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SCons Build Script Generator

lbuild module: modm:build:scons

SCons is a software construction build system written in Python. For a better embedded experience, we've extended it with modm-specific build tools.

This module generates two files:

  • a modm/SConscript file: configures all required SCons tools with the right settings (also using information from the modm:build module) to compile the modm library.
  • a top-level BSD-licensed SConstruct file: configures additional, optional tools and sets up all the relevant SCons functions for your target.

The SConscript file is self contained and does not depend on anything outside of the modm/ directory. This allows it to be combined with SConscript of other projects without clashing.

In fact, if you look at your generated SConstruct file, you'll notice that it doesn't contain a lot of logic or specific data, it is only meant for calling the right SCons tool with the right arguments.

We do not intend to serve every possible use-case with this module. If you need something special, write your own SConstruct file, maybe starting by modifying ours. It is intentionally BSD-licensed so that you do not have to publish your changes to it.

Remember to set modm:build:scons:include_sconstruct to False, so that your custom SConstruct does not get overwritten by lbuild build. See the instructions inside our generated default SConstruct file.

SCons Methods

This module generates these SCons methods depending on the target.


Defaults to scons build size.

You can add these arguments to any of the SCons commands:

  • verbose=1: gives a more verbose output, so you can, for example, check what options the compiler is called with.
  • profile=release: Compile project with the release profile options (default).
  • profile=debug: Compile project with the debug profile options.

For a description of the release and debug profiles, see the modm:build module documentation.

Debug Profile

When working with the debug profile, make sure to add profile=debug to all commands, especially scons program profile=debug and scons debug profile=debug!

Some SCons commands take a firmware={GNU Build ID or path/to/firmware.elf} argument that specifies which firmware to use for the command. It is useful in combination with the scons artifact command to preserve a specific firmware version for later.

scons build

scons build profile={debug|release}

Compiles your application into an executable.

Example for a STM32 target:

 $ scons build
Compiling C++·· {debug|release}/main.o
Compiling C···· {debug|release}/modm/ext/gcc/cabi.o
Compiling C++·· {debug|release}/modm/src/modm/utils/dummy.o
Archiving······ {debug|release}/modm/libmodm.a
Indexing······· {debug|release}/modm/libmodm.a
Linking········ /build/{debug|release}/blink.elf

scons -c

scons -c profile={debug|release}

Cleans the build artifacts.

 $ scons -c
Removed {debug|release}/main.o
Removed {debug|release}/modm/ext/tlsf/tlsf.o
Removed {debug|release}/modm/src/modm/ui/display/virtual_graphic_display.o
Removed {debug|release}/modm/src/modm/utils/dummy.o
Removed {debug|release}/modm/libmodm.a
Removed {debug|release}/blink.elf
Removed {debug|release}/blink.lss

scons size

scons size profile={debug|release} [firmware={hash or file}]

Displays the static Flash and RAM consumption of your target.

Example for a STM32 target with 16MB external heap:

 $ scons size
Memory usage··· /build/{debug|release}/blink.elf
Program:  12.8 KiB (0.6% used)
(.data + .fastcode + .fastdata + .hardware_init + .reset + .rodata +
 .table.copy.extern + .table.copy.intern + .table.section_heap + + .text)

Data:      5.8 KiB (1.5% used) = 2936 B static (0.7%) + 3040 B stack (0.8%)
(.bss + .data + .fastdata + .stack)

Heap:     16.4 MiB
(.heap0 + .heap1 + .heap2 + .heap3 + .heap5 + .heap_extern)

scons program

scons program profile={debug|release} [port={serial-port}] [firmware={hash or file}]

Writes the executable onto your target via Avrdude or OpenOCD. This is a convenience wrapper around the programming options and methods defined in the modm:build module. (* only AVR and ARM Cortex-M targets)

Example for a STM32 target:

 $ scons program
╭────────────── /build/{debug|release}/blink.elf
╰───OpenOCD───> stm32f469nih
Open On-Chip Debugger 0.10.0
Info : using stlink api v2
Info : Target voltage: 3.259396
Info : stm32f4x.cpu: hardware has 6 breakpoints, 4 watchpoints
** Programming Started **
auto erase enabled
Info : device id = 0x10006434
Info : flash size = 2048kbytes
Info : Dual Bank 2048 kiB STM32F42x/43x/469/479 found
wrote 16384 bytes from file {debug|release}/blink.elf in 0.589736s (27.131 KiB/s)
** Programming Finished **
** Verify Started **
verified 13064 bytes in 0.296308s (43.056 KiB/s)
** Verified OK **
shutdown command invoked

scons program-fuses

scons program-fuses profile={debug|release} [firmware={hash or file}]

