MQTT在嵌入式Linux上的點燈和關燈

MQTT運行

• 阿里雲創建設備
• MQTT源碼下載及編譯
• MQTT移植到ARM Linux平臺
• MQTT點燈和關燈

阿里雲創建設備

注意：我這裏用的是連接協議是WIFI協議，如果用網線連接的話，創建的時候選擇：“以太網”

MQTT源碼下載及編譯

• https://code.aliyun.com/edward.yangx/public-docs/wikis/user-guide/Linkkit_User_Manual
  • 在該網頁下有“快速體驗”連接，點擊後按照下述連接描述在Ubuntu上進行驗證
  • https://code.aliyun.com/edward.yangx/public-docs/wikis/user-guide/linkkit/Quick_Start
  • 可能是因爲我裝的18.04的版本，雖然已經按照指示安裝gawk了，但是還是提示相關的信息如下：
    
    *在設備上創建Topic，和mqtt_example.c中的對應起來
    

MQTT移植到ARM Linux平臺

• https://code.aliyun.com/edward.yangx/public-docs/wikis/user-guide/linkkit/Port_Guide/Build_Example
• make reconfig
  
• make 生成ARM在的mqtt_example可執行程序
  
  

MQTT點燈和關燈

創建一個LED設備後，以mqtt_example.c爲模板，這裏需要用到cjson

#include "cJSON.h"
...
void example_message_arrive(void *pcontext, void *pclient, iotx_mqtt_event_msg_pt msg)
{
    int fd;
	const char *leds = "/sys/class/leds/led-run/brightness";
	cJSON *json = NULL;
	cJSON *json_params = NULL;
	cJSON *json_id = NULL;
	cJSON *json_led = NULL;
    iotx_mqtt_topic_info_t     *topic_info = (iotx_mqtt_topic_info_pt) msg->msg;

    switch (msg->event_type) {
        case IOTX_MQTT_EVENT_PUBLISH_RECEIVED:
            /* print topic name and topic message */
            EXAMPLE_TRACE("Message Arrived:");
            EXAMPLE_TRACE("Topic  : %.*s", topic_info->topic_len, topic_info->ptopic);
            EXAMPLE_TRACE("Payload: %.*s", topic_info->payload_len, topic_info->payload);
            EXAMPLE_TRACE("\n");

            json = cJSON_Parse(topic_info->payload);
            if (!json)  
		    {  
			    HAL_Printf("Error before: [%s]\r\n",cJSON_GetErrorPtr());  
		    } 
            else
            {
                json_id = cJSON_GetObjectItem(json , "id");
                if(json_id->type == cJSON_String)
			    {
				    HAL_Printf("id:%s\r\n", json_id->valuestring);  
			    }
                json_params = cJSON_GetObjectItem(json , "params");
                if(json_params) 
                {
                   if(cJSON_GetObjectItem(json_params, "led"))
				    {
					json_led  = cJSON_GetObjectItem(json_params, "led");//get json data
					if(json_led->type == cJSON_Number)
					    {
						    HAL_Printf("LED:%d\r\n", json_led->valueint);  
						    if((fd = open(leds, O_RDWR|O_NOCTTY|O_NDELAY))<0)
                            {
                                HAL_Printf("open %s failed\n",leds);
                                perror("open leds");
                                exit(1);
                            }		
						    else
                            {			
							    if(json_led->valueint==1)
                                {
                                   write(fd,"1",1);     
                                }else{
                                   write(fd,"0",1);
                                }			
							    HAL_Printf("ioctl %s success, led %d\n",leds,json_led->valueint);		
						    }	
						close(fd);
					    }
				    } 
                }
            }
            cJSON_Delete(json);
            break;
        default:
            break;
    }
}
//消息訂閱
int example_subscribe(void *handle)
{
    int res = 0;
    const char *fmt = "/sys/%s/%s/thing/service/property/set";
    char *topic = NULL;
    int topic_len = 0;

    topic_len = strlen(fmt) + strlen(DEMO_PRODUCT_KEY) + strlen(DEMO_DEVICE_NAME) + 1;
    topic = HAL_Malloc(topic_len);
    if (topic == NULL) {
        EXAMPLE_TRACE("memory not enough");
        return -1;
    }
    memset(topic, 0, topic_len);
    HAL_Snprintf(topic, topic_len, fmt, DEMO_PRODUCT_KEY, DEMO_DEVICE_NAME);
	//IOT_MQTT_Subscribe向雲端訂閱指定的Topic
    res = IOT_MQTT_Subscribe(handle, topic, IOTX_MQTT_QOS0, example_message_arrive, NULL);
    if (res < 0) {
        EXAMPLE_TRACE("subscribe failed");
        HAL_Free(topic);
        return -1;
    }

    HAL_Free(topic);
    return 0;
}

• MQTT 相關API：https://code.aliyun.com/edward.yangx/public-docs/wikis/user-guide/linkkit/Prog_Guide/API/MQTT_Provides

完成以上內容參考了阿里提供的官方指導和橙子MAX發佈的視頻教程：https://www.bilibili.com/video/av55613036?from=search&seid=4167138359701025330