Anders Frandsen | anfran.dk

Hi, I’m Anders.

Software Engineer | Embedded Systems · IoT

Open Source Contributions

STM32WL3x SoC & NUCLEO-WL33CC1 board support

Bring-up of the previously unsupported STM32WL3x SoC family in mainline Zephyr, merged upstream and validated on hardware.

Zephyr RTOS · STM32WL3x · STM32CubeWL3 HAL/LL

Personal Projects

Brew-by-weight control for a Rocket Espresso machine

Weighs the shot in real time and stops extraction at the target ratio, with a touchscreen UI and a custom PCB.

nRF52840 · Zephyr RTOS · KiCad

Battery-powered Sleepy End Device

A contact sensor on a custom PCB idling at 7.47 µA, commissioned end-to-end with Home Assistant.

nRF52840 · Zephyr RTOS · Matter · OpenThread · KiCad

Matter over Thread Door Sensor

A battery-powered Matter-over-Thread door sensor acting as a Sleepy End Device (SED). Commissioning is validated end-to-end with Home Assistant on a Raspberry Pi running an OpenThread Border Router via an nRF52840 dongle.

3D-printed door sensor enclosure with magnet block — Closed enclosure with magnet block

Door sensor enclosure opened with the PCB installed — Opened, with the PCB installed

Device Data Model

Endpoint 0: Root Device

Cluster	ID
Basic Information	`0x0028`
Power Source	`0x002F`
ICD Management	`0x0046`
Network Commissioning	`0x0031`
Operational Credentials	`0x003E`
General Commissioning	`0x0030`
Thread Network Diagnostics	`0x0035`
General Diagnostics	`0x0033`
OTA Software Update Requestor	`0x002A`
Access Control	`0x001F`
Administrator Commissioning	`0x003C`
Group Key Management	`0x003F`
Descriptor	`0x001D`

Endpoint 1: Contact Sensor `0x0015`

Cluster	ID
Boolean State	`0x0045`
Identify	`0x0003`
Descriptor	`0x001D`
Software Diagnostics	`0x0034`

Boolean State reports whether the door is open or closed. StateValue is false = closed, true = open.

Power Consumption

Power measurements taken with a Nordic Power Profiler Kit (PPK).

Idle: ICD SIT (Short Idle Time) mode

As a Sleepy End Device polling on a 15 s interval, the average current over 1 minute is 7.47 µA (max 9.11 mA during radio activity).

Measuring between the polling spikes gives 5.84 µA, which is closer to the true idle floor and what the average would be in ICD LIT (Long Idle Time) mode (WIP).

Door open

While the door is open the average current is 2.51 mA, driven mainly by the status LED being on.

Hardware used

Endpoint Device

Platform: Nordic nRF52840-DK (development)
MS88SF2 module (for PCB)
Adafruit magnetic reed switch

The PCB v1.0 uses a MS88SF2 module, a CR2032 coin cell, a 14-pin STDC14 header for J-Link flashing/debugging.

Door sensor PCB front — Front: CR2032 holder, reed switch, and antenna keep-out

Door sensor PCB module side — Back: MS88SF2 (nRF52840) module

Thread Border Gateway

Raspberry Pi 4B
Nordic nRF52840 Dongle

Preparing the dongle as a Radio Co-Processor (RCP) is straightforward: follow this guide. Once the firmware is installed, set up Home Assistant on the Raspberry Pi, connect the USB dongle, then install both the OpenThread Border Router (OTBR) and Matter Server add-ons to enable Thread and Matter support.

Software and tools

Zephyr RTOS for firmware
OpenThread stack
Home Assistant
KiCad for PCB design