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Zephyr on the i.MX 8M Plus EVK Cortex-M7

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This guide builds a Zephyr RTOS firmware for the i.MX8MP's Cortex-M7 co-processor inside the Avocado SDK and runs it alongside Linux, with the two cores talking over rpmsg (OpenAMP).

Prerequisites​

  • Hardware: NXP i.MX 8M Plus EVK (imx8mp-evk) and boot media (SD card) for first-time provisioning.
  • Host: the Avocado CLI and Docker (the SDK runs in a container).
  • Network: the build fetches Zephyr sources via west, so the SDK container needs network access (already set with --network=host in avocado.yaml).
  • U-Boot access: a serial console to the EVK so you can set the boot devicetree (see Deploy).

Initialize​

git clone https://github.com/avocado-linux/references.git
cd references/zephyr-imx8mp-evk

default_target is imx8mp-evk, so no --target flag is needed.

Install​

avocado install

This resolves the runtime plus the SDK toolchain, including nativesdk-gcc-arm-none-eabi (the bare-metal ARM compiler used to build the M7 firmware).

Build​

avocado build

For this reference the build step, inside the SDK:

  1. west init/updates Zephyr at the revision pinned in zephyr-compile.sh.
  2. Cross-compiles the samples/subsys/ipc/openamp_rsc_table sample for imx8mp_evk/mimx8ml8/m7 with the gnuarmemb toolchain → zephyr.elf.
  3. Installs it into the zephyr-m7 extension at /usr/lib/firmware/zephyr_imx8mp_m7.elf.

To iterate on just the firmware: avocado sdk compile zephyr (and avocado sdk clean zephyr to wipe it).

Deploy​

First time (provision the board):

avocado provision -r dev

Write the image to your media and boot the EVK.

Boot the rpmsg devicetree (required for the M7 to come up). By default the EVK boots imx8mp-evk.dtb, which has no M7 node. From the U-Boot console, point fdtfile at the rpmsg devicetree shipped by the BSP:

setenv fdtfile imx8mp-evk-rpmsg.dtb
saveenv

Without this, /sys/class/remoteproc/remoteproc0 won't exist and the loader service no-ops by design.

Iterative updates (already provisioned + reachable):

avocado deploy -r dev -d <board-ip>

Verify​

After boot, confirm the firmware is present and the M7 is running:

ls -l /usr/lib/firmware/zephyr_imx8mp_m7.elf
systemctl status zephyr-m7-remoteproc.service
cat /sys/class/remoteproc/remoteproc0/state    # -> running

Confirm the A53 ↔ M7 rpmsg link:

ls /sys/bus/rpmsg/devices                       # rpmsg endpoint(s)
dmesg | grep -iE 'remoteproc|rpmsg|virtio'

The openamp_rsc_table sample echoes messages back over rpmsg; see the Zephyr sample docs for the matching Linux-side rpmsg test.

Customize​

Edit the pins at the top of zephyr-compile.sh:

  • ZEPHYR_MANIFEST_URL / ZEPHYR_REV — the manifest repo + revision. Swap for a fork (e.g. Nordic's nRF Connect SDK) or a different tag. Nothing in the distro is pinned to a Zephyr release.
  • ZEPHYR_BOARD / ZEPHYR_SAMPLE — the board name and sample path track Zephyr's hardware-model-v2 layout; adjust if you pin an older Zephyr (e.g. board named mimx8mp_evk_m7).

The same bare-metal toolchain builds FreeRTOS, STM32Cube, or plain bare-metal firmware just as well — point the compile hook at your source and rebuild.