Building Custom Firmware

For your project you might want to use an Espruino WiFi (or other) board with firmware that has different features from the Espruino-supplied one. For instance you might want to add features, or remove some to make more room for storage.

You can do this just by creating your own file...

To get started (assuming you have an Espruino WiFi):

Note: The board name file should be only alphanumeric capitals or underscores, starting with a letter (no dashes or lowercase).

Make changes in

Here's what you might do to cut out some un-needed code and add support for a special LCD display type. For more info on the LCD_SPI_UNBUF, click here

See the comments in-line:

info : {
    # Give your board a new name eg. `MYESPRUINOWIFI`, or give
    # your board file the *same name*
    # as the existing file by choosing 'ESPRUINOWIFI'...
    'boardname' : 'MYESPRUINOWIFI',
    # Reduce number of variables in order to free up more heap/stack
    'variables' : 4000,
    # Create binaries with customised names
    'binary_name' : 'espruino_%v_wifi_MYESPRUINOWIFI.bin',
    'binaries' : [
      { 'filename' : 'espruino_%v_wifi_MYESPRUINOWIFI.bin', 'description' : "Custom Espruino WiFi build"},
    'build' : {
        'libraries' : [
    # Remove libraries that are not needed            
            #'TV', # If you're not using PAL TV output
            #'FILESYSTEM', # If you don't need to use SD cards
            'CRYPTO', 'SHA256', 'SHA512',
    # Add LCD_SPI_UNBUF to handle 16bit color tft lcd displays
     'makefile' : [
    # Remove WIZNET (Ethernet vi SPI) <- if no plan to use ethernet         
          # 'WIZNET=1', # Add support for W5500 by default

    # Set SPI buffer transfer size (for LCD_SPI_UNBUF)
    # add 6x8 font - a nice 255 character font

Build firmware for the custom board

Just run the following commands:

export RELEASE=1

make clean


The following files will be created:

  • espruino_2v06.83_wifi_MYESPRUINOWIFI.elf
  • espruino_2v06.83_wifi_MYESPRUINOWIFI.bin
  • espruino_2v06.83_wifi_MYESPRUINOWIFI.lst

You can also run make serialflash or make flash depending on the board to write the binary directly to the board.

Flash and check the custom firmware



={ free: 6950, usage: 50, total: 7000, history: 33,
  gc: 0, gctime: 6.34193420410, blocksize: 16, "stackEndAddress": 536987904, flash_start: 134217728,
  "flash_binary_end": 379352, "flash_code_start": 134283264, flash_length: 524288 }

And you now have a customised board firmware!

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