1.基础知识
sprintf()函数：将各种类型的数据构造成字符串类型。
int sprintf( char *buffer, const char *format [, argument] … );
除了前两个参数类型固定外，后面可以接任意多个参数。而它的精华，显然就在第二个参数：格式化字符串上。
1.格式化数字字符串
sprintf(s, "%d", 123); // 产生"123"
2.控制浮点数打印格式
1 2 3 sprintf(s, "%10.3f", 3.1415626); // 产生：" 3.142″ sprintf(s, "%-10.3f", 3.1415626); // 产生："3.142 " sprintf(s, "%.3f", 3.1415626); // 不指定总宽度，产生："3.142"
3.连接字符串
1 2 3 char *who = "I"; char *whom = "52PHP"; sprintf(s, "%s love %s.", who, whom); // 产生："I love 52PHP. "
4.打印地址信息
1 sprintf(s, "%p", &i);
5.返回值为字符串的长度
1 int len = sprintf(s, "%d", i);
strcpy()函数：将一个字符串复制到另一块空间地址中，‘\0’是停止拷贝的终止条件，同时也会将 '\0' 也复制到目标空间。
char* strcpy(char* destination,const char* source);
注意事项：源字符必须以‘\0’结束，目标空间必须足够大，以确保能放源字符串，目标空间必须可变。
2.ESP32通过MQTT上传温湿度数据至阿里云服务器
注意事项：上传的数据格式因为阿里云物模型上报规定需要加上params和method，还有上传的键值需要和设置的物模型的标识符一致。
eg:{"params":
{"Temp": %d ,
"Hum": %d ,
"Light": %d,
"Led":%d,
"Beep":%d},
"method": "thing.event.property.post"}
#include
#include
#include
#include
#include
#include
#define DHTPIN 2
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE);
// const char *ssid = "leisure";
// const char *password = "shadow27";
const char *ssid = "TP-LINK_9B47";
const char *password = "MengYun1006&";
const char *mqttServer = "iot-06z00formvsxwnm.mqtt.iothub.aliyuncs.com";
const char *mqttUserName = "device2&i3c6vjLss9C";
const char *mqttPwd = "27ae4ab21d99554afb9b02e224e1543eccdfa3400c378f01bdf43140ad5aae56";
const char *clientId = "i3c6vjLss9C.device2|securemode=2,signmethod=hmacsha256,timestamp=1672664951875|";
const char *subTopic = "/i3c6vjLss9C/device2/user/mytopic";
#define ALINK_BODY_FORMAT "{\"id\":\"device2\",\"version\":\"1.0\",\"method\":\"thing.event.property.post\",\"params\":%s}"
#define ALINK_TOPIC_PROP_POST "/sys/i3c6vjLss9C/device2/thing/event/property/post" // 发布主题
unsigned long lastMS = 0;
WiFiClient esp32Client;
PubSubClient mqttClient(esp32Client);
void connectwifi()
{
WiFi.mode(WIFI_STA);
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED)
{
vTaskDelay(500);
Serial.print(F("."));
}
Serial.println(F(""));
Serial.println(F("WiFi Connected!"));
Serial.println(F(""));
}
/*订阅主题*/
void subscribeTopic()
{
if (mqttClient.subscribe(subTopic))
{
Serial.print("Subscribed Topic: ");
Serial.println(subTopic);
}
else
{
Serial.print("Subscribe Fail...");
}
}
void connectMQTTServer()
{
while (!mqttClient.connected())
{
if (mqttClient.connect(clientId, mqttUserName, mqttPwd))
{
Serial.println(F("MQTT connected"));
subscribeTopic(); // 订阅指定主题
}
else
{
Serial.print("failed, rc=");
Serial.print(mqttClient.state());
Serial.println(" try again in 5 seconds");
vTaskDelay(5000);
}
}
}
/*subscribe call back*/
void receiveCallback(char *topic, byte *payload, unsigned int length)
{
Serial.print(F("Message arrived in topic: "));
Serial.println(topic);
Serial.print("Message:");
String data = "";
for (int i = 0; i < length; i++)
{
Serial.print((char)payload[i]);
data += (char)payload[i];
}
Serial.println("");
Serial.print("Message Length(Bytes) ");
Serial.println(length);
Serial.println();
Serial.println("-----------------------");
Serial.println(data);
/*JSON数据解析*/
StaticJsonDocument<32> doc;
DeserializationError error = deserializeJson(doc, data);
if (error)
{
Serial.print("deserializeJson() failed: ");
Serial.println(error.c_str());
return;
}
int msg = doc["msg"]; // 1
Serial.print("msg = ");
Serial.println(msg);
/*根据JSON信息执行相应的动作*/
switch (msg)
{
case 1:
Serial.println("LED_on");
break;
case 2:
Serial.println("LED_off");
break;
default:
break;
}
}
void pubMQTTmsg()
{
char param[32];
char jsonBuf[128];
float h = dht.readHumidity();
float t = dht.readTemperature();
sprintf(param, "{\"humi\":%2f}", h); // 换成对应的标识符
sprintf(jsonBuf, ALINK_BODY_FORMAT, param);
Serial.println(jsonBuf);
boolean b = mqttClient.publish(ALINK_TOPIC_PROP_POST, jsonBuf);
if (b)
{
Serial.println("publish Humidity success");
}
else
{
Serial.println("publish Humidity fail");
}
sprintf(param, "{\"temp\":%2f}", t); // 换成对应的标识符
sprintf(jsonBuf, ALINK_BODY_FORMAT, param);
Serial.println(jsonBuf);
boolean c = mqttClient.publish(ALINK_TOPIC_PROP_POST, jsonBuf);
if (c)
{
Serial.println("publish Humidity success");
}
else
{
Serial.println("publish Humidity fail");
}
}
void setup()
{
Serial.begin(115200);
connectwifi();
dht.begin();
mqttClient.setServer(mqttServer, 1883);
// mqttClient.setCallback(receiveCallback);
connectMQTTServer();
}
void loop()
{
if (!mqttClient.connected())
{
connectMQTTServer();
}
mqttClient.setCallback(receiveCallback);
if(millis()-lastMS>=1000){
lastMS = millis();
pubMQTTmsg();//上报信息
}
// 处理信息以及心跳
mqttClient.loop();
}
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