MQTT在嵌入式Linux上的点灯和关灯

本文主要是介绍MQTT在嵌入式Linux上的点灯和关灯，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

MQTT运行

阿里云创建设备
MQTT源码下载及编译
MQTT移植到ARM Linux平台
MQTT点灯和关灯

阿里云创建设备

注意：我这里用的是连接协议是WIFI协议，如果用网线连接的话，创建的时候选择：“以太网”
在这里插入图片描述

MQTT源码下载及编译

https://code.aliyun.com/edward.yangx/public-docs/wikis/user-guide/Linkkit_User_Manual
- 在该网页下有“快速体验”连接，点击后按照下述连接描述在Ubuntu上进行验证
- https://code.aliyun.com/edward.yangx/public-docs/wikis/user-guide/linkkit/Quick_Start
- 可能是因为我装的18.04的版本，虽然已经按照指示安装gawk了，但是还是提示相关的信息如下：
  
  *在设备上创建Topic，和mqtt_example.c中的对应起来

MQTT移植到ARM Linux平台

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可执行程序

MQTT点灯和关灯

创建一个LED设备后，以mqtt_example.c为模板，这里需要用到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 dataif(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;}
}
//消息订阅
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向云端订阅指定的Topicres = 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;
}