Description

An operating system runs on Cortex-M micro controllers.

Plan:

1, run fully on emulator first ... Done
1, logging system, through rdimon ... Done
1, reset handler and vector table ... Done
1, implement USART I/O output, for debugging purpose ... Done
1, implement systick timer ... Done
1, implement atomic operations ... Done
1, data types
1, sleep
1, multi tasking
1, implement minimal memory management
1, inter process communication
1, implement a minimal C standard library function.

hardware

MCU: STM32F405RET6
schematic: https://www.olimex.com/Products/ARM/ST/STM32-H405/resources/STM32-H405_sch.pdf

emulate

# example, done, successful
# redirect USART1 output to terminal
# compile with --specs=rdimon.specs
qemu-system-arm \
    -M olimex-stm32-h405 \
    -cpu cortex-m4 \
    -nographic \
    -serial stdio \
    -monitor null \
    -semihosting \
    --semihosting-config enable=on,target=native \
    -kernel build/main.elf

references

1, PM0214 Programming manual STM32 Cortex®-M4 MCUs and MPUs programming manual
1, RM0090 Reference manual STM32F405/415, STM32F407/417, STM32F427/437 and STM32F429/439 advanced ARM®-based 32-bit MCUs
1, STM32F405xx STM32F407xx Arm® Cortex®-M4 32b MCU+FPU, 210DMIPS, up to 1MB Flash/192+4KB RAM, USB OTG HS/FS, Ethernet, 17 TIMs, 3 ADCs, 15 comm. interfaces & camera
1, Cortex-M4 Revision r0p0 Technical Reference Manual
1, Arm v7-M Architecture ® Reference Manual
1, IEEE & The Open Group - IEEE Std 1003.1-2017
1, Procedure Call Standard for the ARM® Architecture
1, https://github.com/ARM-software/abi-aa/releases

questions and thoughts

How to test spin lock with single thread and systick timer?

For example, lock lock1 at 200 sys ticks.
unlock lock1 at 400 sys ticks.

try lock lock1 again at 300 sys tick.

why there are space between last named argument and va_list?

Typedef:va_list
Base type:struct __va_list { void *__ap; }
Notes:A va_list may address any object in a parameter list. Consequently, the first object addressed may only have word alignment (all objects are at least word aligned), but any double- word aligned object will appear at the correct double-word alignment in memory. In C++, __va_list is in namespace std.