Comment by melastmohican
12 hours ago
Hi HN,
I’ve been experimenting with the new Raspberry Pi Pico 2 W (RP2350) and wanted to see how difficult it would be to build a fully compliant Matter smart device from scratch using Rust.
I put together a complete "Blinky" example using the rs-matter stack and the embassy async framework. It uses BLE for the initial commissioning phase and Wi-Fi for network connectivity. Once flashed, you can provision it directly into Apple Home, Google Home, or Home Assistant using your smartphone—no cloud accounts required. It exposes a standard Matter On/Off cluster that toggles a physical LED wired to the GPIO pins.
A few interesting technical notes from the build:
Bare Metal: It runs entirely no_std on bare metal using embassy-rp. Radio Coexistence: Getting the CYW43439 wireless chip to handle concurrent BLE (for commissioning) and Wi-Fi (for Matter IP traffic) on the RP2350 took some tweaking. We actually had to dial back the PIO SPI clock divider specifically because the RP2350's faster 150MHz core clock was causing bus corruption when the radio was saturated! Async Rust: The repo includes the full async CoEx (coexistence) runner setup to safely multiplex the radio between the Bluetooth and Wi-Fi stacks concurrently. If you’ve been wanting to build local-only smart home devices but felt intimidated by the massive official C++ Matter SDK, doing it in Rust is actually becoming incredibly approachable.
Would love to hear if anyone else is building custom smart home gear in Rust.
This looks very interesting. Thanks for sharing!
> bus corruption when the radio was saturated
How do you even diagnose this?
The initial approach was to run BLE and Wi-Fi simultaneously. Provisioning sometimes worked. It seems like there was some interference. Then switched to run BLE with Wi-FI off. When I got Wi-Fi credentials, switched BLE off, and turned Wi-Fi on. It still had some issues. Turned out when slowed down SPI bus, it started working. Only tested with Home Assistant and have to fork and patch rs-matter-embassy
re: wifi/ble together
That sounds like the crate didn't have coexistence enabled or the defaults were really odd - so much boring stuff to write about BLE/WiFi Coex, but the short is "the default settings" are pretty good for low bandwidth IoT devices.
I'll peek at the code out of interest :)
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Use a digital storage scope, many of them can directly decode protocols like SPI . Then a lot of trial and error to figure out when exactly the issue happens and what else is happening around that time.