Kameleon Core


Kameleon core is a small-sized and powerful electronics development board that runs Kameleon JavaScript runtime. It can be connected to PC via micro USB-cable and controlled by typical terminal program as well as Kameleon Web-based IDE.




38mm x 21mm


STM32F411CEU6 (ARM 32-bit Cortex M4)

Clock Speed


Operating Voltage


Input Voltage

3.55V ~ 6V

Flash Memory

512KB (80KB for user code)




20 (Up to 20mA for Pin 0~19, 3mA for Pin 19) .


5 (450KHz ~ 1Hz)









On-board LEDs

2 (1 for power, 2 for user)

On-board Buttons

2 (1 for reset, 1 for user)


You could supply the power through Micro USB Port or VBUS pin. The operation input voltage is minimum 3.55V, maximum 6V and maximum 500mA current (500mA resettable fuse is on the board) is capable for this board. If you drive the high current device like a big motor, you have to use the external power source with a relay circuit.

Micro-USB type B (5V) input is the most convenient way to supply the power. You can use the Travel Adapter for your smartphone (5V, 500mA or higher) or USB2.0/3.0 port which can supply more than 500mA. If you want to use the battery for the production, you should consider the voltage (3.55V ~ 6.0V) and current (up to your application).

Pull-Up Resistors for I2C

A pull-up resistors are needed for I2C SCL and SDA pin and external pull-up resistors are recommended for Kameleon Core.

For your convenience, Kameleon Core I2C port has 40 KOhm internal pull-up resistor. You may not need external pull-up resistor if your I2C clock speed is low enough (internal pull-up may be enough if the clock is low)

For the high speed I2C operation, you have to use external pull-up resistor. The 10 KOhm resistor is enough to operate I2C fast mode (400 kHz) in most cases. Since there are internal resistors, the total pull-up resistor value is the parallel resistance of internal and external pull-up resistor. If you put 10 KOhm external pull-up resistors, the total pull-up resistance is 8 KOhm. (the parallel resistance of 40 KOhm and 10 KOhm)

The Kameleon Core has pads for I2C external pull-up resistors. You could put 0603 SMD type resistors on the Kameleon Core. The pads for the pull-up resistors are shown below.

Special boot mode

Firmware update mode

Turn on Kameleon Core board pressing the BTN0, the Kameleon core board would go to the firmware update mode. A user can update new FW using Kameleon CLI tool via USB port. See the Firmware Update section in this document.

  1. Pressing BTN0 button before supply the power of the Kameleon Core board.

  2. Supply power to the Kameleon Core board using PC USB port and release the BTN0.

  3. The Green LED is blinking in the Firmware update mode.

Safe mode - Do not load a user JavaScript code.

Turn on Kameleon Core board and pressing the BTN0 button at 1sec, the Kameleon board would go to Safe mode and do not load a user JavaScript code which is loaded in the flash. This mode might be used when a user JavaScript code make any issue, so a user can't upload new code to the Kameleon Core board.

  1. Supply the power to the Kameleon Core board.

  2. Press BTN0 before 1sec.

  3. Keep pressing BTN0 for 1sec.

  4. Release the BTN0.

Firmware Update

Typically firmware is automatically updated by Kameleon Agent and Kameleon Web Editor. Nonetheless to update firmware manually, please proceed the following instructions:

Firmware update using Kameleon CLI tool via USB port.

  1. Install Kameleon CLI (Command Line Interface).

    $ npm install -g kameleon-cli
  2. Download latest firmware binary from releases page of the Github repository of Kameleon JavaScript runtime. (e.g. kameleon-core.bin for Kameleon Core board).

  3. Update firmware using Kameleon CLI.

$ kameleon update <firmware> -p <port>
# e.g.) kameleon update kameleon-core.bin -p /dev/tty.usb001A
# e.g.) kameleon update kameleon-core.bin -p COM6

Firmware update using DfuSe Demo tool via USB port.

Windows OS only, Provided by ST-Micro.

  1. Download and install DefSe Demo tool.

  2. Install STM DFU mode driver.

    The driver installation file is in the C:\Program Files (x86)\STMicroelectronics\Software\DfuSe v3.0.6\Bin\Driver folder.

  3. Supply 3.3V to BT0(BOOT0) pin on the Kameleon Core board and tune it on using PC USB port in order to go into STM DFU mode.

  4. Check "STM Device in DFU Mode" USB controller in windows Device Manger.

  5. Generate DFU file, kameleon-core.dfu from the firmware hex file, kameleon-core.hex using Dfu File Manager tool.

    1. Run DFU file manager tool and select "I want to GENERATE a DFU file from S19, HEX or BIN files".

    2. Click "S19 or Hex..." button and select kameleon-core.hexfile.

    3. Click "Generate..." button and write the DFU file name like kameleon-core.dfu.

  6. Run DefSe Demo tool and open the DFU file, kameleon-core.dfu.

    1. Click "Choose..." button in the "Upgrade or Verify Action" box and select the kameleon-core.dfu.

  7. Update(Upgrade) the firmware.

    1. Check "Verify after download" checkbox in the "Upgrade or Verify Action" box.

    2. Click "Upgrade" button in the "Upgrade or Verify Action" box to update the firmware.

    3. Check the "Target 00: Upgrade successful !" message.

  8. Remove 3.3V input of the BT0(BOOT0) pin on the Kameleon Core board and reset the board.

Must have ST-LINK/V2 in-circuit debugger/programmer for STM32. Windows OS only, Provided by ST-Micro.

  1. Download and install STM32 ST-LINK Utility

  2. Connect Kameleon SWD port to ST-LINK/V2 port

  3. Run STM32 ST-LINK Utility

  4. Select the "Connect" in the "Target" menu.

  5. Select the "Program & Verify..." in the "Target" menu.

  6. Click "Browse" button and select kameleon-core.hexfile and click "Start" button to update firmware.

Bootloader Update

Bootloader code could be updated using DfuSe Demo tool or ST Link/V2 tool. All the process is the same as firmware update except the kameleon-core-bootloader.hexfile is used instead of the kameleon-core.hexfile.