Radio card for 802.15.4 based on nRF52

Creators & Developers Expansion Card
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I’d love to have a module around that can connect my Framework laptop with an 802.15.4 network, typically 6LoWPAN (same radio as Zigbee). A widely available chip for that is the nRF52 family (eg. nRF52840), which has a Cortex-M core, a USB 2.0 interface and a 802.15.4/BLE/proprietary radio.

Given radio stuff is hard and components are fiddly, it could be built from a SMT module such as the MDBT50Q-1MV2. At a first glance, the 2.1mm high module could fit well on the bottom side of the retrofit expansion card; the screw positioning might be detrimental to the antenna performance.

Usage-wise, this could do either of two things:

  • Serve as an 802.15.4 adapter. This probably needs a custom driver and firmware.
  • Serve as an 802.15.4 NIC. A trivial program in RIOT OS could provide full access to an 802.15.4 network, and expose the link as an Ethernet card.
  • Act as a remote access to the Debug Accessory Mode of the EC (probably needs a few resistors and probably a solder jumper).
  • Custom development: Such a module would enable RIOT OS users to always have an embedded module at hand, which they can use and flash without extra peripherals. Programming would be done via bootloader; as a failsafe, it’d be good to have exposed pads to attach a debugger.

BOM-wise, I think this could be literally just the USB plug and the SMT module (usage as DAM could need a few small parts).

Is there anything that should be reasonably added just because it’s trivial (and doesn’t cause trouble when not populated)?

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Would an SDR fit the bill for what you’re trying to do? I’ve seen them used to work with Zigbee in the past. If so, resources might be best spent finding one that you can strip down far enough to fit inside an expansion card housing.

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As @John_Mayson shared in another thread, the internals of a Nooelec NESDR Nano 3 fit pretty well in the USB-A expansion card housing with only a small USB-C to A adapter required. No advanced skills required.

It does stick out of the housing a little bit, although if you do have soldering skills you could probably replace the USB-A connector on the Nano 3 with a USB-C connector and get it to fit fully.

SDR Expansion Card
SDR Expansion Card1920×1080 160 KB

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For serving as an 802.15.4 radio, probably yes. I have no clue what software stack would be there, or how Linux’ 802.15.4 stack could be made to talk with it, but I’m generally positive when it comes to things that are just a software problem.

For the other use cases, I’d still need a microcontroller on board (and it’d need to be fast enough to do SDR). In particular, the “have an embedded development board always in-device” use case is something I’d be missing – but then again, this probably has a small target audience.

At any rate, it’d be a lot more expensive if the SDR features are not used, and configuration would be more manual.