I have connected an ESP8266-01 module to an Arduino as in the following schematic with the RX and TX pins changed to pins 8 and 9 instead of 0 and 1:

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I am using the ESP8266wifi library at the following link:


I have looked at the ESP8266HTTPClient library but that is for the ESP8266 board. I want my code to run on the Arduino Uno and not on the ESP8266! I have written the following code:

#include <SoftwareSerial.h>
#include <SerialESP8266wifi.h>

const String API_PASSWORD = "stn1234";

#define RX_PIN          8   // RX of Arduino (connected to TX of ESP8266)
#define TX_PIN          9   // TX of Arduino (connected to RX of ESP8266)
#define ESP_RESET_PIN   12 

#define SERVER_IP           ""
#define SERVER_PORT         "80"
#define WIFI_SSID           "MyWIFI"
#define WIFI_PASSWORD       "myWifiPassword"

uint8_t wifi_started = false;

const char RST[] PROGMEM = "RST";
const char IDN[] PROGMEM = "*IDN?";

#define CHANGE_DELAY        5000

void initializeWifi();
void transmitData(String);
String getResponse();
void transmitStatus();

SoftwareSerial swSerial =  SoftwareSerial(RX_PIN, TX_PIN);
SerialESP8266wifi wifi(swSerial, swSerial, ESP_RESET_PIN, Serial);

void setup() 
    Serial.println("Initialization complete");

void loop() 
    Serial.print("Transmission complete, ");
    int s = (CHANGE_DELAY/1000);
    Serial.println("s until next cycle");

void transmitStatus()
    int a = (int)random(100);
    int b = (int)random(100);
    String url = "/LocalWebProject/api/testConnection.php?a=" + String(a) + "&b=" + String(b);

    String response = getResponse();
    Serial.print("Reply received: ");

void initializeWifi()
    Serial.println("Starting Wifi");
    wifi.endSendWithNewline(false);     // Will end all transmissions with a newline and carrage return ie println.. default is true

    wifi_started = wifi.begin();
        Serial.println("Wifi started, connecting to AP...");
        wifi.connectToAP(WIFI_SSID, WIFI_PASSWORD);
        Serial.println("Connected to AP");
    } else {
        Serial.println("ESP module not working");

void transmitData(String url)
    Serial.println("Connecting to server...");
    wifi.connectToServer(SERVER_IP, SERVER_PORT);

    String data = String("GET ") + url + " HTTP/1.1\r\n" +
           "Host: " + wifi.getIP() + "\r\n" + 
           "Connection: close\r\n\r\n";

    Serial.println("Connected. Transmitting data...");
    wifi.send(SERVER, data);

String getResponse()
        Serial.println("Waiting for response...");
        WifiMessage in = wifi.listenForIncomingMessage(6000);
            if(in.channel == SERVER)
                Serial.print("Reply received from the server: ");
                return in.message;

        Serial.print("Retrying, ");

I have an Apache server running on Ubuntu 18.10 with a PHP project running on port 80. The testConnection.php page takes 2 GET parameters (integers) and returns the sum.

Problem: It says that ESP module is not working. The AP in my case is a local hotspot on my mobile.

I have tried running the given example "SerialESP8266_library_test" and confusingly enough, it prints that it has successfully connected to my AP, but on my phone I do not see it connected. Only 1 device is visible as connected, which is my laptop which is running the Apache server and the web project. Also connectToAP returns 1, and connectToServer returns 0.

What am I doing wrong? I know that the ESP module requires power and the Arduino 3V3 is insufficient but I am just testing the code right now and I will do the required changes later on. Due to this, I am placing my Android phone just beside the ESP module so that it has no problems connecting to it.

Any help would be greatly appreciated! Thanks in advance.

  • 1
    swSerial.begin(115200). I don't think softwareSerial can even run that fast. The library you are using for wifi uses 9600 baud. I'd give that a try. – Gerben Nov 23 '19 at 13:47
  • @Gerben Some modules are 9600, some are 115200 - it depends on the version of the firmware. SoftwareSerial can run at 115200, but it can't react fast enough to incoming bytes to reliably receive a stream of data. – Majenko Nov 23 '19 at 14:07
  • @Juraj The WiFiEspAt requires flashing with AT 1.7, I did not want to do that – APN Nov 23 '19 at 14:08
  • @Gerben I tried with 9600 and made some other changes. Now, it correctly connects to the AP (shows up on my phone), also connects to the server. But receives a HTTP 400 Bad request error. Is there any problem in the GET request format? My page is at: – APN Nov 23 '19 at 14:10

Finally it is working by setting baud rate to 9600 and shortening the GET URL. Maybe there is a length restriction in the library.

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