Writes all fuses onto your target connected to avrdude. See the modm:platform:core module for how to define the fuse values. (* only AVR targets)

scons program-dfu

scons program-dfu profile={debug|release} [firmware={hash or file}] [delay={seconds}]

Writes the executable onto your target via Device Firmware Update (DFU) over USB. A DFU bootloader is available on many STM32 microcontrollers and can be accessed by pressing the BOOT0-Button during startup.

Some DFU devices require additional delay to re-enumerate, which you can specify with the delay parameter (default is 5 seconds). (* only ARM Cortex-M targets)

$ scons program-dfu
Binary File···· /build/{debug|release}/blink.bin
╭────────────── /build/{debug|release}/blink.bin
╰─────DFU─────> stm32f469nih
dfu_stm32_programmer: program /build/{debug|release}/blink.bin
dfu-util 0.9
Opening DFU capable USB device...
ID 0483:df11
Run-time device DFU version 011a
Claiming USB DFU Interface...
Determining device status: state = dfuIDLE, status = 0
dfuIDLE, continuing
DFU mode device DFU version 011a
Device returned transfer size 2048
DfuSe interface name: "Internal Flash  "
Memory segment at 0x08000000   4 x 16384 = 65536 (rew)
Memory segment at 0x08010000   1 x 65536 = 65536 (rew)
Memory segment at 0x08020000   1 x 131072 = 131072 (rew)
Downloading to address = 0x08000000, size = 2060
Download        [                         ]   0%            0 bytes   Poll timeout 100 ms
   Poll timeout 0 ms
 Download from image offset 00000000 to memory 08000000-080007ff, size 2048
   Poll timeout 104 ms
   Poll timeout 0 ms
 Download from image offset 00000800 to memory 08000800-0800080b, size 12
   Poll timeout 104 ms
   Poll timeout 0 ms
File downloaded successfully
   Poll timeout 104 ms
   Poll timeout 0 ms
Transitioning to dfuMANIFEST state
scons: done building targets.

scons program-bmp

scons program-bmp profile={debug|release} [port={serial-port}] [firmware={hash or file}]

Black Magic Probe is convenient tool to convert cheap USB ST-LINK V2 clones to a fully functional GDB compatible debug adaptor for ARM Cortex microcontrollers. GDB can directly communicate with the debug adaptor making debugging easy and accessible. (* only ARM Cortex-M targets)

Black Magic Probe creates two serial devices, the first being the GDB interface and the second a plain serial adaptor for debugging purposes.

$ ls -l /dev/tty.usb*
crw-rw-rw-  1 root  wheel   21, 104 Feb 19 09:46 /dev/tty.usbmodemDEADBEEF
crw-rw-rw-  1 root  wheel   21, 106 Feb 19 09:46 /dev/tty.usbmodemDEADBEF1

You can let the tool guess the port or explicitly specify it:

$ scons program-bmp port=/dev/tty.usbmodemDEADBEEF
╭─Black─Magic── /build/{debug|release}/blink.elf
╰────Probe────> stm32f103rbt6
Remote debugging using /dev/tty.usbmodemDEADBEEF
Target voltage: unknown
Available Targets:
No. Att Driver
 1      STM32F1 medium density
Attaching to Remote target
warning: No executable has been specified and target does not support
determining executable automatically.  Try using the "file" command.
0x0800038e in ?? ()
Loading section .vector_rom, size 0xec lma 0x8000000
Loading section .table.section_heap, size 0xc lma 0x80013f8
Start address 0x8000e6c, load size 5120
Transfer rate: 10 KB/sec, 365 bytes/write.
Detaching from program: , Remote target
[Inferior 1 (Remote target) detached]
scons: done building targets.

scons program-remote

scons program-remote profile={debug|release} [host={ip or hostname}] [firmware={hash or file}]

Writes the executable onto your target connected to a remote OpenOCD process running on your own computer (host=localhost) or somewhere else. (* only ARM Cortex-M targets)

scons openocd

scons openocd

Starts an OpenOCD process to attach a remote debugger to (e.g. with scons program-remote or scons debug-remote). (* only ARM Cortex-M targets)

scons run

Compiles and executes your program on your computer. (* only Hosted targets)

scons debug

scons debug profile={debug|release} ui={tui|web} [firmware={hash or file}]

Launches OpenOCD in the background, then launches GDB in foreground with the correct executable with text-based or web-based GDBGUI UI. When GDB exits, it stops the OpenOCD process. (* only ARM Cortex-M targets)

This is just a convenience wrapper for the debug functionality defined in the modm:build module. To use GDBGUI you must have it installed via pip install gdbgui.

