This is the documentation for the latest (main) development branch of Zephyr. If you are looking for the documentation of previous releases, use the drop-down list at the bottom of the left panel and select the desired version.

Minimal footprint


This sample provides an empty main() and various configuration files that can be used to measure Zephyr’s minimal ROM footprint in different configurations.

The following configuration files are available:

  • mt.conf: Enable multithreading

  • no-mt.conf: Disable multithreading

  • no-preempt.conf: Disable preemption

  • no-timers.conf: Disable timers

  • arm.conf: Arm-specific disabling of features

Building and measuring ROM size

The following combinations are suggested for comparing ROM sizes in different configurations. They all target the reel board (Arm Aarch32 architecture).

  • Multithreading enabled

    • Reference ROM size: 7-8KB

    west build -b reel_board -d build/reel_board/mt samples/basic/minimal -- -DCONF_FILE="common.conf mt.conf arm.conf"
    west build -t rom_report -d build/reel_board/mt
  • Multithreading enabled, no preemption

    • Reference ROM size: 7-8KB

    west build -b reel_board -d build/reel_board/mt-no-preempt samples/basic/minimal -- -DCONF_FILE="common.conf mt.conf no-preempt.conf arm.conf"
    west build -t rom_report -d build/reel_board/mt-no-preempt
  • Multithreading enabled, no preemption, timers disabled

    • Reference ROM size: 3-4KB

    west build -b reel_board -d build/reel_board/mt-no-preempt-no-timers samples/basic/minimal -- -DCONF_FILE="common.conf mt.conf no-preempt.conf no-timers.conf arm.conf"
    west build -t rom_report -d build/reel_board/mt-no-preempt-no-timers
  • Multithreading disabled, timers enabled

    • Reference ROM size: 4-5KB

    west build -b reel_board -d build/reel_board/no-mt samples/basic/minimal -- -DCONF_FILE="common.conf no-mt.conf arm.conf"
    west build -t rom_report -d build/reel_board/no-mt
  • Multithreading disabled, timers disabled

    • Reference ROM size: 2-3KB

    west build -b reel_board -d build/reel_board/no-mt-no-timers samples/basic/minimal -- -DCONF_FILE="common.conf no-mt.conf no-timers.conf arm.conf"
    west build -t rom_report -d build/reel_board/no-mt-no-timers