MCUXpresso

DART-MX8M - MCUXpresso 2.5.1

Overview

MCUXpresso SDK

MCUXpresso SDK board support provides example applications for NXP development and evaluation boards for Arm Cortex-M cores. Board support packages are found inside of the top level boards folder, and each supported board has its own folder (MCUXpresso SDK package can support multiple boards). Within each <board_name> folder there are various sub-folders to classify the type of examples they contain. These include (but are not limited to):

• cmsis_driver_examples: Simple applications intended to concisely illustrate how to use CMSIS drivers.
• demo_apps: Full-featured applications intended to highlight key functionality and use cases of the target MCU. These applications typically use multiple MCU peripherals and may leverage stacks and middleware.
• driver_examples: Simple applications intended to concisely illustrate how to use the MCUXpresso SDK’s peripheral drivers for a single use case.
• rtos_examples: Basic FreeRTOS OS examples showcasing the use of various RTOS objects (semaphores, queues, and so on) and interfacing with the MCUXpresso SDK’s RTOS drivers
• multicore_examples: Simple applications intended to concisely illustrate how to use middleware/multicore stack

Here we describe how to use ARM GCC toolchain, officially supported following Getting Started with MCUXpresso SDK i.MX 8M Devices.pdf.

Prerequisites

Before starting, prepare a Yocto boot SD (Sumo or newer).

To allow Cortex M4 accessing shared resources without experiencing Linux kernel conflicts, a dedicated device tree must be loaded, by selecting the right version with the symbolic link in the /boot folder of the booting media.
These device trees contain m4 label in their name.

The below table lists an example dtb blob file name for DART-MX8M (on DT8MCustomBoard rev. 1.3 and higher) with support for M4 (and SD card and LVDS), for each kernel version / Yocto release:

File Name	Description
imx8mq-var-dart-dt8mcustomboard-m4-sd-lvds.dtb	For kernel >= 5.4.85 (Yocto >= Dunfell)
imx8mq-var-dart-m4-sd-lvds.dtb	For kernel = 5.4.24 (Yocto Zeus)
fsl-imx8mq-var-dart-m4-sd-lvds.dtb	For kernel = 4.19.35 (Yocto Warrior)
Image.gz-fsl-imx8mq-var-dart-m4-sd-lvds.dtb	For kernel = 4.14.98 (Yocto Sumo)

For the full list of device tree blob files, refer to the "Build Results" section in the appropriate wiki page for the specific Yocto/Debian release you are using.

Installing required packages

Install cmake

sudo apt-get install cmake

Download and install GNU-ARM bare-metal toolchain:

mkdir ~/var-mcuxpresso
cd ~/var-mcuxpresso
wget https://developer.arm.com/-/media/Files/downloads/gnu-rm/7-2018q2/gcc-arm-none-eabi-7-2018-q2-update-linux.tar.bz2
tar xvf gcc-arm-none-eabi-7-2018-q2-update-linux.tar.bz2

Download MCUXpresso SDK for the SOM:

cd ~/var-mcuxpresso
git clone https://github.com/varigit/freertos-variscite -b mcuxpresso_sdk_2.5.x-var01
cd freertos-variscite

Documentation

Original NXP documentation is available online or in the following folder:

~/var-mcuxpresso/freertos-variscite/docs

Available demos

All of the Variscite examples are located under the following folder

~/var-mcuxpresso/freertos-variscite/boards/dart_mx8mq

Default M4 pins used by the demos are:

Function	Pin
debug UART (UART2)	RX: J12.6 / TX: J12.4
GPIO (GPIO4_IO03)	LED7 for DT8MCustomBoard 1.x U43.2 / R228 for DT8MCustomBoard >= 2.0 (Use Oscilloscope to observe output signal)
I2C (I2C3)	SCL: J12.18 / SDA: J12.20
PWM (PWM2)	J14.3

The available demos for DART-MX8M are:

• driver_examples/i2c/interrupt_b2b_transfer/slave
• driver_examples/i2c/interrupt_b2b_transfer/master
• driver_examples/i2c/polling_b2b_transfer/slave
• driver_examples/i2c/polling_b2b_transfer/master
• driver_examples/wdog
• driver_examples/gpio/led_output
• driver_examples/tmu/tmu_monitor_report
• driver_examples/pwm
• driver_examples/uart/auto_baudrate_detect
• driver_examples/uart/interrupt
• driver_examples/uart/interrupt_rb_transfer
• driver_examples/uart/polling
• driver_examples/uart/interrupt_transfer
• driver_examples/gpt/timer
• driver_examples/gpt/capture
• driver_examples/ecspi/ecspi_loopback
• driver_examples/qspi/polling_transfer
• driver_examples/rdc
• driver_examples/sema4/uboot
• rtos_examples/freertos_ecspi/ecspi_loopback
• rtos_examples/freertos_hello
• rtos_examples/freertos_queue
• rtos_examples/freertos_sem
• rtos_examples/freertos_generic
• rtos_examples/freertos_uart
• rtos_examples/freertos_tickless
• rtos_examples/freertos_mutex
• rtos_examples/freertos_event
• rtos_examples/freertos_swtimer
• rtos_examples/freertos_i2c
• cmsis_driver_examples/i2c/int_b2b_transfer/slave
• cmsis_driver_examples/i2c/int_b2b_transfer/master
• cmsis_driver_examples/uart/interrupt_transfer
• cmsis_driver_examples/ecspi/int_loopback_transfer
• multicore_examples/rpmsg_lite_str_echo_rtos
• multicore_examples/rpmsg_lite_pingpong_rtos/linux_remote
• demo_apps/hello_world

Almost all of the above demos are also available for EVK-MIMX8MQ.