Choose the correct profile

When debugging, make sure to select the correct compilation profile. The firmware and the executable given to GDB have to be the same or you'll see GDB translate the program counter to the wrong code locations. When you suspect a bug in your firmware, consider that it was most likely compiled with the release profile, since that's the default. First try to scons debug profile=release, and if that doesn't help, compile and scons program profile=debug and try scons debug profile=debug again.

scons debug-bmp

scons debug-bmp profile={debug|release} ui={tui|web} port={serial-port} [firmware={hash or file}]

Launches GDB to debug via Black Magic Probe. (* only ARM Cortex-M targets)

scons debug-coredump

scons debug-coredump profile={debug|release} ui={tui|web} \
                     coredump={path/to/coredump.txt} \
                     [firmware={GNU Build ID or path/to/firmware.elf}]

Launches GDB for post-mortem debugging with the firmware identified by the (optional) firmware={hash or filepath} argument using the data from the coredump={filepath} argument. (* only ARM Cortex-M targets)

See the modm:platform:fault module for details how to receive the coredump data.

scons debug-remote

scons debug-remote profile={debug|release} ui={tui|web} [host={ip or hostname}] [firmware={hash or file}]

Debugs the executable via a remote OpenOCD process running on your own computer (localhost is default) or somewhere else. (* only ARM Cortex-M targets)

scons reset

scons reset

Resets the executable via OpenOCD. (* only ARM Cortex-M targets)

scons reset-bmp

scons reset-bmp [port={serial}]

Resets the executable via Black Magic Probe. (* only ARM Cortex-M targets)

scons reset-remote

scons reset-remote [host={ip or hostname}]

Resets the executable via a remote OpenOCD process running on your own computer (localhost is default) or somewhere else. (* only ARM Cortex-M targets)

scons log-itm

scons log-itm fcpu={HCLK in Hz}

Configures OpenOCD in tracing mode to output ITM channel 0 on SWO pin and displays the serial output stream. (* only ARM Cortex-M targets)

 $ scons log-itm fcpu=64000000
╭───OpenOCD───> Single Wire Viewer
╰─────SWO────── stm32f103rbt6
Open On-Chip Debugger 0.10.0
Licensed under GNU GPL v2
Info : The selected transport took over low-level target control.
loop: 57
loop: 58
loop: 59
loop: 60
loop: 61

See the modm:platform:itm module for details how to use the ITM as a logging output.

scons log-rtt

scons log-rtt [channel={int}]

Configures OpenOCD in RTT mode to output the chosen channel (default 0) via a simple telnet client. Disconnect with Ctrl+D. (* only ARM Cortex-M targets)

 $ scons log-rtt
╭───OpenOCD───> Real Time Transfer
╰─────RTT────── stm32f103rbt6
Info : rtt: Searching for control block 'modm.rtt.modm'
Info : rtt: Control block found at 0x20000008
loop: 57
loop: 58
loop: 59
loop: 60
loop: 61

See the modm:platform:rtt module for details how to use RTT for data transfer.

scons library

scons library profile={debug|release}

Generates only the static library libmodm.a without linking it to the application.

 $ scons library
Compiling C++·· {debug|release}/modm/ext/gcc/assert.o
Compiling C++·· {debug|release}/modm/src/modm/utils/dummy.o
Archiving······ {debug|release}/modm/libmodm.a
Indexing······· {debug|release}/modm/libmodm.a

scons symbols

scons symbols profile={debug|release} [firmware={hash or file}]

Dumps the symbol table for your executable.

