Sming Host Emulator


Allows Sming applications to be built as an executable to run on the development host (Windows or Linux).

This is a source-level emulator for developing and testing new framework code prior to flashing a real device.

This is not a machine emulator; if you need something operating at a lower level take a look at QEMU.


CMake is required to build LWIP

Ensure you are using relatively recent compilers, with 32-bit libraries available.

For Linux, you may require the gcc-multilib and g++-multilib packages to build 32-bit executables on a 64-bit OS.

For Windows, make sure your MinGW distro is up to date. See Manual Windows Installation for further details.


Build the framework and application as usual, specifying SMING_ARCH =Host. For example:

make SMING_ARCH=Host
cd $SMING_HOME/../samples/Basic_Serial
make SMING_ARCH=Host

This builds the application as an executable in, for example, out/Host/firmware/app.exe. Various command-line options are supported, use --help for details.

The easiest way to run the emulator is via make run. Variables are used to pass the appropriate options (see features).

To find out what options are in force, use make list-config.


Flash memory

This is emulated using a backing file. By default it’s in flash.bin in the firmware directory, you can change it by setting FLASH_BIN. The size of the flash memory is set via SPI_SIZE.

  • make flashinit to clear and reset the file.
  • make flashfs to copy the generated SPIFFS image into the backing file.
  • make flash writes out all required images to the backing file. For now, this is the same as make flashfs but that will change when support is added for custom user images.

UART (serial) ports

Multiple serial terminals are supported via raw TCP network sockets, so telnet can be used to provide terminal capability.

make run starts the emulator with any required telnet sessions. By default, no serial ports are enabled, however any output from UART0 is redirected to the console. No input is possible.

If your project requires proper terminal access, set ENABLE_HOST_UARTID.

Set HOST_UART_PORTBASE if you want to change the base port number used to communicate with the emulator.

Alternatively, you can run the application manually like this:

out/Host/debug/firmware/app --pause --uart=0 --uart=1

Now start a telnet session for each serial port, in separate command windows:

telnet localhost 10000
telnet localhost 10001

In the application window, press Enter. This behaviour is enabled by the pause option, which stops the emulator after initialisation so telnet can connect to it. Without pause you’ll lose any serial output at startup.)

Note: For Windows users, putty is a good alternative to telnet. It also has options for things like carriage-return/linefeed translation (“\n” -> “\r\n`”). Run using:

putty telnet://localhost:10000

Port numbers are allocated sequentially from 10000. If you want to use different port numbers, use --uartport option.

Digital I/O

By default, the emulator just writes output to the console so you can see when outputs are changed.

Reading from an input returns 0.

All digital functions can be customised by overriding the DigitalHooks class, like this:

// You'd probably put this in a separate module and conditionally include it
#ifdef ARCH_HOST
class MyDigitalHooks: public DigitalHooks
   // Override class methods as required
   uint8_t digitalRead(uint16_t pin, uint8_t mode) override
      if(pin == 0) {
         return 255;
      } else {
         return DigitalHooks::digitalRead(pin, mode);

MyDigitalHooks myDigitalHooks;

void init()
   #ifdef ARCH_HOST

See Sming/Arch/Host/Core/DigitalHooks.h for further details.



Network support is enabled by default. If you don’t need it, use the --nonet option.


Support is provided via TAP network interface (a virtual network layer operating at the ethernet frame level). A TAP interface must be created first, and requires root priviledge:

sudo ip tuntap add dev tap0 mode tap user `whoami`
sudo ip a a dev tap0
sudo ifconfig tap0 up

This creates the tap0 interface. The emulator will automatically select the first tap interface found. To override this, use the --ifname option. An IP address will be assigned, but can be changed using the --ipaddr option.

If your application needs to access the internet, additional setup is required:

sudo sysctl net.ipv4.ip_forward=1
sudo sysctl net.ipv6.conf.default.forwarding=1
sudo sysctl net.ipv6.conf.all.forwarding=1

export INTERNET_IF=wlan0 # <!--- Make sure to replace wlan0 with the network interface connected to Internet

sudo iptables -t nat -A POSTROUTING -o $INTERNET_IF -j MASQUERADE
sudo iptables -A FORWARD -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
sudo iptables -A FORWARD -i tap0 -o $INTERNET_IF -j ACCEPT


Requires NPCAP library to be installed. Provided with current (3.0.2) version of Wireshark.

By default, the first valid network adapter will be used, with address assigned via DHCP.

If the adapter is wrong, get a list thus:

out\Host\Windows\debug\firmware\app --ifname=?


make run HOST_NETWORK_OPTIONS=--ifname=?

produces a listing:

Available adapters:
- 0: {ACC6BFB2-A15B-4CF8-B93A-8D97644D0AAC} - Oracle /
- 1: {A12D4DD0-0EA8-435D-985E-A1F96F781EF0} - NdisWan Adapter
- 2: {3D66A354-39DD-4C6A-B9C4-14EE223FC3D1} - MS NDIS 6.0 LoopBack Driver /
- 3: {BC53D919-339E-4D70-8573-9D7A8AE303C7} - NdisWan Adapter
- 4: {3CFD43EA-9CC7-44A7-83D4-EB04DD029FE7} - NdisWan Adapter
- 5: {530640FF-A9C3-436B-9EA2-65102C788119} - Realtek PCIe GBE Family Controller /
- 6: {0F649280-BAC2-4515-9CE3-F7DFBB6A1BF8} - Kaspersky Security Data Escort Adapter /

Then use the appropriate number (or GUID), with the gateway IP address - an address will be assigned via DHCP:

make run HOST_NETWORK_OPTIONS="--ifname=5 --gateway="

You can find gateway addresses using the ipconfig command.

If you want to use a specific IP address, the appropriate adapter will be selected but you still need to specify the gateway address:

make run HOST_NETWORK_OPTIONS="--ipaddr= --gateway="


  • Add passthrough support for real serial ports to permit connection of physical devices.
  • Consider how this mechanism might be used to support emulation of other devices (SPI, I2C, etc).
  • Development platforms with SPI or I2C (e.g. Raspberry Pi) could be supported.
  • Are there any generic device emulators available? For example, to simulate specific types of SPI slave.