)境下的可靠傳輸。在此接下來，就為各位小伙伴詳盡展示這一項(xiàng)目的相關(guān)細(xì)節(jié)。

1、Linux開發(fā)板開發(fā)環(huán)境搭建

（1）開發(fā)板動態(tài)分配ip地址

（開發(fā)板與家用路由器連接，路由器支持DHCP自動IP地址分配）

root@ELF1:~# udhcpc -i eth0

（2）將nfs服務(wù)器掛載到開發(fā)板的/mnt目錄

（其中“192.168.1.10”是Ubuntu的ens36的ip）

root@ELF1:~# mount -t nfs -o nolock,vers=3 192.168.1.10:/home/book/nfs_rootfs /mnt

可以看到開發(fā)板的/mnt目錄已經(jīng)有了文件。

2、Ubuntu編譯環(huán)境搭建：

（1）將paho mqtt的官方庫克隆到Ubuntu的“~/nfs_rootfs”路徑

book@100ask:~/nfs_rootfs$ git clone https://github.com/eclipse/paho.mqtt.c.git

（2）修改“~/nfs_rootfs/paho_mqtt/paho.mqtt.c”路徑下的Makefile文件

修改prefix所代表的工具鏈路徑：

修改編譯器：

（3）編譯后得到鏈接庫

book@100ask:~/nfs_rootfs/paho_mqtt/paho.mqtt.c$ make

arm-gcc編譯生成的.so庫文件，保存在paho.mqtt.c/build/output里面。

將.so庫文件安裝到本地PC：

book@100ask:~/nfs_rootfs/paho_mqtt/paho.mqtt.c$ sudo make install

（4）將.so庫文件安裝到開發(fā)板的“/lib”路徑，開發(fā)板才能運(yùn)行paho mqtt編譯后的可執(zhí)行文件

root@ELF1:~# install /mnt/paho_mqtt/paho.mqtt.c/build/output/libpaho-mqtt3* /lib

以上開發(fā)環(huán)境搭建完成！

3、工程文件的建立

（1）將“~/nfs_rootfs/paho_mqtt/paho.mqtt.c”

路徑中的src文件夾拷貝到“~/nfs_rootfs/mqtt_iot”路徑下

book@100ask:~$ cp -r ~/nfs_rootfs/paho_mqtt/paho.mqtt.c ~/nfs_rootfs/mqtt_iot

（2）在“~/nfs_rootfs/mqtt_iot”路徑下添加文件：

4、阿里云服務(wù)器設(shè)置：

（1）服務(wù)器的注冊及產(chǎn)品、設(shè)備設(shè)置可以參照ElfBoard官方文檔：《01-1 ELF1、ELF1S開發(fā)板_軟件教程_V1》第5章-5.4小節(jié)。

（2）工程文件中所需要的服務(wù)器參數(shù)查找

查看服務(wù)器地址

查看DeviceName、DeviceSecret

查看MQTT連接參數(shù)

5.工程文件的編譯執(zhí)行

（1）編譯工程文件，得到可在Linux開發(fā)板上執(zhí)行的Main二進(jìn)制文件

book@100ask:~/nfs_rootfs/mqtt_iot$ arm-buildroot-linux-gnueabihf-gcc main.c mqtt_iot.c -o main -lpaho-mqtt3c -lpthread

MQTT的異步通信收發(fā)，依賴的庫是libpaho-mqtt3a，MQTT的同步通信收發(fā)，依賴的庫就是libpaho-mqtt3c。此外工程編譯的時候需要鏈接線程的庫pthread，所以編譯的時候要加上-lpthread。

（2）開發(fā)板運(yùn)行程序

root@ELF1:/mnt/mqtt_iot# ./main

（3）實(shí)驗(yàn)結(jié)果

Linux開發(fā)板將采集到的溫度、濕度數(shù)據(jù)每5s上傳一次阿里服務(wù)器，串口窗口顯示數(shù)據(jù)發(fā)送成功字符。此外通過阿里服務(wù)器日志服務(wù)可以看到濕度、溫度數(shù)據(jù)。

