inav/docs/SITL/SITL.md

SITL

ATTENTION!

SITL is currently still under development.

SITL (Software in the loop) allows to run INAV completely in software on the PC without using a flight controller and simulate complete FPV flights. For this, INAV is compiled with a normal PC compiler.

The sensors are replaced by data provided by a simulator. Currently supported are

• RealFlight https://www.realflight.com/
• X-Plane https://www.x-plane.com/
• fl2sim replay Blackbox Log via SITL, uses the X-Plane protocol.

INAV SITL communicates for sensor data and control directly with the corresponding simulator, see the documentation of the individual simulators and the Configurator or the command line options.

Sensors

The following sensors are emulated:

• IMU (Gyro, Accelerometer)
• GPS
• Pitot
• Magnetometer (Compass)
• Rangefinder
• Barometer
• Battery (current and voltage), depending on simulator

Select "FAKE" as type for all mentioned, so that they receive the data from the simulator.

Serial ports+

UARTs are replaced by TCP starting with port 5760 ascending. UART 1 port 5760, UART2 5761, ... By default, UART1 and UART2 are available as MSP connections. Other UARTs will have TCP listeners if they have an INAV function assigned. To connect the Configurator to SITL: Select TCP and connect to localhost:5760 (or 127.0.0.1:5760 if your OS doesn't understand localhost) (if SITL is running on the same machine). IPv4 and IPv6 are supported, either raw addresses or host-name lookup.

The assignment and status of user UART/TCP connections is displayed on the console.

INAV 6.1.0 SITL
[SYSTEM] Init...
[SIM] No interface specified. Configurator only.
[EEPROM] Loaded 'eeprom.bin' (32768 of 32768 bytes)
[SOCKET] Bind TCP :: port 5760 to UART1
[SOCKET] Bind TCP :: port 5761 to UART2
[SOCKET] ::1 connected to UART1

All other interfaces (I2C, SPI, etc.) are not emulated.

Remote control

MSP_RX (TCP/IP) or joystick (via simulator) or serial receiver via USB/Serial interface are supported.

MSP_RX

MSP_RX is the default, 18 channels are supported over TCP/IP serial emulation.

Joystick interface

Only 8 channels are supported. Select "SIM (SITL)" as the receiver and set up a joystick in the simulator, details of which can be found in the documentation for the individual simulators.

Serial Receiver via USB

Connect a serial receiver (e.g. SBUS) to the PC via a UART/USB adapter. Configure the receiver in the Configurator as usual.

The Configurator offers a built-in option for forwarding the serial data to the SITL TCP port, if SITL is started manually the following option can be used:

The connection can then be established with a programme that forwards the serial data unaltered to TCP, e.g. with the Python script tcp_serial_redirect.py (https://github.com/Scavanger/TCP-Serial-Redirect) If necessary, please download the required runtime environment from https://www.python.org/. Please use the linked version, which has a smaller buffer, otherwise the control response is relatively slow.

Example SBUS:

For this you need a FT232 module. With FT-Prog (https://ftdichip.com/utilities/) the signals can be inverted: Devices->Scan and Parse, then Hardware Specific -> Invert RS232 Signals -> Invert RXD.

For SBUS, the command line arguments of the python script are: python tcp_serial_redirect.py --parity E --stopbits 2 -c 127.0.0.1:[INAV-UART-PORT] COMXX 100000

Telemetry

LTM and MAVLink telemetry are supported, either as a discrete function or shared with MSP.

RX Telemetry via a return channel through the receiver is not yet supported by SITL.

OSD

For the OSD the program INAV-Sim-OSD is available: https://github.com/Scavanger/INAV-SIM-OSD. For this, activate MSP-Displayport on a UART/TCP port and connect to the corresponding port.

Note: INAV-Sim-OSD only works if the simulator is in window mode.

Command line

The command line options are only necessary if the SITL executable is started by hand.

There is also a SITL tab in the INAV Configurator (6.1.0 and later).

The following SITL specific command line options are available:

If SITL is started without command line options, only a serial MSP / CLI connection can be used (e.g. Configurator or other application) can be used.

--path Path and file name to config file. If not present, eeprom.bin in the current directory is used. Example: C:\INAV_SITL\flying-wing.bin, /home/user/sitl-eeproms/test-eeprom.bin.

--sim=[sim] Select the simulator. xp = X-Plane, rf = RealFlight. Example: --sim=xp

--simip=[ip] Hostname or IP address of the simulator, if you specify a simulator with "--sim" and omit this option IPv4 localhost (127.0.0.1) will be used. Example: --simip=172.65.21.15, --simip acme-sims.org, --sim ::1.

--simport=[port] Port number of the simulator, not necessary for all simulators. Example: --simport=4900. For the X-Plane protocol, the default port is 49000.

--useimu Use IMU sensor data from the simulator instead of using attitude data directly from the simulator. Not recommended, use only for debugging.

--chanmap=[chanmap] The channelmap to map the motor and servo outputs from INAV to the virtual receiver channel or control surfaces around simulator. Syntax: (M(otor)|S(ervo)-<RECEIVER_OUT>),..., all numbers must have two digits. Example: To assign motor1 to virtual receiver channel 1, servo 1 to channel 2, and servo2 to channel 3: --chanmap:M01-01,S01-02,S02-03 Please also read the documentation of the individual simulators.

--help Displays help for the command line options.

For options that take an argument, either form --flag=value or --flag value may be used.

Running SITL

It is recommended to start the tools in the following order:

1. Simulator, aircraft should be ready for take-off
2. INAV-SITL
3. OSD
4. serial redirect for RC input

Compile

Linux and FreeBSD:

Almost like normal, ruby, cmake and make are also required. With cmake, the option "-DSITL=ON" must be specified.

mkdir build_SITL
cd build_SITL
cmake -DSITL=ON ..
make

Windows:

Compile under cygwin, then as in Linux. Copy cygwin1.dll into the directory, or include cygwin's /bin/ directory in the environment variable PATH.

If the build fails (segfault, possibly out of memory), adding -DCMAKE_BUILD_TYPE=MinRelSize to the cmake command may help.

Build manager

ninja may also be used (parallel builds without -j $(nproc)):

cmake -GNinja -DSITL=ON ..
ninja

Compiler requirements

• Modern GCC. Must be a real GCC, macOS faking it with clang will not work. GCC 10 to GCC 13 are known to work.
• Unix sockets networking. Cygwin is required on Windows (vice winsock).
• Pthreads

Supported environments

• Linux on x86_64, ia-32, Aarch64 (e.g. Rpi4), RISCV64 (e.g. VisionFive2)
• Windows on x86_64
• FreeBSD (x86_64 at least).