I am struggling to get ESP8266 connected to an Arduino Uno working reliably as a webserver. The firmware of my ESP8266 is 1.1.1 - I don’t have the option (or knowledge) to update it at the moment. Below is my code. It works, barely, if I serve a small string. However, it usually closes the connection or just loads forever (crashes?) if I try to load the page from the browser three or four times. Ultimately I need to serve a webpage with json embedded in it that will load a second page served by the esp8266, a json file. I have a working demo of that but it crashes after a few retrievals. I understand that my html page is too long for strings so have been attempting to shift across to PROGMEM, initially testing with just a short string. I am storing and retrieving that correctly (I think, at least I can Serial.print it) but as soon as I try to write it to the ESP8266 I get a never ending load in my browser.
Where am I going wrong here? Is it the string/PROGMEM that is causing the issues or is there something else I’m missing in the AT commands (like some sort of ping to keep the connection open)?
//load softserial library
#include <SoftwareSerial.h>
#include <avr/pgmspace.h>
//set a boolean constant variable to true
//#define DEBUG true
const boolean DEBUG = true;
//RX (pin 2) goes to TX on esp8266, TX (pin 3) goes to RX on esp8266
SoftwareSerial esp8266(2, 3);
//input from the photoresistor
//int photoresistorpin = 0;
//create a PROGMEM variable
//String WEBPAGE = "hello";
static const char PROGMEM WEBPAGE[] = {"hello"};
/*
static const char WEBPAGE[] PROGMEM = R"rawliteral(
<html>
<head>
<meta name="viewport" content="width=device-width, minimumscale=1, maximum-scale=1, initial-scale=1">
</head>
<h1>Light:</h1><div id="light"></div>
<script>
function loadDoc()
{
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200)
{
var obj = JSON.parse(this.responseText);
document.getElementById('light').innerHTML = obj.data[0].datavalue;
}
};
xhttp.open('GET', 'data.json', true); xhttp.send();
}
var timedEvent = setInterval(function() { loadDoc(); }, 5000);
</script>
</body>
</html>
)rawliteral";
*/
//const int WEBPAGE_len = sizeof(WEBPAGE)/sizeof(WEBPAGE[0]);
void setup()
{
//open the serial port
Serial.begin(115200);
//print setup started in the serial monitor
Serial.println("Setup started");
//start esp8266 module (note: your esp's baud rate might be different)
esp8266.begin(115200);
//reset esp8266 module
senddata("AT+RST\r\n", 2000, DEBUG);
//set esp8266 as access point mode
//1 = Station mode (client)
//2 = Access point mode (host)
//3 = Access point mode + Station mode
senddata("AT+CWMODE=2\r\n", 1000, DEBUG);
//get ip address for esp8266
senddata("AT+CIFSR\r\n", 2000, DEBUG);
//configure esp8266 for multiple connections
senddata("AT+CIPMUX=1\r\n", 1000, DEBUG);
//turn on esp8266 server on port 80
senddata("AT+CIPSERVER=1,80\r\n", 1000, DEBUG);
//setup completed
Serial.println("Setup done");
}
void loop()
{
//take a reading from the photoresistor
//int lightval = analogRead(photoresistorpin);
int lightval = random(1000);
//to test
//Serial.println(lightval);
//is the esp8266 sending a message
if (esp8266.available())
{
//if received data from esp8266
if (esp8266.find("+IPD,"))
{
//subtract 48 because the read() function returns the ASCII decimal
//value and 0 (the first decimal number) starts at 48
int connectionid = esp8266.read() - 48;
//Serial.println("");
//Serial.println("*****");
//Serial.print("string = ");
//read the url sent by the client, look for the variable (/)
String msg;
esp8266.find("/");
delay(100);
msg = esp8266.readStringUntil(' ');
String pathrequested = msg.substring(0);
Serial.println("*****");
Serial.println(pathrequested);
Serial.println("*****");
//create a senddata string to send the webpage to the esp8266
String cipsend = "AT+CIPSEND=" + String(connectionid) + ",";
//cipsend += WEBPAGE.length();
cipsend += strlen_P(WEBPAGE);
cipsend += "\r\n";
Serial.println(cipsend);
char buffer[1000];
strcpy_P(buffer, WEBPAGE);
Serial.println(buffer);
//senddata(cipsend, 500, DEBUG);
//senddata(WEBPAGE, 500, DEBUG);
senddata(buffer, 500, DEBUG);
//create a string closecommand with the connection id and send it
String closecommand = "AT+CIPCLOSE=" + String(connectionid) + "\r\n";
senddata(closecommand, 500, DEBUG);
//increment the count
//count++;
}
}
}
void senddata(String command, const int timeout, boolean debug)
{
//send the received command to the esp8266
esp8266.print(command);
//set int variable to the number of millisends since Arduino began
long int time = millis();
//while the time and the timeout is less than the number of millisends since Arduino began
while((time + timeout) > millis())
{
//while the esp8266 is sending messages
while(esp8266.available())
{
//display output in the serial window
Serial.write(esp8266.read());
}
}
}