Building under Windows is generally slower than in Linux. This is because the current build system requires a Posix emulation layer (MinGW). However, it does offer the simplest way to use Sming on a Windows PC and does not affect the quality or functionality of your applications.

There are situations where it is highly desirable to build Sming in a Linux environment:

  • Making use of linux-only development tools, e.g. valgrind (dynamic bug detection system)

  • Integration building/testing prior to submitting a PR to the Sming repository

  • Need/want faster builds

Whilst a Windows computer can be configured to dual-boot with Linux, this is generally inconvenient for day-to-day use. A better solution is to run Linux inside a virtual machine environment such as VirtualBox, VmWare or Hyper-V.

Note that Docker is not a virtual environment but can in fact be run inside a virtual machine to take advantage of the process isolation and security benefits.

Windows Subsystem for Linux

“The Windows Subsystem for Linux lets developers run a GNU/Linux environment – including most command-line tools, utilities, and applications – directly on Windows, unmodified, without the overhead of a traditional virtual machine or dual-boot setup.”

There are currently two versions of WSL: this documentation relates to WSL2.


WSL2 uses Hyper-V so may conflict with other virtual machines you may be using.

Installing WSL

See instructions here

Install an up-to-date Linux distribution from the Microsoft store, currently Ubuntu-20.04.


You may encounter an error message similar to this during installation:

WslRegisterDistribution failed with error: 0x80370102
Error: 0x80370102 The virtual machine could not be started because a required feature is not installed.

One thing not mentioned in the instructions is to check that the hypervisor is set to auto-start at system boot. This is the default but for various reasons it can get disabled.

To check, type:


At an administrative command prompt. Under the Windows Boot Loader entry you should see an entry like this:

hypervisorlaunchtype    Auto

If it’s missing or set to another value (e.g. off) then change it as follows:

bcdedit /set {current} hypervisorlaunchtype auto

After a system reboot you should be able to continue with the installation.

Installing Sming

Open a WSL command prompt and follow the instructions in Linux Installation.

Please note:

  • A native Windows python3 distribution is required to enable access to serial ports.

  • Ensure that python is available in the system path for both WSL2 and Windows.

  • Do not set the PYTHON environment variable.

This will ensure that the build system can run python scripts either in WSL2 or in Windows as necessary.

Flashing devices

WSL2 does not currently support access to USB serial devices, so the Sming build system runs the appropriate application directly under Windows using powershell.exe.

Therefore, use the normal Windows COM port name rather than the linux ones (such as /dev/ttyUSB0):

make flash COM_PORT=COM4

Serial debugging

Again, as we have no direct access to USB COM ports a workaround is required. A small python application can be run on Windows to act as a simple bridge between the serial port and a TCP port. See Tools/ - run without arguments to see available options.

You can start the server like this:

make tcp-serial-redirect

A new console will be created (minimised) showing something like this:

--- TCP/IP to Serial redirect on COM4  115200,8,N,1 ---
--- type Ctrl-C / BREAK to quit
Waiting for connection on

This uses the current COM_PORT and COM_SPEED_SERIAL settings.

Now we can start the debugger:

make gdb COM_PORT_GDB=


You may get an error running make valgrind advising that libc6-dbg:i386 be installed. Here’s how:

sudo dpkg --add-architecture i386
sudo apt-get update
sudo apt-get install libc6-dbg:i386