How to Program ESP-01 with Arduino IDE

To program an ESP-01 module with Arduino IDE, the module needs to be connected to a programmer adapter. What keeps the ESP-01 module apart from other ESP8266-based microcontroller modules is the absence of a UART interface. Hence, a programmer adapter is required or it can be wired with a USB to TTL converter to create a programmer.

ESP-01 Programmers

ESP-01 USB-to-Serial Converter Programmer Module

The ESP-01 programmer module shown in Figure 1 uses the Silabs CP2104 USB-to-serial converter chip. Other ESP-01 programmer modules use the CH340 chip. With this kind of programmer module, you do not have to worry about switching the ESP-01 module from RUN mode to PROGRAMMING mode. ESP-01 modules have what we call boot modes (see Table 1 below). That is, when they are powered up or when they are reset, depending on the state of the GPIO0 pin, they either RUN the program on their flash memory or enter into PROGRAMMING mode. With the programmer module above, everything is automatic. The ESP-01 module automatically switches into PROGRAMMING mode when you hit the Upload button on the Arduino IDE.

DIY USB-to-serial Converter Programmer

If you do not have an ESP-01 USB-to-serial converter programmer module, you can make your own programmer if you have a USB-to-serial converter. Figure 2 shows some examples of USB-to-serial converters.

Picture of several kinds of USB-to-serial TTL converters that can be used for programming ESP-01 with Arduino IDE — Figure 2. USB-to-Serial (TTL) Converters

Below is an schematic diagram of an ESP-01 programmer using a USB to TTL converter module. This is the preferred ESP-01 programmer while breadboarding because all the ESP-01 pins are accessible.

Schematic diagram of a DIY ESP-01 programmer using a USB-to-serial TTL converter. — Figure 3. ESP-01 Programmer Using a USB-to-serial TTL Converter

About the Circuit

The three (3) 10k resistors are pull-up resistors necessary to ensure that the ESP8266 pins are on their proper logic levels. The two capacitors are optional components to increase the stability of the programmer. The 10 microfarad capacitor serves as an additional ac ripple filter while the 0.1 microFarad (100 nanoFarad) capacitor is used as high-frequency filter.

The RESET and PROGRAM switches are push-button switches. Pressing and then releasing the RESET switch will boot and run the program loaded in the flash memory. Pressing and releasing the RESET switch, while at the same time holding down the PROGRAM switch, will place the ESP-01 into the UART Bootloader mode, or go into programming mode. See the table below.

Again, the sequence of switch presses in order to go into programming mode is: press and hold down the PROGRAM switch, press and release the RESET switch, and finally release the PROGRAM switch.

Boot Mode Table

GPIO-2	GPIO-0	Boot Mode
HIGH	LOW	UART Bootloader (Programming Mode)
HIGH	HIGH	Run program in flash

Table 1. ESP-01 Module Boot Mode Table

Arduino Board as ESP-01 Programmer

Another option for an ESP-01 programmer is an Arduino board. You can use any Arduino board available – Arduino Uno, Arduino Nano, Arduino Mega, etc. Figure 4 is an schematic diagram of an Arduino Uno board used as an ESP-01 programmer. Note that it is exactly the same schematic diagram shown in Figure 3, only with the USB-to-serial converter being replaced by an Arduino Uno board. For more information about using an Arduino board as ESP-01 programmer, please see – ESP-01 and ESP-01S Pinout and Configuration.

Schematic diagram of an Arduino Uno board being used as an ESP-01 programmer. — Figure 4. Arduino Uno as ESP-01 Programmer

Programming using Arduino IDE

To program the ESP-01 using the Arduino IDE, the ESP8266 core for Arduino must first be installed. Please see, How to Set up Arduino IDE for ESP8266 Programming.

If you don’t have the Arduino IDE installed yet, and you’re using Windows 10, see: How to Install Arduino IDE on Windows 10.

The Blink Program

The first lesson for programming the ESP-01 with the Arduino IDE is the Blink sketch. Open the Arduino IDE, create a new sketch, then, copy and paste the Blink program below.

 void setup() {
  pinMode(LED_BUILTIN, OUTPUT);     // Initialize the LED_BUILTIN pin as an output
}
// the loop function runs over and over again forever
void loop() {
  digitalWrite(LED_BUILTIN, LOW);   // Turn the LED on (Built-in LED on ESP-01 is active LOW)
  delay(1000);  // Wait for a second
  digitalWrite(LED_BUILTIN, HIGH);  // Turn the LED off by making the voltage HIGH
  delay(2000);  // Wait for two seconds (to demonstrate the active low LED)
}

void setup() {

pinMode(LED_BUILTIN, OUTPUT); // Initialize the LED_BUILTIN pin as an output

}

// the loop function runs over and over again forever

void loop() {

digitalWrite(LED_BUILTIN, LOW); // Turn the LED on (Built-in LED on ESP-01 is active LOW)

delay(1000); // Wait for a second

digitalWrite(LED_BUILTIN, HIGH); // Turn the LED off by making the voltage HIGH

delay(2000); // Wait for two seconds (to demonstrate the active low LED)

}

Before uploading the sketch to the ESP-01 module, first, make sure that you have selected the right board which is “Generic ESP8266 Module”. Please refer to Figure 5.

Screenshot of the Arduino IDE showing how to select the right board. — Figure 5. Arduino IDE Board Selection

Also, make sure that the appropriate serial COM port for your ESP-01 programmer is selected. If it is your first time to use your ESP-01 programmer, you may have to install the device driver for your ESP-01 programmer.

Screenshot showing how to select the correct serial COM port prior to uploading a sketch. — Figure 6. Arduino IDE Serial COM Port Selection

After selecting the right board and the correct serial COM port, click the Upload button. Following a successful upload with the message “Done uploading” (see Figure 7), the blue built-in LED on your ESP-01 board should start flashing.

If the LED does NOT flash, you must be using a different version of ESP-01 module. You may have to change the “Built-in LED:” setting on the Arduino IDE. If you want to know why, please see the article entitled Difference Between ESP-01 and ESP-01S.