ESP8266 Community Forum

Posted: **Thu Feb 12, 2015 6:18 am**

Hey guys,

I've been stuck on getting the ESP8266 do a simple GET request on an Arduino Mega. I've tried both with serial using AT Commands and using Arduino Serial with the below code. I have the latest firmware installed (.95) and am getting the headers to work via telnet. Unfortunately I just don't get it to work with the ESP8266 - I've literally spent hours following examples but no luck yet.

It seems to me like the ESP8266 does not recognise \r\n\r\n at the end of the header where it stops it from transmitting. I've tried similar commands using serial with straight AT commands but also there it doesn't seem to allow me to get the Header straight as it continues to give me 400 errors.

If anyone can help me out or can point me in the right direction that would be just awesome!

Arduino Code

Code: Select all

#define SSID        "SSID"
#define PASS        "PASS"
#define DEST_HOST   "www.ntu.edu.sg"
#define TIMEOUT     10000 // mS
#define CONTINUE    false
#define HALT        true
#define ECHO_COMMANDS // Un-comment to echo AT+ commands to serial monitor

// Print error message and loop stop.
void errorHalt(String msg)
{
  Serial.println(msg);
  Serial.println("HALT");
  while(true){};
}

// Read characters from WiFi module and echo to serial until keyword occurs or timeout.
boolean echoFind(String keyword)
{
  byte current_char   = 0;
  byte keyword_length = keyword.length();
  
  // Fail if the target string has not been sent by deadline.
  long deadline = millis() + TIMEOUT;
  while(millis() < deadline)
  {
    if (Serial1.available())
    {
      char ch = Serial1.read();
      Serial.write(ch);
      if (ch == keyword[current_char])
        if (++current_char == keyword_length)
        {
          Serial.println();
          return true;
        }
    }
  }
  return false;  // Timed out
}

// Read and echo all available module output.
// (Used when we're indifferent to "OK" vs. "no change" responses or to get around firmware bugs.)
void echoFlush()
  {while(Serial1.available()) Serial.write(Serial1.read());}
  
// Echo module output until 3 newlines encountered.
// (Used when we're indifferent to "OK" vs. "no change" responses.)
void echoSkip()
{
  echoFind("\n");        // Search for nl at end of command echo
  echoFind("\n");        // Search for 2nd nl at end of response.
  echoFind("\n");        // Search for 3rd nl at end of blank line.
}

// Send a command to the module and wait for acknowledgement string
// (or flush module output if no ack specified).
// Echoes all data received to the serial monitor.
boolean echoCommand(String cmd, String ack, boolean halt_on_fail)
{
  Serial1.println(cmd);
  #ifdef ECHO_COMMANDS
    Serial.print("--"); Serial.println(cmd);
  #endif
  
  // If no ack response specified, skip all available module output.
  if (ack == "")
    echoSkip();
  else
    // Otherwise wait for ack.
    if (!echoFind(ack))          // timed out waiting for ack string 
      if (halt_on_fail)
        errorHalt(cmd+" failed");// Critical failure halt.
      else
        return false;            // Let the caller handle it.
  return true;                   // ack blank or ack found
}

// Connect to the specified wireless network.
boolean connectWiFi()
{
  String cmd = "AT+CWJAP=\""; cmd += SSID; cmd += "\",\""; cmd += PASS; cmd += "\"";
  if (echoCommand(cmd, "OK", CONTINUE)) // Join Access Point
  {
    Serial.println("Connected to WiFi.");
    return true;
  }
  else
  {
    Serial.println("Connection to WiFi failed.");
    return false;
  }
}
// ******** SETUP ********
void setup()  
{
  Serial.begin(115200);         // Communication with PC monitor via USB
  Serial1.begin(115200);        // Communication with ESP8266 via 5V/3.3V level shifter
  
  Serial1.setTimeout(TIMEOUT);
  Serial.println("ESP8266 Demo");
  
  delay(2000);
  echoCommand("AT+RST", "ready", HALT);    // Reset & test if the module is ready  
  Serial.println("Module is ready.");
  echoCommand("AT+GMR", "OK", CONTINUE);   // Retrieves the firmware ID (version number) of the module. 
  echoCommand("AT+CWMODE?","OK", CONTINUE);// Get module access mode. 
    