通過阿里服務(wù)器調(diào)試窗口給開發(fā)板發(fā)送LED1、LED2控制指令。

6、下面將貼出工程文件的代碼，并介紹其思路

（1）main.c文件

//main.c //定義線程句柄 pthread_t discon_t; pthread_t thread_AT20Read_t; pthread_t thread_ledctrl_t; static int isConnected = 0;//表明客戶端和服務(wù)器是斷開還是連接狀態(tài)(1-連接狀態(tài),-1斷開狀態(tài)) static void *thread_AT20Read(void *paramater) { int fd = -1; unsigned int databuf[2]; int c1,t1; float hum,temp; int ret = 0; msgbuf pubMsg = {2, 0}; while(fd < 0){ fd = open(AHT20_DEV, O_RDWR); if(fd < 0){ printf("can't open file %s\r\n", AHT20_DEV); sleep(1); }else{ printf("open file %s successfully\r\n", AHT20_DEV); } } while(1){ ret = read(fd, databuf, sizeof(databuf)); if(ret == 0){ c1 = databuf[0]*1000/1024/1024; t1 = databuf[1] *200*10/1024/1024-500; hum = (float)c1/10.0; temp = (float)t1/10.0; //printf("hum = %0.2f temp = %0.2f \r\n",hum,temp); pubMsg.mtext[0] = (unsigned int)(hum*100); pubMsg.mtext[1] = (unsigned int)(temp*100); int ret1 = msgsnd(pubmsg_d, &pubMsg.mtype, sizeof(pubMsg.mtext), IPC_NOWAIT); // 非阻塞發(fā)送 if(ret1 != 0) { printf("Failed to send message.\r\n"); } } sleep(5); } } static void *thread_ledctrl(void *paramater) { int on=1; int led; int fd; msgbuf subMsg = {1, 0}; fd = open(LED_BRIGHTNESS, O_WRONLY); if(fd < 0) { perror("open device leds"); exit(1); } system(LED1_OFF); system(LED2_OFF); while(1) { int res = msgrcv(submsg_d, &subMsg, sizeof(subMsg.mtext), 0, 0);//阻塞 if(res < 0) continue; else{ if((subMsg.mtext[0] & 0x01)== 1){ system(LED1_ON); }else{ system(LED1_OFF); } if((subMsg.mtext[0] & 0x02)== 0x02){ system(LED2_ON); }else{ system(LED2_OFF); } } } } //斷開和mqtt服務(wù)器連接的線程入口函數(shù) static void *mqtt_disconnect_t(void* argv) { int retval; while(1) { char ch; ch = getchar(); if(ch=='Q' || ch=='q') { printf("Try to exit mqtt task\n"); if(mqtt_disconnect() == EXIT_SUCCESS) break; } } isConnected = -1; pthread_exit(&retval); // 退出線程 return NULL; } int main(void) { //初始化mqtt成功建立客戶端和服務(wù)器的連接后，將主動斷開服務(wù)器的任務(wù)放到一個線程里面去 //成功建立客戶端和服務(wù)器的連接且訂閱主題后才創(chuàng)建斷開連接的線程 if(mqtt_iot() == 0) { isConnected = 1; pthread_create(&discon_t, 0, mqtt_disconnect_t, NULL); } //AT20 read thread int ret = pthread_create(&thread_AT20Read_t, NULL, thread_AT20Read, NULL); if(ret != 0) { printf("Failed to create AT20Read thread.\n"); return -1; } //led control thread ret = pthread_create(&thread_ledctrl_t, NULL, thread_ledctrl, NULL); if(ret != 0) { printf("Failed to create ledctrl thread.\n"); return -1; } while(1) { //printf("isConnected state:%d\n",isConnected); sleep(5); } return 0; }

