stmos is an attempt to implement a general-purpose operating system on ARM microcontrollers. The name "stmos" is due to the fact that this was first implemented on an STM32L476RG MCU (ARM Cortex-M4F), and the operating system still includes many operations/values that are specific to this processor (currently limiting the portability of this OS).
Eventually, this OS aims to support at least all Cortex-M MCUs.
Features:
- Advanced heap that does its best to keep large chunks of memory available
- Round-robin multitasking that keeps tasks in userspace
- A virtual filesystem implementation with stdio/initrd built into the kernel
- Ability to execute ELF files loaded from the filesystem
- A nearly complete C standard library implementation available to loaded ELFs (using PDCLib)
- libgpio: The first userspace library; makes GPIO available to loaded ELFs
Currently supported processors:
- STM32L476RG (board: NUCLEO-L476RG)
To build stmos, you'll need the following programs:
- The arm-stmos toolchain (see the
arm-stmosfolder) - openocd
- gdb (with multiarch support,
gdb-multiarchon Debian)
To compile stmos simply run make (-j supported). To upload, use run.sh to
launch OpenOCD and GDB; then, do lo to load stmos, and c to begin execution.
Currently, the only available filesystem driver is for the initrd. Files in the
folder src/initrd/files are put into the initrd. C source files in
src/initrd are compiled (with libgpio available), placing the programs in
src/initrd/files
What's next for stmos?
- Processor independence
- SD card support?
- Display support? (ILI....)
- Support for running a popular program (e.g. a shell like sash, maybe lua)
- Growth of features available to loaded ELFs (better execve, signals?, etc.)