  echoCommand("AT+CWMODE=1", "", HALT);    // Station mode
  
  //connect to the wifi
  boolean connection_established = false;
  for(int i=0;i<5;i++)
  {
    if(connectWiFi())
    {
      connection_established = true;
      break;
    }
  }
  if (!connection_established) errorHalt("Connection failed");
  
  delay(2000);
  //echoCommand("AT+CWSAP=?", "OK", CONTINUE); // Test connection
  echoCommand("AT+CIFSR", "", HALT);         // Echo IP address. (Firmware bug - should return "OK".)
  //echoCommand("AT+CIPMUX=0", "", HALT);      // Set single connection mode
  delay(2000);
}


// ******** LOOP ********
void loop() 
{
  // Establish TCP connection
  String cmd = "AT+CIPSTART=\"TCP\",\""; cmd += DEST_HOST; cmd += "\",80";
  if (!echoCommand(cmd, "OK", CONTINUE)) return;
  delay(2000);
  
  // Get connection status 
  if (!echoCommand("AT+CIPSTATUS", "OK", CONTINUE)) return;
  // Build HTTP request.
  cmd = "GET / HTTP/1.0\r\n\r\n";
  String cipstart = "AT+CIPSEND=";
  cipstart += cmd.length();
  delay(5000);

  if (!echoCommand(cipstart, ">", CONTINUE))
  {
    echoCommand("AT+CIPCLOSE", "", CONTINUE);
    Serial.println("Connection timeout.");
    return;
  }
  delay(500);
  
  // Send the raw HTTP request
  echoCommand(cmd, "OK", CONTINUE);  // GET
  
  // Loop forever echoing data received from destination server.
  while(true)
    while (Serial1.available())
      Serial.write(Serial1.read());
      
  errorHalt("ONCE ONLY");
}

Response & Debug

Code: Select all

ESP8266 Demo
--AT+RST
AT+RST

OK

ets Jan  8 2013,rst cause:4, boot mode:(3,6)

wdt reset
load 0x40100000, len 612, room 16 
tail 4
chksum 0x12
load 0x3ffe8000, len 788, room 4 
tail 0
chksum 0x50
load 0x3ffe8314, len 264, room 8 
tail 0
chksum 0x4a
csum 0x4a

2nd boot version : 1.1
  SPI Speed      : 40MHz
  SPI Mode       : QIO
  SPI Flash Size : 4Mbit
jump to run user1

rlS

Vendor:www.ai-thinker.com

SDK Version:0.9.5(b1)
Compiled @:Dec 25 2014, 21:50:58
ready
Module is ready.
--AT+GMR

AT+GMR
00200.9.5(b1)
compiled @ Dec 25 2014 21:40:28
AI-THINKER Dec 25 2014

OK
--AT+CWMODE?

AT+CWMODE?
+CWMODE:1

OK
--AT+CWMODE=1


AT+CWMODE=1



--AT+CWJAP="stroopwafel","0403770414"
OK
Connected to WiFi.
--AT+CIFSR


AT+CWJAP="stroopwafel","0403770414"

AT+CIFSR


--AT+CIPSTART="TCP","www.ntu.edu.sg",80
AT+CIPSTART="TCP","www.ntu.edu.sg",80
CONNECT

OK
--AT+CIPSTATUS

AT+CIPSTATUS
STATUS:3
+CIPSTATUS:0,"TCP","155.69.6.173",80,0

OK
--AT+CIPSEND=18

AT+CIPSEND=18
>
--GET / HTTP/1.0


 GET / HTTP/1.0CLOSED

ERROR

Posted: **Sun Feb 15, 2015 11:40 pm**

I'm having a similar problem. No matter how I form the GET, I still get CLOSED as the response. I have tested the GET using hurl.it and it works fine. If I substitute http://www.google.com for the URL however it seems to work.
My version:
AT+GMR
00200.9.5(b1)
compiled @ Dec 25 2014 21:40:28
AI-THINKER Dec 25 2014

Posted: **Tue Feb 17, 2015 9:02 am**

Hey Pat,

While I haven't figured out how to fix the problem per se, I did find a workaround and am using CIPMODE=1. CIPSEND will not need the number of characters this way and will send everything to the server.

In my case this is fine but definitely not the clean approach I'm (still) looking for. You can exit the CIPSEND > mode by sending "+++" (whole string at once, otherwise it doesn't work).

Let me know if this works for you.

Posted: **Tue Feb 17, 2015 9:36 am**

I could never get GET requests to work with the AT command firmware. I've since moved to the NodeMCU firmware and using LUA is a delight. IMO, nobody should use the AT command firmware.

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