ESP-01 ESP8266 Module – Complete Programming Lessons (Beginner to Advanced)

If we are thinking of a low cost Wi-Fi module, then ESP-01 is one of the choice. While it is low cost module, resources are limited and programming the board is somewhat tedious if you did not read the datasheet properly. Here, I am listing some of the important programming lessons around ESP-01.

        Required Hardware for ESP-01 Programming

Programming has to be done through UART pins available on the module. So, to connect to laptop, we need USB to UART converter (CP2012, FTDI based,..) or an Arduino Uno board. You can refer this page for details.

          https://nematicslab.com/how-to-program-esp01/

        Common Errors While Programming ESP-01

• To program the ESP-01 module, the GPIO0 pin has to be pulled LOW. This enables the chip to go to bootloader mode.

• Once programmed, the GPIO0 pin has to be removed from LOW state and pulled HIGH (there is internal pull-up, so, we can keep it floating) to enable the chip to run the code

• If the board is not getting programmed and you know that HW connections are good, try to follow below procedure and try programming again

        After connecting GPIO0 to GND, ensure below sequence.

• Disconnect ESP power
• Reconnect 3.3V
• Press RESET once (RST → GND)
• Upload again
  
  
• There are only 2 main GPIO exposed on ESP-01 connector (if you are planning to use UART, left with only 2 GPIO), GPIO0 can be used for toggling or any GPIO operations.
• Ensure that the ENABLE pin (CH_PD) of the module is always pulled HIGH

• If you are connecting UART to USB converter to program the board, ensure that UART to USB is powered first and then the ESP-01 board

ESP-01 Example Codes (GPIO0)

    // Very small test for GPIO0 toggling + serial heartbeat

void setup() {

  Serial.begin(115200);

  delay(50);

  Serial.println("\n=== GPIO0 Toggle Test ===");

  pinMode(0, OUTPUT);

}

void loop() {

  digitalWrite(0, HIGH);

  Serial.println("GPIO0 = HIGH");

  delay(3000);

  digitalWrite(0, LOW);

  Serial.println("GPIO0 = LOW");

  delay(3000);

} 

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