Add FreeRTOS library

[maxgerhardt]

The core should have a builtin FreeRTOS library, akin to STM32FreeRTOS.

This additionally requires that the core allows hooking of the SysTick function and possibly other functions.

[flute2k3]

Looking forward to testing it!

[maxgerhardt]

FreeRTOS is now a core built-in library that can be used as https://github.com/CommunityGD32Cores/ArduinoCore-GD32/tree/main/libraries/FreeRTOS/examples/FreeRTOS_Blink shows. There's a default config file, but if GD32FreeRTOSConfig.h exists in the src or include folder (for PlatformIO), it will be used instead. Successfully tested on a GD32F303CC.

[flute2k3]

today I got chance to test the freeRTOS, I modified the codes based on the example, successfully blink 2 LEDs, impressive, thanks!

I wonder if this buildin freeRTOS does not support dynamically allocated memory? when I try to use xTaskCreate(), I got below error:
xTaskCreate' was not declared in this scope

[maxgerhardt]

In the default FreeRTOS config, dynamic allocation is disabled in favor of static allocation. This prevents runtime out-of-memory situations for low-RAM microcontrollers. Irregardless, you can change the values

ArduinoCore-GD32/libraries/FreeRTOS/examples/FreeRTOS_Blink/GD32FreeRTOSConfig.h

Lines 51 to 52 in dfa7ccb

	#define configSUPPORT_DYNAMIC_ALLOCATION 0
	#define configSUPPORT_STATIC_ALLOCATION 1

per-project to 0 or 1. Setting the first to 1 will enable xTaskCreate.

[flute2k3]

Hum, I will make a note on it if needed, by the way, do we have a rough standards say for example how much RAM is defined as low-RAM mcu? what about 303CC, low or ok?