VAR-SOM-MX8M-NANO - Yocto Programming with Visual Studio Code

Visual Studio Code (VSCode) is a powerful, modern code editor that can be used to develop and debug C/C++ applications on Variscite System on Modules.

This guide demonstrates how to create and debug a C++ application using VSCode on the VAR-SOM-MX8M-NANO.

Setup Host Computer Environment

Please follow the steps below to prepare a fresh Ubuntu 20.04 installation for VSCode debugging:

Install Dependencies

$ sudo apt-get -y update
$ sudo apt-get -y install build-essential gdb gdb-multiarch git

Install VSCode

$ sudo snap install --classic code

Install VSCode Extensions

VSCode 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 required extensions using the command line:

$ code --install-extension ms-vscode.cpptools

Install Yocto Toolchain

A toolchain is necessary for cross compiling applications. To install the toolchain, follow Variscite's Yocto Toolchain installation guide.

Create, cross compile, and run a new "Hello, World!" project

First, open a new terminal and configure the environment with the toolchain setup script:

$ source /opt/fsl-imx-xwayland/5.4-zeus/environment-setup-aarch64-poky-linux

From the same terminal, create an empty project directory and open VSCode:

$ mkdir ~/var-hello-world
$ cd ~/var-hello-world
$ code .

Create a new file called main.cpp:

main.cpp:

#include <stdio.h>

int main(int argc, char *argv[]) {
    printf("Hello, World!\n");
    return 0;
}

Create a new Makefile to build hello.bin

Makefile:

all: main.cpp
	$(CXX) $(CXXFLAGS) -O0 main.cpp -g -o hello.bin
clean:
	rm -f hello.bin

Open a new terminal in VSCode by typing ctrl+shift+`. Your workspace should look similar to this:

Run make in the new terminal

$ make

Send hello.bin to the target device using SCP:

$ scp hello.bin root@<ip addr>:/home/root/

Launch hello.bin on the target device:

# ./hello.bin 
Hello, World!

Remote Debugging with VSCode

After verifying hello.bin runs on the target device, we can now setup VSCode for remote debugging.

The working directory should currently have these files:

~/var-hello-world$ find
.
./Makefile
./main.cpp

We will add three files to the project:

var-build-and-debug.sh	Generic script to build, deploy, and launch gdbserver
.vscode/launch.json	VSCode file to configure debug settings. Runs `var-build-and-debug` in tasks.json
.vscode/tasks.json	VSCode file to override or add new tasks. Calls `var-debug-and-debug.sh` prior to debugging.

Create var-build-and-debug.sh

First, add a generic script to build, deploy, and launch gdbserver. The script requires two arguments:

TARGET_IP: The IP Address of the target device
PROGRAM: The name of the binary executable, hello.bin in this example

In the end, tasks.json will run this script at the beginning of each debug session.

var-build-and-debug.sh:

#!/bin/bash
readonly TARGET_IP="$1"
readonly PROGRAM="$2"
readonly TARGET_DIR="/home/root"

# rebuild project
make clean; make -j$(nproc)

# kill gdbserver on target
ssh root@${TARGET_IP} "sh -c '/usr/bin/killall -q gdbserver; exit 0'"

# send the program to the target
scp ${PROGRAM} root@${TARGET_IP}:${TARGET_DIR}

# start gdbserver on target
REMOTE_GDB_CMD="ssh -t root@${TARGET_IP} \"sh -c 'cd ${TARGET_DIR}; gdbserver localhost:3000 ${PROGRAM}'\""
gnome-terminal -x bash -c "${REMOTE_GDB_CMD}"

Create launch.json

VSCode has a powerful built in debugger capable of debugging many programming languages. In this step, we will add a configuration for debugging CPP:

.vscode/launch.json:

{
    "version": "0.2.0",
    "configurations": [{
        "name": "GDB debug",
        "type": "cppdbg",
        "request": "launch",
        "program": "hello.bin",
        "args": [],
        "stopAtEntry": true,
        "cwd": "${workspaceFolder}",
        "environment": [],
        "console": "integratedTerminal",
        "MIMode": "gdb",
        "targetArchitecture": "arm64",
        "preLaunchTask": "var-build-and-debug",
        "setupCommands": [{
            "description": "Enable pretty-printing for gdb",
            "text": "-enable-pretty-printing",
            "ignoreFailures": true
        }],
        "miDebuggerPath": "/usr/bin/gdb-multiarch",
        "miDebuggerServerAddress": "192.168.0.118:3000",
    }]
}

See the table below for important details regarding launch.json variables:

`miDebuggerServerAddress`	Must match the IP Address of the target device
`program`	Must match the name of the binary generated by the the Makefile
`preLaunchTask`	Must match the name of the task in `.vscode/tasks.json` in the following step

Create tasks.json

In launch.json, we created a preLaunchTask to run a task named var-build-and-debug at the beginning of each debugging session. This task is configured by adding a .vscode/tasks.json file:

.vscode/tasks.json:

{
    "version": "2.0.0",
    "tasks": [{
        "label": "var-build-and-debug",
        "type": "shell",
        "command": "sh",
        "args": [
            "var-build-and-debug.sh",
            "192.168.0.118",
            "hello.bin"
        ],
    }
}

The following table summarizes variables in tasks.json:

`label`	Must match preLaunchTask in launch.json
`type`	This task will launch a shell
`command`	Launch sh, with arguments `var-build-and-debug.sh "192.168.0.136" "hello.bin"`

Note: The IP Address must match the IP address of the target device, as defined in .vscode/launch.json

Launch a Debugging Session

After following the steps above, the working directory should now have these files:

~/var-hello-world$ find
.
./.vscode
./.vscode/launch.json
./.vscode/tasks.json
./Makefile
./var-build-and-debug.sh
./main.cpp
./hello.bin

A new debugging session can be started by typing 'f5' on the keyboard. Please click on the image below for a real time debugging demonstration:

Example Project Source Code

The source code for this example is available from Variscite's Github repository:

$ git clone https://github.com/nsdrude-varigit/var-demos
$ cd var-demos/hello-world

Setup the toolchain environment:

$ source /opt/fsl-imx-xwayland/5.4-zeus/environment-setup-aarch64-poky-linux

Launch VSCode:

$ code .

Configure the target device IP Address in .vscode/tasks.json and .vscode/launch.json

Finally, start a debugging session by typing 'f5' on the keyboard

Yocto Programming with VSCode

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