VAR-SOM-MX8M-NANO - MCUXpresso 2.15.0 Development using MCUXpresso for VS Code extension

Overview

This guide demonstrates how to develop, cross compile and debug applications for the VAR-SOM-MX8M-NANO Cortex-m7 co-processor using NXP’s MCUXpresso for Visual Code extension.

Please visit Variscite's MCUXpresso Guide for additional information about manually building demos, integration with Yocto, running applications from U-Boot and Linux, and JTAG debugging.

Hardware

JTAG Debbugger: J-Link PLUS: https://www.segger.com/products/debug-probes/j-link/models/j-link-plus/
ARM-JTAG-20-10 adapter: https://www.digikey.it/it/products/detail/olimex-ltd/ARM-JTAG-20-10/3471401
Variscite Board: Symphony

Host Computer Environment Setup

Follow the steps below to prepare a fresh Ubuntu 22.04 installation for using the extension.

Note: cmake 3.20.5 is the required minimum version supported by MCUXpresso for VS Code extension and it is not supported by older Ubuntu versions.

Install Dependencies

$ sudo apt-get -y update
$ sudo apt-get -y install pip git

In order to access serial debugging ports your user must be in the ‘dialout’ group. To check this type:

$ groups

The above command will print all group memberships of the current user. If ‘dialout’ it is not printed, add your user to it:

$ sudo usermod -a -G dialout $USER

and restart your computer.

Download MCUXpresso SDK for the SOM:

$ mkdir -p ~/var-mcuxpresso/mcuxpresso-examples
$ cd ~/var-mcuxpresso
$ git clone https://github.com/varigit/freertos-variscite -b mcuxpresso_sdk_2.15.x-var01

Install VS Code

$ sudo snap install --classic code

Install MCUXpresso for VS Code Extension

VS Code has a graphical interface for installing and managing extensions. To learn more, please see Using extensions in Visual Studio Code

For this guide, we will install the MCUXpresso for VS Code extension:

Install MCUXpresso Dependencies

In the extension ‘Welcome' tab, click on ‘Check Tool Dependencies’, ‘Open Installer’ and then, on the bottom right notification, 'Download’:

Once the download finishes, the MCUXpresso Installer window will be displayed, showing multiple tools to install. For this guide we will install the following:

MCUXpresso SDK Developer;
SEGGER J-Link;
Arm GNU Toolchain;
Standalone Toolchain Add-ons.

Open a Demo in VS Code

After the dependencies are installed, close the MCUXpresso Installer and click on ‘Import Software Repositories’:

Go to the 'Local' tab, browse the previously git-cloned repository and import it:

Click on ‘Import Example from Repository’:

Select the previously imported repository, the Arm GNU Toolchain (the Toolchain version might differ), the VAR-SOM-MX8M-NANO board and the hello world demo. Use the previously created 'mcuxpresso-examples' directory for the 'Location':

Click on 'Explorer' on the left upper corner to open the project source code:

Build Demo using VS Code

To build the project click on extension icon on the left and on 'Build Selected':

If the build task completes successfully, a similar output as below should be generated:

Please visit Variscite's MCUXpresso Guide for instructions to run the demo using U-Boot or the Linux Remote Processor Framework.

Debugging with VS Code

Test Enviroment

Connect Hardware

Connect J-Link PLUS to JTAG connector of Variscite board
Connect J-Link PLUS to Development PC via USB cable

Load dedicated device tree

Please visit Variscite's MCUXpresso Guide for instructions to load a dedicated device tree.

For this example we will use imx8mn-var-som-symphony-m7.dtb:

From U-Boot

 => setenv fdt_file imx8mn-var-som-symphony-m7.dtb 
 => saveenv
 Saving Environment to MMC... Writing to MMC(1)... OK
 Power off / Power on the board

Or, from Linux

 $ fw_setenv fdt_file imx8mn-var-som-symphony-m7.dtb 
 $ reboot

Start Debugging

Make sure the Debug Probe is correctly identified by the extension:

If it is not, check your connections and restart VS Code.

Open source code and add a breakpoint:

Open the serial debugging port by clicking ‘View' → ‘Output’ → ‘…’ → 'Serial Monitor’:

Debug RPMSG demos

The RPMSG demos can be debugged only starting from U-Boot.
You need even to change M4 Kernel Device Tree enabling rpmsg node and disabling cortex-m node.

Change M4 Kernel Device Tree

Edit arch/arm64/boot/dts/freescale/imx8mn-var-som-symphony-m7.dtsi

imx8mm-cm4 {
    ...
    ...
    status = "disabled";
};

&rpmsg {
    ...
    ...
    status = "okay";
};

Save the changes.
Compile the device tree and update the SD card/eMMC.

Note: If rpmsg node is missing in the arch/arm64/boot/dts/freescale/imx8mn-var-som-symphony-m7.dtsi file discard the Change M4 Kernel Device Tree section above

For this example, we will debug pingpong demo mapped in DDR.

$ cd ~/var-mcuxpresso/freertos-variscite
$ ./var_add_vscode_support.sh -b som_mx8mn -e boards/som_mx8mn/multicore_examples/rpmsg_lite_pingpong_rtos/linux_remote -t ddr -d /opt/SEGGER/JLink
$ code ~/var-mcuxpresso/freertos-variscite/boards/som_mx8mn/multicore_examples/rpmsg_lite_pingpong_rtos/linux_remote/

Note: Debugging applications mapped in the DDR, the use of SDK_DelayAtLeastUs function is not recommended because it produces a long delay time.

You can use vTaskDelay() instead.

Build application following the guide at the Build Demo using VS Code section above:

Power on the Board and interrupt the boot in the U-Boot prompt.
From Visual Studio Code start Debugging.
From U-Boot prompt:

=> boot

Waiting for completed boot kernel
From Userspace prompt:

$ sysctl kernel.printk=7
$ modprobe imx_rpmsg_pingpong

If everything worked well the program will stop at the configured breakpoint:

Note: Debugging RPMSG demos be careful to set breakpoint or debug step by step because when the M core is stopped even A core is blocked

MCUXpresso VSCode extension

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