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Flashing NodeMCU Firmware on ESP Board

NodeMCU is popular firmware for ESP8266 WiFi SoC. When you buy a NodeMCU ESP8266 board, it must have been flashed with the firmware. But, you can also flash it anytime by yourself, for example when you want custom NodeMCU firmware. For complete documentation of NodeMCU, you can see it here. There are a few steps to flash your board firmware. In this example, I use NodeMCU DevKit 1.0 with ESP-12E core which is easy to get in the market. If you use ESP-01, you need to see my other post about the ESP-01 flashing circuit.

1. Build the firmware. The easiest way is to build from the cloud, just follow the steps then the firmware will be sent to your email.

2. Install It is a python application to communicate with the ESP ROM bootloader. You can install it either from python package manager using pip install esptool or download manually from Github repository here.
$ git clone
There are several other tools that you can use to flash the firmware, for example, NodeMCU PyFlasher with GUI which is also based on

3. Erase existing flash using In this example, my bord is connected to port /dev/ttyUSB0 with baud rate 9600.
$ ./ --port /dev/ttyUSB0 --baud 9600 erase_flash

4. Then, you can run again to flash the firmware into your ESP board.
$ ./ --port /dev/ttyUSB0 --baud 9600 write_flash --flash_mode dio 0x00000 ../nodemcu-firmware/nodemcu- 
The flash_mode is dio because the board flash memory size is greater than or equal to 4MB. If you use a board with a smaller memory size such as 512kB or 1MB like in ESP-01, the mode should be qio.

5. After the fourth step, your ESP board still cannot be programmed because the board needs SDK init data. All data in flash memory had been erased through the third step. The SDK init data is required to make firmware boot correctly and saved in the fourth sector from the end of flash memory. If you try to upload a certain Lua program file using nodemcu-tool it will always show an error message as follows.
[NodeMCU-Tool] Unable to establish a connection - Timeout, no response detected - is NodeMCU online and the Lua interpreter ready?
So, the next step is to download SDK init data from this repository. You can clone it and find the binary file in bin directory.

6. Upload the SDK init data to the correct address based on your board flash memory size. As I use NodeMCU DevKit 1.0 with 4MB of flash memory, the location is at 0x3fc000. If you use ESP-01 with 1MB of flash memory, it's at 0xfc000. You can see full information about SDK init data here. The process is the same as flashing the firmware.
./ --port /dev/ttyUSB0 --baud 9600 write_flash --flash_mode dio 0x3fc000 ../ESP8266_NONOS_SDK-2.1.0/bin/esp_init_data_default.bin

7. Now, you can try to run certain commands using any NodeMCU tool like nodemcu-tool. From my experience, after flashing the firmware, I need to redo certain commands a few times before it can work properly. For example, I run the following command four times before it can connect with the device.
$ nodemcu-tool mkfs --port /dev/ttyUSB0 --baud 9600
[NodeMCU-Tool] Do you really want to format the filesystem and delete all file ? (no) yes
[NodeMCU-Tool] Connected
[NodeMCU] Version: 2.1.0 | ChipID: 0x3bb3a4 | FlashID: 0x1640c8
[NodeMCU] Formatting the file system...this will take around ~30s
[NodeMCU] File System created | format done.

8. Done. Now, you can upload the program to your board. I prefer to use ESPlorer with GUI rather than nodemcu-tool.

ESP8266 WiFi NodeMCU 


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