Simple example FreeRTOS for nRF52

README.md

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+# Simple Example of FreeRTOS porting on a Custom nRF52 Board
+
+By default, the nRF52 chip is not supported by FreeRTOS. However, since it uses an ARM Cortex-M4, we can manually port FreeRTOS to it.
+
+This repository provides basic examples of porting FreeRTOS to the nRF52 using PlatformIO with the Arduino framework. The FreeRTOS kernel files are located in `lib/FreeRTOS/`, so we need to add the following build flags and sources to `platformio.ini`:
+
+```ini
+build_flags =
+  -I lib/FreeRTOS/include
+  -I lib/FreeRTOS/portable/GCC/ARM_CM4F
+build_src_filter  =
+  +<*>
+  +<lib/FreeRTOS/*.c>
+  +<lib/FreeRTOS/portable/GCC/ARM_CM4F/*.c>
+  +<lib/FreeRTOS/portable/MemMang/*.c>
+```
+The FreeRTOS kernel used in this example is version 11.0.0.
+
+## Examples
+
+- ### Simple FreeRTOS for LED Blinking with Two LEDs
+  This example modifies `FreeRTOSConfig.h` to add the following handlers, which connect the MCU to FreeRTOS:
+  
+    - `#define vPortSVCHandler SVC_Handler`
+    - `#define xPortPendSVHandler PendSV_Handler`
+    - `#define xPortSysTickHandler SysTick_Handler`
+  
+  The SysTick timer uses the CPU's main clock.
+
+- ### Simple FreeRTOS with Low-Power Mode and LED Blinking
+  In this example, `FreeRTOSConfig.h` is modified to add:
+
+    - `#define vPortSVCHandler SVC_Handler`
+    - `#define xPortPendSVHandler PendSV_Handler`
+
+  The SysTick timer uses the RTC's clock, set with `#define configSYSTICK_CLOCK_HZ (32768UL)`. Additionally, the default SysTick behavior of the RTOS is overridden in `low_power_config.cpp`.
+
+    ![Power Measurement](Figures/LowPowerMode.png "Power measurement when LED is off")  
+    **Figure:** Power consumption measurement shows ~2.5 µA at 3V when the LED is off.
+
+
+**Note: In this example, I am using a custom board based on nRF52832. Also, for the programmer, CMSIS-DAP programmer hardware is used (with 4 connections: VCC, GND, DIO, CLK). Adjust its upload_protocol and debug_tool according to your needs.*