Very small, safe, lightning fast, yet portable preemptive RTOS with SMP support.
picoRTOS is a small hard RTOS with as little overhead as humanly possible.
- Book of requirements
- How to use
- API Documentation
- Supported architectures
- Featured devices
- Working principle
- Inter-processus communication
- Shared priorities
- Interrupt management
- Staging tree
- Featured demos
OpenPicoRTOS has been designed with these requirements in mind:
- Compliance with "The Power Of 10" from the NASA/JPL (https://en.wikipedia.org/wiki/The_Power_of_10:_Rules_for_Developing_Safety-Critical_Code)
- Compliance with MISRA C 2012
- Limited use of inline assembly:
- Inline assembly should be side-effect free (no use or modification of variables)
- Inline assembly can be safely removed from the static analysis
- Smallest footprint possible
- Fully static
- Fully predictable
- High portability
- Lowest overhead possible
- Support for SMP
- Less than 400 lines of code
More information here: https://github.com/jnaulet/OpenPicoRTOS/blob/main/etc/Requirements.md
To create a project compatible with OpenPicoRTOS you first need to add a specific kind of Makefile to your project.
You can find a very basic template here: https://github.com/jnaulet/OpenPicoRTOS/blob/v1.9.x/etc/Makefile.template
Simply type:
# make menuconfig
And configure your project according to your needs. You can find a lot of examples in the demo directory.
# make
# make staticcheck
or, alternatively:
# make splint
# make cppcheck
Using the template makefile automatically offers you access to a new set of targets for the OpenPicoRTOS build system, directly in your project directory:
Cleaning targets:
clean - Remove most generated files but keep the config and
enough build support to build external modules
mrproper - Remove all generated files + config + various backup files
distclean - mrproper + remove editor backup and patch files
Configuration targets:
config - Update current config utilising a line-oriented program
nconfig - Update current config utilising a ncurses menu based program
menuconfig - Update current config utilising a menu based program
xconfig - Update current config utilising a QT based front-end
gconfig - Update current config utilising a GTK based front-end
oldconfig - Update current config utilising a provided .config as base
localmodconfig - Update current config disabling modules not loaded
localyesconfig - Update current config converting local mods to core
silentoldconfig - Same as oldconfig, but quietly, additionally update deps
defconfig - New config with default from ARCH supplied defconfig
savedefconfig - Save current config as ./defconfig (minimal config)
allnoconfig - New config where all options are answered with no
allyesconfig - New config where all options are accepted with yes
allmodconfig - New config selecting modules when possible
alldefconfig - New config with all symbols set to default
randconfig - New config with random answer to all options
listnewconfig - List new options
oldnoconfig - Same as silentoldconfig but set new symbols to n (unset)
Other generic targets:
all - Build target
Test targets:
check - Run static analysis on all basic platforms + unit tests
Static analysis targets:
splint - Run splint -checks on the source code
cppcheck - Run cppcheck --enable=all on the source code
staticcheck - Run both previous checks
make V=0|1 [targets] 0 => quiet build (default), 1 => verbose build
HTML documentation of the complete API is available in the documentation directory and at the following address: https://jnaulet.github.io/OpenPicoRTOS
- ARM Cortex-M0+
- ARM Cortex-M3
- ARM Cortex-M4/F
- ARM Cortex-M7
- Atmel ATMega Series
- Atmel TinyAVR Series
- Intel 8051 / MCS51
- MIPS M51xx / PIC32Mx
- RISC-V RV32IMAC
- RISC-V RV32EC
- PowerPC e200z4
- PowerPC e200z7
- TI C2000 / c28x
- PowerPC e200z4 SMP
- PowerPC e200z7 SMP
- RP2040 SMP
- POSIX threads / Linux
- WIN32 threads / Windows
- Atmel ATMega2560
- Atmel ATMega328P
- Atmel ATMega32u4
- Atmel ATSAM3X8E
- Atmel ATSAMD5x/E5x
- Atmel ATtiny817
- Atmel ATtiny88
- Atmel ATtiny1607
- Cypress CY7C6801xA / EZ-USB FX2
- GigaDevice GD32VF103
- LogicGreen LGT8F328P
- Microchip PIC32MZ-EF
- Nuvoton N76E003
- NXP MPC574x series
- NXP MPC577x series
- Raspberry Pico RP2040
- Renesas RA4M1
- STC MCU STC12C5Axx series
- STMicroelectronics STM32F10xxx series
- STMicroelectronics STM32F401x series
- STMicroelectronics STM32H743/750
- Texas Instruments TMS320F2837xD
- WCH CH32V003
On every new cycle (tick), picoRTOS stops the execution of the current task and runs the highest
priority task available.
