M17_3310

Mainboard replacement for the Nokia 3310/3330.

[!CAUTION] The board's thickness is 1.0mm. Anything thicker will not fit.

Original mainboard photos

Both photos in the misc directory are cropped, so that if you scale them for 108mm height, you should be able to make direct measurements using GIMP or other image editing software.

Interactive HTML BOM

An interactive HTML version of the Bill of Materials can be found here.

SA868S UHF module firmware

The RF module must be flashed with OpenRTX. It can be flashed before or after soldering it in place as the PCB has a hole through which the four programming pads are still accessible.

First of all, download and install the rl78flash utility. How you install it, depends on your operating system.

Now download the latest OpenRTX firmware for the SA868S UHF module. Here is an example for version 1.4.1:

# cd ~/Downloads
# wget https://github.com/OpenRTX/sa8x8-fw/releases/download/v1.4.1/sa8x8-fw-sa868s-uhf.s37

We now have the software and firmware in place but we need to build a small programming adapter. You can build one with a UART to USB converter, two 1N5819 diodes, some wire and a small PCB. Here's a diagram showing how it is connected:

Here is how it could look like:

For the four pins, cut and solder the legs of a few resistors to the front of the PCB and bend them to the spacing of the four pins of the SA868S. The rest is quite self-explainatory.

To flash the firmware, plug in the UART to USB converter, hold the board with the four pins to the SA868S module and execute the following command.

Note: Make sure to jumper the converter to 3.3V!

# cd ~/Downloads/rl78flash/
# flash % ./rl78flash -m 1 -a -v /dev/tty.usbserial-A50285BI ~/Downloads/sa8x8-fw-sa868s-uhf.s37
rl78flash v0.7.0
Protocol configuration: protocol=0, code_block=1024, data_block=1024
Erase code flash
Erase data flash
Read file "/Users/rz01/Downloads/sa8x8-fw-sa868s-uhf.s37"
Write code flash
Write data flash
Verify Code flash
Verify Data flash
Reset MCU

In this case, flash mode 1 (-m 1) was chosen as the UART to USB converter has a DTR pin. You might need to wire your adapter differently and then select another mode depending on your specific UART to USB board. Please consult this README and this diagram for more information on this.

[!NOTE] The device will appear frozen if the firmware running on the RF module is not OpenRTX.

Device firmware

See the example firmware here.

Flashing over USB

1. Plug in the USB cable.
2. Press and hold the OK button (large horizontal one with a blue bar, just below the display).
3. Press the power button at the top of the device.
4. Release the OK button.

The device should enter USB DFU mode and should be recognized by CubeProgrammer.