Flash ESP8266 over an Arduino

How to flash your ESP8266 without a USB-Serial adapter but with an Arduino.

First be sure everything is connected correcly:

Arduino	ESP82666
TX	RX
RX	TX
GND	GND
GND	GPIO-15
VCC (3.3V)	VCC (3.3V)
12	GPIO 0
13	CH_PD (EN)

The last 2 pins can be changed in the code.

Or set them manually:

PIN	Mode
CH_PD (EN)	HIGH (3.3V)
GPIO-0	LOW (GND)

Then upload this to your Arduino:

int program_pin = 12;
int enable_pin = 13;

void setup()
{
  Serial1.begin(115200);
  Serial.begin(115200);
  pinMode(enable_pin, OUTPUT);
  pinMode(program_pin, OUTPUT);
  digitalWrite(program_pin, LOW);
  digitalWrite(enable_pin,HIGH);
}

void loop()
{
  while(Serial1.available()){
    Serial.write((uint8_t)Serial1.read());
  }

  if(Serial.available()){
    while(Serial.available()){
      Serial1.write((uint8_t)Serial.read());
    }
  }
}

This code will let the Arduino send every byte it gets from the PC over Serial to the ESP8266 and back.

So now you can flash your ESP with the esptool or the nodemcu-flasher over the COM-port of the Arduino.

XaviTorello/arduino_flash_esp8266.md