i.MX8MM EVK

Overview

i.MX8M Mini LPDDR4 EVK board is based on NXP i.MX8M Mini applications processor, composed of a quad Cortex®-A53 cluster and a single Cortex®-M4 core. Zephyr OS is ported to run on the Cortex®-A53 core.

Board features:
- RAM: 2GB LPDDR4
- Storage:
  - SanDisk 16GB eMMC5.1
  - Micron 32MB QSPI NOR
  - microSD Socket
- Wireless:
  - WiFi: 2.4/5GHz IEEE 802.11b/g/n
  - Bluetooth: v4.1
- USB:
  - OTG - 2x type C
- Ethernet
- PCI-E M.2
- Connectors:
  - 40-Pin Dual Row Header
- LEDs:
  - 1x Power status LED
  - 1x UART LED
- Debug
  - JTAG 20-pin connector
  - MicroUSB for UART debug, two COM ports for A53 and M4

More information about the board can be found at the NXP website.

Supported Features

The Zephyr imx8mm_evk board for Cortex-A53 configuration supports the following hardware features:

Interface	Controller	Driver/Component
GIC-v3	on-chip	interrupt controller
ARM TIMER	on-chip	system clock
CLOCK	on-chip	clock_control
PINMUX	on-chip	pinmux
RDC	on-chip	Resource Domain Controller
UART	on-chip	serial port
GPT	on-chip	timer
ENET	on-chip	ethernet port

The Zephyr imx8mm_evk board for Cortex-M4 supports the following hardware features:

Interface	Controller	Driver/Component
NVIC	on-chip	nested vector interrupt controller
SYSTICK	on-chip	systick
CLOCK	on-chip	clock_control
PINMUX	on-chip	pinmux
UART	on-chip	serial port-polling; serial port-interrupt
GPIO	on-chip	GPIO output GPIO input

The default configuration can be found in the defconfig file: boards/nxp/imx8mm_evk/imx8mm_evk_mimx8mm6_m4_defconfig

It is recommended to disable peripherals used by the M4 core on the Linux host.

Other hardware features are not currently supported by the port.

Devices

System Clock

This board configuration uses a system clock frequency of 8 MHz.

The M4 Core is configured to run at a 400 MHz clock speed.

Serial Port

This board configuration uses a single serial communication channel with the CPU’s UART4. This is used for the M4 and A53 core targets.

Programming and Debugging (A53)

U-Boot “cpu” command is used to load and kick Zephyr to Cortex-A secondary Core, Currently it is supported in : Real-Time Edge U-Boot (use the branch “uboot_vxxxx.xx-y.y.y, xxxx.xx is uboot version and y.y.y is Real-Time Edge Software version, for example “uboot_v2023.04-2.9.0” branch is U-Boot v2023.04 used in Real-Time Edge Software release v2.9.0), and pre-build images and user guide can be found at Real-Time Edge Software.

Copy the compiled zephyr.bin to the first FAT partition of the SD card and plug the SD card into the board. Power it up and stop the u-boot execution at prompt.

Use U-Boot to load and kick zephyr.bin to Cortex-A53 Core0:

fatload mmc 1:1 0x93c00000 zephyr.bin; dcache flush; icache flush; go 0x93c00000

Or kick zephyr.bin to the other Cortex-A53 Core, for example Core2:

fatload mmc 1:1 0x93c00000 zephyr.bin; dcache flush; icache flush; cpu 2 release 0x93c00000

Use this configuration to run basic Zephyr applications and kernel tests, for example, with the Basic Synchronization sample:

# From the root of the zephyr repository
west build -b imx8mm_evk/mimx8mm6/a53 samples/synchronization
west build -t run

This will build an image with the synchronization sample app, boot it and display the following ram console output:

*** Booting Zephyr OS build zephyr-v3.1.0-3575-g44dd713bd883  ***
thread_a: Hello World from cpu 0 on mimx8mm_evk_a53!
thread_b: Hello World from cpu 0 on mimx8mm_evk_a53!
thread_a: Hello World from cpu 0 on mimx8mm_evk_a53!
thread_b: Hello World from cpu 0 on mimx8mm_evk_a53!
thread_a: Hello World from cpu 0 on mimx8mm_evk_a53!

Use Jailhouse hypervisor, after root cell linux is up:

#jailhouse enable imx8mm.cell
#jailhouse cell create imx8mm-zephyr.cell
#jailhouse cell load 1 zephyr.bin -a 0x93c00000
#jailhouse cell start 1

Programming and Debugging (M4)

The MIMX8MM EVK board doesn’t have QSPI flash for the M4 and it needs to be started by the A53 core. The A53 core is responsible to load the M4 binary application into the RAM, put the M4 in reset, set the M4 Program Counter and Stack Pointer, and get the M4 out of reset. The A53 can perform these steps at bootloader level or after the Linux system has booted.

The M4 can use up to 3 different RAMs. These are the memory mapping for A53 and M4:

Region	Cortex-A53	Cortex-M4 (System Bus)	Cortex-M4 (Code Bus)	Size
OCRAM	0x00900000-0x0093FFFF	0x20200000-0x2023FFFF	0x00900000-0x0093FFFF	256KB
TCMU	0x00800000-0x0081FFFF	0x20000000-0x2001FFFF		128KB
TCML	0x007E0000-0x007FFFFF		0x1FFE0000-0x1FFFFFFF	128KB
OCRAM_S	0x00180000-0x00187FFF	0x20180000-0x20187FFF	0x00180000-0x00187FFF	32KB

For more information about memory mapping see the i.MX 8M Applications Processor Reference Manual (section 2.1.2 and 2.1.3)

At compilation time you have to choose which RAM will be used. This configuration is done in the file boards/nxp/imx8mm_evk/imx8mm_evk_mimx8mm6_m4.dts with “zephyr,flash” (when CONFIG_XIP=y) and “zephyr,sram” properties. The available configurations are:

"zephyr,flash"
- &tcml_code
- &ocram_code
- &ocram_s_code

"zephyr,sram"
- &tcmu_sys
- &ocram_sys
- &ocram_s_sys

Load and run Zephyr on M4 from A53 using u-boot by copying the compiled zephyr.bin to the first FAT partition of the SD card and plug the SD card into the board. Power it up and stop the u-boot execution at prompt.

Load the M4 binary onto the desired memory and start its execution using:

fatload mmc 0:1 0x7e0000 zephyr.bin;bootaux 0x7e0000

Debugging

MIMX8MM EVK board can be debugged by connecting an external JLink JTAG debugger to the J902 debug connector and to the PC. Then the application can be debugged using the usual way.

Here is an example for the Hello World application.

# From the root of the zephyr repository
west build -b imx8mm_evk/mimx8mm6/m4 samples/hello_world
west debug

Open a serial terminal, step through the application in your debugger, and you should see the following message in the terminal:

***** Booting Zephyr OS build zephyr-v2.0.0-1859-g292afe8533c0 *****
Hello World! imx8mm_evk