Alternative flashing methods

NOTE: When you have already flashed the stick and paired devices to it, reflashing it requires to re-pair all your devices!

Via Arduino/ESP8266

Flashing firmware via Arduino is implemented using the project But with minor improvements!!!

AndrewLinden described that he was able to flash CC2531 using CCLib with comments.

As described I made a fork of the CCLib library with minor changes for flashing firmware via Arduino:

Flashing proccess:

  1. Download and unpack the archive with the library

  2. Flashing Arduino sketch via Arduino IDE CCLib\Arduino\CCLib\Examples\CCLib_proxy\CCLib_proxy.ino

If flashing via esp8266 (wemos d1 mini), you need change connection (p. 5) and Pinout configuration in Arduino/CCLib/Examples/CCLib_proxy/CCLib_proxy.ino:

int CC_RST   = 5;
int CC_DC    = 4;
int CC_DD_I  = 14;
int CC_DD_O  = 12;
  1. Install Python 2.7 or later (tested with python 2.7.13), if not installed

  2. Install pyserial 3.0.1, if not installed pip install -r CCLib\Python\requirements.txt or pip install pyserial==3.0.1

  3. Connect the contacts as described But in my case, I connected completely without resistors, combined the contacts CC_DD_I and CC_DD_O together and connected to the DD pin of the DEBUG connector!

I connected only 3 specified contacts and GND. During the firmware, the stick and Arduino must be connected to the USB.

  1. After that, try to get information about the chip - if it works, then the connection is correct (example for COM9 port - Arduino port):
C:\Projects\CCLib\Python>python -p COM9
INFO: Found a CC2531 chip on COM9

Chip information:
      Chip ID : 0xb524
   Flash size : 256 Kb
    Page size : 2 Kb
    SRAM size : 8 Kb
          USB : Yes

Device information:
 IEEE Address : 00124b0014aa
           PC : 0000

Debug status:

Debug config:

Another example of connection on MacOS

  1. If everything is successful, download the firmware. Before we flash the firmware we need to make a modification to it. Open the .hex file in a text editor and remove the second last line. Now save the file.

  2. Start the flashing firmware (it takes a long time, about 2-3 hours):

C:\Projects\ZigBee>python -e -p COM9 --in=CC2531ZNP-Pro-Secure_LinkKeyJoin_mod.hex
INFO: Found a CC2531 chip on COM9

Chip information:
      Chip ID : 0xb524
   Flash size : 256 Kb
    Page size : 2 Kb
    SRAM size : 8 Kb
          USB : Yes
Sections in CC2531ZNP-Pro-Secure_LinkKeyJoin_mod.hex:

 Addr.    Size
-------- -------------
 0x0000   8176 B
 0x1ff6   10 B
 0x3fff0   1 B
 0x2000   239616 B

This is going to ERASE and REPROGRAM the chip. Are you sure? <y/N>:  y

 - Chip erase...
 - Flashing 4 memory blocks...
 -> 0x0000 : 8176 bytes
    Progress 100%... OK
 -> 0x1ff6 : 10 bytes
    Progress 100%... OK
 -> 0x3fff0 : 1 bytes
    Progress 100%... OK
 -> 0x2000 : 239616 bytes
    Progress 100%... OK


Via Arduino Uno/CCLoader

This has only been tested with a Genuine Arudino Uno (and an Arduino Pro Micro - China clone), but is significantly faster

  1. Download and unpack CCLoader firmware and tools

  2. Download the correct firmware, this example will be using the CC2531 firmware.

  3. Unpack firmware and convert the hex-file to bin.

  4. Under Windows: (not tested by me) objcopy.exe –gap-fill 0xFF –pad-to 0x040000 -I ihex CC2531ZNP-Prod.hex -O binary CC2531ZNP-Prod.bin Place the resulting CC2531ZNP-Prod.bin in the Windows folder of CCLoader with CCLoader.exe.

    Under Linux: objcopy –gap-fill 0xFF –pad-to 0x040000 -I ihex CC2531ZNP-Prod.hex -O binary /tmp/CC2531ZNP-Prod.bin

objcopy is part of the bintools package.

  1. Flash Arudino Uno with Arduino\CCLoader\CCLoader.ino, note the COM port number/device this will be used later

  2. Connect pins as described to debug header

Arduino | CC Header
4 -> RESETn
5 -> DC (Debug Clock)
6 -> DD (Debug Data)

If you have a 3.3V Arduino you can optionaly connect

3.3V -> Target Voltage Sense (Pin 2)

and programm the CC2531 without connecting the CC2531 to USB (in the next step).

  1. Connect Arduino first, then within a couple seconds connect the CC2531 to USB power

  2. Under Windows - open a command window in the Windows folder with CCLoader.exe

Under Linux you have to compile CCLoader first - so change to CCLoader/SourceCode/Linux, and run gcc main.c -o CCLoader.

  1. Under Windows start the flash with CCLoader_x86_64.exe COMNUM CC2531ZNP-Prod.bin 0

Under Linux start the flash with ./CCLoader USBDEV CC2531ZNP-Prod.bin 0

If burning fails/gets stuck at “Request sent already! Waiting for respond…” - try again, check your wiring, try using “1” instead of “0” as the last parameter.

With Raspberry

  1. Install wiringPi, if not already installed.

  2. Install flash_cc2531 :
    git clone
  3. Connect the following pins of the debug port to the GPIO port :
    • pin 1 (GND) –> pin 39 (GND)
    • pin 7 (reset) –> pin 35 (GPIO24, BCM19)
    • pin 3 (DC) –> pin 36 (GPIO27, BCM16)
    • pin 4 (DD) –> pin 38 (GPIO28, BCM20)

As with the arduino option above, connecting Target Voltage Sense to a 3.3v source eliminates the need to plug the device into a usb port, so optionally connect the following too:

See above for the dispositions of pins on CC2531, and at for pins on Raspberry.

A downloader cable CC2531 and 4 Dupont line Female to Female are perfect for this purpose.

Now insert the usb dongle in an USB port :

  1. Test by running :
cd flash_cc2531

it should return :

  ID = b524.

If you see 0000 or ffff, something is wrong and you should probably check your wiring.

  1. Download and extract the latest firmware
cd ~/flash_cc2531       #assumming you git-cloned the program to your home directory
  1. Erase and flash the CC2531 :
./cc_write CC2531ZNP-Prod.hex

It takes around 3 minutes.