 $ scons symbols [firmware={hash or file}]
Show symbols for '{debug|release}/blink.elf':
536871656 00000001 b (anonymous namespace)::nextOperation
536871657 00000001 b (anonymous namespace)::checkNextOperation
536871658 00000001 b (anonymous namespace)::error
536871444 00000001 b read_touch()::initialized
134228236 00000668 T I2C1_EV_IRQHandler
134224924 00001136 T otm8009a_init(unsigned char)
134221192 00001378 t _GLOBAL__sub_I_p
536871782 00002054 b (anonymous namespace)::txBuffer

scons listing

scons listing profile={debug|release} [firmware={hash or file}]

Decompiles your executable into an annotated assembly listing. This is very useful for checking and learning how the compiler translates C++ into assembly instructions:

 $ scons listing
Listing········ {debug|release}/blink.lss
 $ less {debug|release}/blink.lss
Disassembly of section .text:
08000d74 <main>:

 8000d74:   b508        push    {r3, lr}
 8000d76:   f7ff fcc9   bl  800070c <_ZN5Board10initializeEv>
 8000d7a:   f000 fd91   bl  80018a0 <_ZN5Board17initializeDisplayEv>
 8000d7e:   f7ff fc55   bl  800062c <_ZN5Board21initializeTouchscreenEv>
 8000d82:   f7ff feff   bl  8000b84 <_Z12blinkv>

scons bin

scons bin profile={debug|release} [firmware={hash or file}]

Creates a binary file of your executable.

 $ scons bin
Binary File···· {debug|release}/blink.bin

scons hex

scons hex profile={debug|release} [firmware={hash or file}]

Creates a Intel-hex file of your executable.

 $ scons hex
Hex File······· {debug|release}/blink.hex

scons uf2

scons uf2 profile={debug|release} [firmware={hash or file}]

Creates a UF2 compatible file of your executable. UF2 is a bootloader by Microsoft.

 $ scons uf2
UF2 File······· {debug|release}/blink.uf2

(* only ARM Cortex-M targets)

scons artifact

scons artifact profile={debug|release}

Caches the ELF and binary file of the newest compiled executable identified by the hash of the binary file in artifacts/{hash}.elf. You can change this path with the modm:build:scons:path.artifact option.

 $ scons artifact
╭───Artifact─── /build/release/blink.elf
╰────Cache────> artifacts/0214523ab713bc7bdfb37d902e65dae8305f4754.elf

scons qtcreator

Generates several files so that the project can be imported into Qt Creator via the .creator file importer. Note, that no compiliation or debugging features are supported, this is only meant for using the IDE as an editor.

Consider this an unstable feature

XPCC Generator Tool

The modm:communication:xpcc:generator module contains the Python tools to translate the XPCC XML declarations into various language implementations. This module contains a SCons wrapper tool, that understands the XML dependencies and automatically updates the generated files when it becomes necessary.

The wrapper tool is automatically used when the generator module is detected, and its options are evaluated for the wrapper as follows:


The generated files are available as a top-level #include <identifiers.hpp>.

Information Tool

Our info SCons tool generates a set of header files containing information about the repository state.

A call to env.InfoGit(with_status={True, False}) will generate a <info_git.h> header file and add these two defines to the command line CPP options:

  • MODM_GIT_STATUS: defined only if called with with_state=True.

You can enable this by setting the modm:build:info.git option.

Increased build time

Since the git repository status can change at any time, it needs to be checked on every build. This adds less than a second to every build.

A call to env.InfoBuild() will generate a <info_build.h> header file and add this define to the command line CPP options:


You can enable this by setting the option.

Respect developers privacy

This information is placed into the firmware in cleartext, so it will be trivial to extract from a memory dump. Consider this information public as soon as it is uploaded to your target. Make sure you only use the information you absolutely need!

Bitmap Tool

If the modm:build:image.source is defined as a path, it'll be searched for .pbm files to convert into C++ data files using the bitmap tool:

source, header = env.Bitmap(bpm_file)

See the GraphicsDisplay::drawImage() method in the modm:ui:display module for how to use these generated files. The directory is added to the include search paths, so the generated files can be accessed as #include <image.hpp>.



Path to SConstruct CacheDir

If value is $cache, the cache is placed into the top-level build/ folder. You can disable CacheDir by setting an empty string.

Default: []
Inputs: [Path]


Generate a SConstruct file

This overwrites any top-level SConstruct file!

Default: yes
Inputs: [yes, no]


Path to Artifact Store

The artifact folder contains ELF files named by their GNU build id hash. This allows identification of firmware on the device via serial output and is useful for archiving or post-mortem debugging.

Default: artifacts
Inputs: [Path]



Formatting compile flags for SCons

Inputs: [Callable]

SCons tool paths to be added to the Environment

Inputs: [Path]


SCons tools to be added to the Environment

Inputs: [String]