softwareserial between arduino uno and esp8266

Question

I have an Arduino UNO and HUZZAH ESP8266 module. I need to send data between Arduino UNO and ESP module via Software Serial. Right now I have the ESP module write data and Arduino UNO display data, but not working. When I run the Arduino UNO and open its Serial Monitor, nothing is printed using below source code.

1. ESP8266 RX PIN connected to Arduino UNO PIN 2.
2. ESP8266 TX PIN connected to Arduino UNO PIN 3.
3. Using the FTDI cable that came with HUZZAH ESP8266 to power this module. I just individually connected the RX and TX pins to the ARDUINO PIN 2 and 3 as mentioned above.

Any ideas what why not working? Below is code for both modules. Thanks,

Arduino UNO

#include <SoftwareSerial.h>
SoftwareSerial ESPserial(2, 3); // RX | TX
void setup(void){
 //Start hardware Serial communication
 Serial.begin(115200);
 //Start the software serial for communication with the ESP8266 component
 ESPserial.begin(57600); 
}
void loop(void){
if (ESPserial.available()){
 Serial.println("ESP available!!!");
 Serial.println(ESPserial.read());
}
}

HUZZAH ESP8266

#include <ESP8266WiFi.h>
#include <SoftwareSerial.h>
SoftwareSerial ESPserial(2, 3); // RX | TX
void setup(void){
 //Start the software serial for communication with the Arduino UNO component
 ESPserial.begin(57600);
 //TODO: setup Wifi
}
void loop(void){
 ESPserial.write("This message generated by ESP module.");
 delay(500);
}

• Rrz0: What is the Arduino Pin 2 ?
• Ron Beyer: RX on the Arduino should be connected to TX on the esp and vice versa, looks like you have RX connected to RX...
• Marquinio: The Arduino pin 2 is digital.
• Rrz0: @Marquinio yes but is it TX or RX?

Answer 1

Make sure that:

1. RX pin on the Arduino UNO is connected to the TX pin on the ESP8266.
2. TX pin on the Arduino UNO is connected to the RX pin on the ESP8266.
3. Baud rate should be set to the same value from both the Arduino and ESP8266.

I don't know about your arduino but looking at this schematic, your RX and TX should be swapped.

enter image description here

• John Smith: This is a very common mistake which at first may not seem obvious.
• Marquinio: Yes this fixed my problem. The ESP now gets data which seems to be in bytes. I will try to figure out how to send/read readable strings, but thats another story. My electronics knowledge is very limited, thanks.

Answer 2

Adding to the above answer. UNO's TX is at 5V , while ESP8266 's RX is at 3.3V, as it is a 3.3V module. So its better to use a resistive divider to bring UNO' TX to 3.3V and then feed to ESP's RX, instead of directly connecting them eachother.

• linhartr22: And conversely, the 3.3V TX pin of the ESP8266 is usually enough to drive the Uno's 5V RX pin.

Answer 3

//ESP

#include "SoftwareSerial.h"
SoftwareSerial ArduinoUno(D2,D3); //Rx, Tx
void setup() {
Serial.begin(9600);
ArduinoUno.begin(4800);
pinMode(D2, INPUT);
pinMode(D3, OUTPUT);
}
void loop() {
}
/******************************************************************************/

//UNO

#include "SoftwareSerial.h"
SoftwareSerial ArduinoUno(3,2); //Rx, Tx
void setup() {
Serial.begin(9600);
ArduinoUno.begin(4800);
}
void loop() {
 if(ArduinoUno.available() > 0){
 //float val = ArduinoUno.parseFloat();
 Serial.println(ArduinoUno.read());
 }
 delay(30);
}

• MichaelT: format your code properly (CTRL+K)