远程控制led实验中 returnValue 的中用
这是远程控制led灯的实验，在读代码的时对这句不怎么理解" String returnValue = "" ",跟后面这段代码if (client.available()) {
char c = client.read();
Serial.print(c);
if (c == '{')
ResponseBegin = true;
else if (c == '}')
ResponseBegin = false;
if (ResponseBegin)
returnValue += c;
}
if (returnValue.length() !=0 && (ResponseBegin == false))
{
Serial.println(returnValue);
if (returnValue.charAt(returnValue.length() - 1) == '1') {
Serial.println("turn on the LED");
digitalWrite(5, HIGH);
}
else if(returnValue.charAt(returnValue.length() - 1) == '0') {
Serial.println("turn off the LED");
digitalWrite(5, LOW);
}
returnValue = "";
的思路不怎么理解， returnValue 这个值有几次变更，其中有什么意义也不是很清楚，希望给我前辈多多指教。
/*
Yeelink sensor client power switch example
*/
#include <SPI.h>
#include <Ethernet.h>
#include <Wire.h>
#include <math.h>
byte buff;
/* for yeelink api, the initialze of the Yeelink including apikey ,device num ,sensor num,
serv num, local MAC .Yeelink ip.the time of the tow mesamges */
#define APIKEY "c142a1e19dec73dd5dde48309ad20590" // 此处替换为你自己的API KEY
#define DEVICEID 19112 // 此处替换为你的设备编号
#define SENSORID1 33270 // 此处替换为你的传感器编号
// assign a MAC address for the ethernet controller.
byte mac[] = { 0x00, 0x1D, 0x72, 0x82, 0x35, 0x9D};
// initialize the library instance:
EthernetClient client ;
char server[] = "api.yeelink.net"; // name address for yeelink API
unsigned long lastConnectionTime = 0; // last time you connected to the server, in milliseconds
boolean lastConnected = false; // state of the connection last time through the main loop
const unsigned long postingInterval = 3*1000; // delay between 2 datapoints, 30s
String returnValue = "";
boolean ResponseBegin = false;
void setup() {
pinMode(5, OUTPUT);
Wire.begin();
// start serial port:
Serial.begin(57600);
// start the Ethernet connection with DHCP:
if (Ethernet.begin(mac) == 0) {
Serial.println("Failed to configure Ethernet using DHCP");
for(;;)
;
}
else {
Serial.println("Ethernet configuration OK");
}
}
void loop() {
// if there's incoming data from the net connection.
// send it out the serial port.This is for debugging
// purposes only:
if (client.available()) {
char c = client.read();
Serial.print(c);
if (c == '{')
ResponseBegin = true;
else if (c == '}')
ResponseBegin = false;
if (ResponseBegin)
returnValue += c;
}
if (returnValue.length() !=0 && (ResponseBegin == false))
{
Serial.println(returnValue);
if (returnValue.charAt(returnValue.length() - 1) == '1') {
Serial.println("turn on the LED");
digitalWrite(5, HIGH);
}
else if(returnValue.charAt(returnValue.length() - 1) == '0') {
Serial.println("turn off the LED");
digitalWrite(5, LOW);
}
returnValue = "";
}
// if there's no net connection, but there was one last time
// through the loop, then stop the client:
if (!client.connected() && lastConnected) {
Serial.println();
Serial.println("disconnecting.");
client.stop();
}
// if you're not connected, and ten seconds have passed since
// your last connection, then connect again and send data:
if(!client.connected() && (millis() - lastConnectionTime > postingInterval)) {
// read sensor data, replace with your code
//int sensorReading = readLightSensor();
Serial.print("yeelink:");
//get data from server
getData();
}
// store the state of the connection for next time through
// the loop:
lastConnected = client.connected();
}
// this method makes a HTTP connection to the server and get data back
void getData(void) {
// if there's a successful connection:
if (client.connect(server, 80)) {
Serial.println("connecting...");
// send the HTTP GET request:
client.print("GET /v1.0/device/");
client.print(DEVICEID);
client.print("/sensor/");
client.print(SENSORID1);
client.print("/datapoints");
client.println(" HTTP/1.1");
client.println("Host: api.yeelink.net");
client.print("Accept: *");
client.print("/");
client.println("*");
client.print("U-ApiKey: ");
client.println(APIKEY);
client.println("Content-Length: 0");
client.println("Connection: close");
client.println();
Serial.println("print get done.");
}
else {
// if you couldn't make a connection:
Serial.println("connection failed");
Serial.println();
Serial.println("disconnecting.");
client.stop();
}
// note the time that the connection was made or attempted:
lastConnectionTime = millis();
}
这个就是赋一个空值给 returnValue .
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