Nokia 3310 F-Bus Adapter

A 3D printed F-Bus adapter for Nokia 3310 cell phone

Similar projects worth following
I have an old Nokia 3310 mobile phone lying around for which I forgot the security code and I want to reset it to defaults and change some of its configurations.
I couldn't find a F-Bus adapter online, because of that I thought to make such adapter myself..

What is F-Bus?

The F-Bus is a full-duplex bus. It uses one pin for transmitting data(Tx) and one pin for receiving data(Rx). It's baudrate is 115200bps, 8 data bits in each character, no parity, one stop bit.

After little online research for the F-Bus I found that the F-Bus is based on UART and all I need is a digital isolation for Rx/Tx lines to solve the difference in voltage issue and isolate the device if it is powered from another source, so for this I used the ADuM1201.

F-Bus pinout:

The Power Supply:

For the supply I used a mini step down converter and set it to value between 3.7V and 3.8V, the USB is enough to power the device so there's no need for an external one (the device could consume up to 1W).

The phone's battery has four pads (details on 3310 battery types):

  1. VBATT, battery voltage, rated: 3.7V and its connected to the output of step down converter;
  2. BSI, battery size indication and it depends on the battery type, basically this pin is a pull-down resistor of a specific value (I used 73k7, 3 smd resistors in series);
  3. BTEMP, battery temperature, it is also a pull-down resistor (I used a 47k);
  4. GND, the ground.


F-Bus pinout

JPEG Image - 100.15 kB - 12/21/2021 at 00:20


Communication testing script, to run it create a python virtual environment and install in pyserial, or just run it if you have already pyserial installed in your main Python3. The script is just to show that the adapter is working, to establish a proper communication the comm. protocol implementation is needed. This will be the next project.

x-python - 527.00 bytes - 12/20/2021 at 22:32



The F-Bus pogo pin holes are designed for a 2mm in diameter pin socket and they need to be widened with a 2mm drill bit. The widening is easy and can be done by hand.

sla - 274.30 kB - 12/20/2021 at 20:53


  • 1 × ADuM1201 Semiconductors and Integrated Circuits / Misc. Semiconductors and Integrated Circuits
  • 1 × Mini DC-DC converter, any 5V to 3.7V converter
  • 4 × pogo pins 2mm in diameter

  • Security code reset!

    Johnny01/12/2022 at 20:05 0 comments

    I managed to reset the security code!

    As follows:

     1. enable extended commands (0x64 0x01)

    1e 00 0c 40 00 06 00 01 64 01 01 41 77 07 

     2. set new code command and the new code is 12345 (see bytes 31 -> 35):

    1e 00 0c 40 00 0c 00 01 6f 01 31 32 33 34 35 00 01 46 4b 0c 

     3. disable extended commands (0x64 0x00)

    1e 00 0c 40 00 06 00 01 64 00 01 40 77 07

    I'll explain the frame later.

  • LCD test via FBus

    Johnny01/12/2022 at 17:20 0 comments

    Due to lack of a detailed documentation I had to do it by trial and error, after few tries, I was able to run the LCD test via FBus.

View all 2 project logs

Enjoy this project?



Similar Projects

Does this project spark your interest?

Become a member to follow this project and never miss any updates