A few criterias make a task available for scheduling, it has to be:
- Ready (aka not sleeping/busy)
- The tick modulo has to match the task sub-priority (see shared priorities)
- In case of SMP, the task core mask has to match the current running core
Any syscall (picoRTOS_schedule, picoRTOS_sleep or picoRTOS_sleep_until) will allow picoRTOS to run the next highest priority task available until it reaches idle or a new tick occurs and the cycle starts over.
Task execution order goes from highest (0) to lowest (CONFIG_TASK_COUNT - 1) priority.
Example:
tick: prio0 -> prio1 -> prio2 -> ... (towards idle)
tick: prio0 -> prio1 -> prio2 -> ... (towards idle)
...
No memory management is offered, everything is static, which makes the static analyzer's job much easier for critical applications.
The following IPCs are provided:
- futexes (require arch_test_and_set)
- re-entrant mutexes (require arch_compare_and_swap)
- conditions (require mutexes)
- queues (requires futexes)
Version 1.7 introduces shared priorities for tasks, a.k.a round-robin scheduling.
When several tasks share the same priority, the order of execution (highest to lowest priority) doesn't change, but these tasks will be executed alternatively, on a tick modulo basis.
Example with 2 tasks (B & C) sharing a priority of 1:
tick 0: taskA (prio 0) -> taskB (prio 1) -> taskD (prio 2) -> ...
tick 1: taskA (prio 0) -> taskC (prio 1) -> taskD (prio 2) -> ...
tick 2: taskA (prio 0) -> taskB (prio 1) -> taskD (prio 2) -> ...
tick 3: taskA (prio 0) -> taskC (prio 1) -> taskD (prio 2) -> ...
...
Version 1.5 introduces contextual interrupt management as an experimental feature.
All architectures are supported (at least partially) at the moment.
This feature should be used with care, as interrupts tend to destroy the real-time part in "RTOS".
Version 1.8 introduces the staging tree.
This tree contains code that builds & fits the book of requirements but could not be tested for one reason or the other.
This code should be considered highly experimental until validation.
Basic demo code is provided for the following boards:
- Adafruit ItsyBitsy M4 Express
- Arduino Due
- Arduino Mega2560
- Arduino Nano v3 + LGT8Fx clone (staging)
- Arduino Uno
- Arduino Uno R4 Minima
- ATtiny817-Xplained Mini
- ATtiny1607 Curiosity Nano
- Curiosity 2.0 PIC32 MZ EF
- DevEBox STC-C51
- DevEBox STM32H7xx_M
- Infineon EZ-USB FX2LP
- MH-Tiny / MH-Tiny88 (staging)
- Nuvoton N76E003 / MCU-E003
- NXP Devkit MPC5748G (dual-core SMP)
- NXP MPC5775E-EVB (dual-core SMP) (staging)
- Sipeed Longan Nano
- STMicro STM32F103C8T6 development board (staging)
- STMicro STM32F401RCT6 development board (staging)
- Texas Instruments Launchxl-f28379d
- Raspberry Pi Pico (single core & SMP)
- WCH CH32V003F4P6 eval board (staging)
A portability demo is available in demo/amigaball-lcd and works with the follwing boards (+0.96" LCD):
- Adafruit ItsyBitsy M4 Express
- Sipeed Longan Nano
- Texas Instruments Launchxl-f28379d
- Raspberry Pi Pico SMP
- DevEBox STM32H7xx_M / STM32H743VIT6