You can build and run the demos following official NXP documentation for EVK-MIMX8MQ, available online or in the following document:

~/var-mcuxpresso/freertos-variscite/docs/Getting Started with MCUXpresso SDK i.MX 8M Devices.pdf

Building a demo

For any demo just follow this steps:

cd ~/var-mcuxpresso/freertos-variscite/boards/dart_mx8mq
cd <demo_folder>
cd armgcc
export ARMGCC_DIR=~/var-mcuxpresso/gcc-arm-none-eabi-7-2018-q2-update
./build_all.sh > /dev/null

You can choose any <demo_folder> from the list available in the previous section.

Then copy the ".bin" to the boot media (either the SD or eMMC) in the /boot folder already hosting the Linux device trees.

Memory types

The SDK allow linking using 2 different memory types: DDR, TCM.

Here is available a short summary of memory areas used by Cortex-M4 as described in related linker file.

memory type	M4 memory area	A53 memory area	memory lentgh	linker file
DDR	0x80000000-0x801FFFFF (code) 0x80200000-0x803FFFFF (data) 0x80400000-0x80FFFFFF (data2)	0x80000000-0x801FFFFF (code) 0x80200000-0x803FFFFF (data) 0x80400000-0x80FFFFFF (data2)	16MB (DDR)	MIMX8MQ6xxxJZ_cm4_ddr_ram.ld
TCM	0x1FFE0000-0x1FFFFFFF (code) 0x20000000-0x2001FFFF (data) 0x80000000-0x80FFFFFF (data2)	0x007E0000-0x007FFFFF (code) 0x00800000-0x0081FFFF (data) 0x80000000-0x80FFFFFF (data2)	256kB (TCM) + 16MB (DDR)	MIMX8MQ6xxxJZ_cm4_ram.ld

All linker files are locate in the armgcc folder of each demo.

The DDR reserved area must match the one declared in the kernel device tree: at least 2 GB of RAM is required on the SoM to allow Cortex-M4 accessing the range 0x80000000 - 0x80FFFFFF.

The RPMSG area is located at 0xB8000000: at least 3 GB of RAM is required on the SoM to allow Cortex-M4 accessing the RPMSG area. After launching the build_all.sh command the following folder will be created in the armgcc folder

• ddr_debug: containing DDR binaries compiled in debug mode (not stripped: symbols available)
• ddr_release: containing DDR binaries compiled in release mode (stripped: no symbols available)
• debug: containing TCM binaries compiled in debug mode (not stripped: symbols available)
• release: containing TCM binaries compiled in release mode (stripped: no symbols available)

Further details about memory mapping are available in the following i.MX 8M Applications Processor Reference Manual paragraphs:

• 2.1.2 Cortex-A53 Memory Map
• 2.1.3 Cortex-M4 Memory Map

Running a demo

To allow Cortex M4 accessing shared resources without experiencing Linux kernel conflicts, a dedicated device tree must be loaded.

To enable Cortex M4:

setenv use_m4 yes; saveenv

To disable Cortex M4:

setenv use_m4 no; saveenv

Binary demos must be loaded to the memory type used for linking.

To use TCM:

setenv m4_addr 0x7e0000; saveenv

To use DDR:

setenv m4_addr 0x7E000000; saveenv

To set the name of the M4 binary

setenv m4_bin myapp.bin; saveenv

The .bin file is expected in the folder /boot of the booting media.

The uboot boot command will take care to correctly load the M4 firmware and start Linux for DART-MX8M

Additional details and step by step procedure to run each of the demos is available online or in the following document:

~/var-mcuxpresso/freertos-variscite/docs/Getting Started with MCUXpresso SDK i.MX 8M Devices.pdf

Debugging a demo

JTAG interface

Cortex M4 debugging requires JTAG.

The VAR-DT8MCustomBoard exports the DART-MX8M JTAG signals through J29, a standard 1.27" 10 pin header.

Here is the pinout:

pin	signal	description	pin	signal	description
1	JTAG_VREF	JTAG IO reference voltage, connects to SOM_NVCC_3V3.	2	JTAG_TMS	JTAG Mode Select signal
3	GND	Digital Ground	4	JTAG_TCK	JTAG Clock signal, requires 10K pull down.
5	GND	Digital Ground	6	JTAG_TDO	JTAG Data Out signal
7	GND	Digital Ground	8	JTAG_TDI	JTAG Data In signal
9	JTAG_NTRST_C	JTAG Reset signal	10	NRST_CON	Programmer Reset, used to put the SOC in reset state.

Please refer to board schematics for further details.

Debugging GUI

A detailed step by step procedure to debug using SEGGER J-Link is available online or in the following document:

~/var-mcuxpresso/freertos-variscite/docs/Getting Started with MCUXpresso SDK i.MX 8M Devices.pdf