（2）mqtt_iot.c文件

//mqtt_iot.c volatile MQTTClient_deliveryToken deliveredtoken; pthread_t threads[2]; sem_t discon_sem;//信號量 int pubmsg_d = -1; int submsg_d = -1; msgbuf subMsg = {1, 0}; msgbuf pubMsg = {2, 0}; pthread_t thread_mqtt_publish_t; MQTTClient client; //定義一個MQTT客戶端client MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer; //傳遞給MQTTClient_setCallbacks的回調(diào)函數(shù)，消息發(fā)送成功后，調(diào)用此回調(diào)函數(shù) void delivered(void *context, MQTTClient_deliveryToken dt) { printf("Message with token value %d delivery confirmed\n", dt); deliveredtoken = dt; } //傳遞給MQTT-Client_setCallbacks的回調(diào)函數(shù) 消息到達(dá)后，調(diào)用此回調(diào)函數(shù) int msgarrvd(void *context, char *topicName, int topicLen, MQTTClient_message *message) { printf("---------------------------------------------------------------\n"); printf("Message arrived\n"); printf(" topic: %s\n", topicName); printf(" message: %.*s\n", message->payloadlen, (char*)message->payload); printf("---------------------------------------------------------------\n"); subMsg.mtext[0] = 0; unsigned short len = message->payloadlen; char *buf = (char*)message->payload; for(unsigned short i=0; i='0') subMsg.mtext[0] = subMsg.mtext[0]*10 + buf[i] - '0'; } int ret = msgsnd(submsg_d, &subMsg.mtype, sizeof(subMsg.mtext), IPC_NOWAIT); // 非阻塞發(fā)送 if(ret != 0) { printf("Failed to send message.\r\n"); } MQTTClient_freeMessage(&message); // 釋放消息 MQTTClient_free(topicName); // 釋放主題名 return 1; } //傳遞給MQTTClient_setCallbacks的回調(diào)函數(shù) 連接異常斷開后調(diào)用此回調(diào)函數(shù) void connlost(void *context, char *cause) { printf("\nConnection lost\n"); printf(" cause: %s\n", cause); } //實(shí)現(xiàn)MQTT的發(fā)布 void *mqtt_publish(void *argv) { MQTTClient_message pubmsg = MQTTClient_message_initializer; MQTTClient_deliveryToken token; char data[9]; int rc; pubmsg.qos = QOS; pubmsg.retained = 0; while(1) { //接收消息(消息隊(duì)列的ID,存放消息的指針,指定接收消息的大小,0-讀取消息隊(duì)列中第一個數(shù)據(jù),阻塞) int res = msgrcv(pubmsg_d, &pubMsg, sizeof(pubMsg.mtext), 0, 0); if(res < 0) continue; { //printf("Publish_hum: %d\n", pubMsg.mtext[0]); //printf("Publish_temp: %d\n", pubMsg.mtext[1]); sprintf(data, "%d,%d", pubMsg.mtext[0],pubMsg.mtext[1]); pubmsg.payload = data; pubmsg.payloadlen = sizeof(data); if((rc = MQTTClient_publishMessage(client, PUB_TOPIC, &pubmsg, &token)) != MQTTCLIENT_SUCCESS) { printf("Failed to publish message, return code %d\n", rc); break; } rc = MQTTClient_waitForCompletion(client, token, TIMEOUT); printf("Message with delivery token %d delivered\n", token); } } if((rc = MQTTClient_disconnect(client, 10000)) != MQTTCLIENT_SUCCESS) //斷開和服務(wù)器的連接 { printf("Failed to disconnect, return code %d\n", rc); } pthread_exit(&threads[PubThread]); return NULL; } //封裝主動斷開連接服務(wù)器的函數(shù) int mqtt_disconnect(void) { int rc = EXIT_SUCCESS; //兩個參數(shù):MQTT客戶端和斷開連接超時時間 if ((rc = MQTTClient_disconnect(client, 10000)) != MQTTCLIENT_SUCCESS) //斷開和服務(wù)器的連接 { printf("Failed to disconnect, return code %d\n", rc); rc = EXIT_FAILURE; } else { printf("MQTT disconnect success\n"); MQTTClient_destroy(&client); } return rc; } // mqtt建立客戶端、連接服務(wù)器、訂閱主題的封裝入口函數(shù) int mqtt_iot(void) { int rc = EXIT_SUCCESS; //創(chuàng)建客戶端 if ((rc = MQTTClient_create(&client, ADDRESS, CLIENTID, MQTTCLIENT_PERSISTENCE_NONE, NULL)) != MQTTCLIENT_SUCCESS) { printf("Failed to create client, return code %d\n", rc); goto exit; } //設(shè)置回調(diào)函數(shù)(連接丟失處理回調(diào)函數(shù),處理訂閱消息的回調(diào)函數(shù),成功發(fā)布消息后的回調(diào)函數(shù)) if((rc = MQTTClient_setCallbacks(client, NULL, connlost, msgarrvd, delivered)) != MQTTCLIENT_SUCCESS) { printf("Failed to set callbacks, return code %d\n", rc); goto destroy_exit; } conn_opts.username = USERNAME; conn_opts.password = PASSWORD; conn_opts.keepAliveInterval = 60;//保活周期，客戶端向服務(wù)器發(fā)送心跳包的周期，單位秒 conn_opts.cleansession = 1; //連接服務(wù)器 if((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS) { printf("Failed to connect, return code %d\n", rc); goto destroy_exit; } //訂閱主題(傳入客戶端句柄、訂閱的主題以及消息質(zhì)量) if ((rc = MQTTClient_subscribe(client, SUB_TOPIC, QOS)) != MQTTCLIENT_SUCCESS) { printf("Failed to subscribe, return code %d\n", rc); goto destroy_exit; } //初始化信號量 if(sem_init(&discon_sem, 1, 0) != 0) { printf("Failed to init semaphore\n"); return -1; } //創(chuàng)建隊(duì)列 pubmsg_d = msgget(0x1234, IPC_CREAT); submsg_d = msgget(0x5678, IPC_CREAT); if(pubmsg_d == -1 || submsg_d==-1) //返回錯誤碼-1 { printf("Failed to create a mqtt message, pubid:%d, subid:%d\n", pubmsg_d, submsg_d); return -1; } else { printf("Publish message id: %d\n", pubmsg_d); printf("Subscribe message id: %d\n", submsg_d); } int ret = pthread_create(&thread_mqtt_publish_t, NULL, mqtt_publish, NULL); if(ret != 0) { printf("Failed to create mqtt_publish thread.\n"); return -1; } printf("MQTT connect success, press 'Q' or 'q' to disconnect mqtt server\n"); return 0; destroy_exit: MQTTClient_destroy(&client); //釋放客戶端的資源, 參數(shù)-同步客戶端的句柄 return -1; exit: return -1; }

至此，就完成了關(guān)于ELF 1開發(fā)板研發(fā)的MQTT遠(yuǎn)程溫濕度監(jiān)測系統(tǒng)介紹。希望這套實(shí)踐案例能夠成為各位小伙伴的寶貴參考，啟迪創(chuàng)新思維，推進(jìn)各位嵌入式愛好者在學(xué)習(xí)的道路上不斷前進(jìn)。