< up >
2026-05-13

Flashing OpenThread Firmware on Smlight SLZB-07

Matter/Thread is still experimental and getting started took me some time. I distilled the steps to flash the OpenThread firmware onto the smlight slzb-07 without the online flasher below.

Official procedure

The official device update manual suggest to use the online flasher. In my case this didn’t work out with various browsers on different computers.

What didn’t work for me:

• firefox doesn’t support Web Serial, yet
• chromium supports Web Serial, finds the device but the updater fails with firmware not found or similar
• the alternate web flasher didn’t work either
• Home Assistnat Silaps Flasher app could detect but not connect to the device

Locate firmware

Find latest open-thread firmware on github . Look for file starting ot for open-thread with the device name slzb-07 (without any suffix) and ending with baud rate 460800. The baud rate is later used to configure the Home-Assistant integration.

As of today (10.05.2026): ot-rcp-v2.4.5.0-slzb-07-460800.gbl

Enter flash mode

1. Open the case:
   • use screw driver or similar
   • it’s normal to be fiddly
2. Short the FLASH and GND pin holes:
   • locate the two pin holes labeled FLASH and GND on the PCB.
   • use a wire or similar, I bended a paperclip into a u-shape
   • keep them shorted over the whole flashing process
3. Plugin via USB:
   • plug the stick into your USB-Port
4. Find device:
   • look into dmesg to find the exact one¹
   • device should now be available via /dev/ttyUSB0 (or similar)
5. Verify flashmode:
   • you may need sudo or put the device into the dialout group first
   • initiate connection via picocom -b 115200 /dev/ttyUSB0
   • press any key
   • you should see something like this:

Gecko Bootloader v2.03.01

1. upload gbl
2. run
3. ebl info
BL >

Flashing

1. Use picocom and sz (or for arch users lrzsz-sz).
2. connect to device via sudo picocom --send-cmd="lrzsz-sz -vv -b -X" -b 115200 /dev/ttyUSB0²
3. press 1 to select upload gbl in Gecko bootloader menu
4. press ctrl-a and ctrl-s sequentially to enter file upload
5. paste path to firmware

You should see some progress.

Don’t get confused by the 115200 baud rate. This is for talking to the gecko bootloader. The actual firmare will then use 460800.