IPC Radio Service

Radio service firmware for the nRF5340 network core. Provides 802.15.4 radio access to the application core via IPC shared memory.

This is a minimal Contiki-NG image whose sole purpose is to receive commands from the application core, call the nRF 802.15.4 radio driver, and return results.

Building and Flashing

The network core must be flashed before the application core:

make -C examples/platform-specific/nrf/ipc-radio-service \
     TARGET=nrf BOARD=nrf5340/dk/network
make -C examples/platform-specific/nrf/ipc-radio-service \
     TARGET=nrf BOARD=nrf5340/dk/network ipc-radio-service.upload

Optional: nrf_802154 radio with hardware auto-ACK

By default the service uses the raw radio driver (nrf-ieee-driver-arch.c), which does not acknowledge frames in hardware; the IPC MAC sends software ACKs instead, which can be too slow for some peers.

Building with NRF_802154=1 replaces the raw driver with Nordic’s nrf_802154 library, which performs address filtering and auto-ACK in hardware within the 802.15.4 ACK window, and reports the transmit verdict (ACK received or not) over IPC.

Both cores must be built with the same setting. The application core needs NRF_802154=1 too, so that CSMA trusts the transmit verdict instead of polling for ACK frames (which a hardware-ACK net core never forwards):

make -C examples/platform-specific/nrf/ipc-radio-service \
     TARGET=nrf BOARD=nrf5340/dk/network NRF_802154=1 ipc-radio-service.upload
make -C examples/rpl-udp TARGET=nrf BOARD=nrf5340/dk/application \
     NRF_802154=1 udp-server.upload

Design

Frame reception is fully interrupt-driven via the IPC MAC driver: the radio ISR triggers the radio driver process, which calls the IPC MAC’s input function to forward the frame to the app core via shared memory. Between events, the CPU sleeps (WFI), minimizing energy consumption and preventing bus stalls.

IPC commands from the app core are delivered via IPC interrupt. The service process wakes only when there is actual work to do.

UARTE is disabled on the network core (NRF_HAS_UARTE 0). All debug output is redirected to a shared memory ring buffer, which the application core drains and prints with a [NET] prefix.

TSCH is not supported — the IPC latency is too high for TSCH slot timing. Use CSMA (the default).

Running RPL UDP over IPC

First, flash the network core radio service (see above). The application core then automatically uses ipc_radio_driver to reach the radio, so any standard Contiki-NG application builds and runs unchanged. To flash the RPL UDP server on the application core:

make -C examples/rpl-udp TARGET=nrf BOARD=nrf5340/dk/application \
     udp-server.upload

On a second node (e.g., nRF52840 DK), flash the RPL UDP client:

make -C examples/rpl-udp TARGET=nrf BOARD=nrf52840/dk udp-client.upload

TrustZone Mode

To run the same example with the radio driver behind the TrustZone secure-world boundary, add TRUSTZONE=1 to the application build:

make -C examples/rpl-udp TARGET=nrf BOARD=nrf5340/dk/application \
     TRUSTZONE=1 udp-server.upload

This recursively builds the bundled secure world, links the normal world against its CMSE import library, merges both images, and flashes the merged hex. See ../trustzone/README.md for the full list of knobs (custom secure world, etc.) and for the manual build flow.