Allow FetchContent usage in external projects (#1166)

Author: nicovanduijn

CMakeLists.txt

@@ -1,5 +1,5 @@
 
-cmake_minimum_required(VERSION 3.15)
+cmake_minimum_required(VERSION 3.21)
 cmake_policy(SET CMP0048 NEW) # project version
 cmake_policy(SET CMP0076 NEW) # full paths
 
@@ -174,4 +174,6 @@ add_subdirectory(source)
 add_subdirectory(tools)
 add_subdirectory(test)
 
-FetchContent_MakeAvailable(freertos_kernel cmock)
+if(PROJECT_IS_TOP_LEVEL)
+    FetchContent_MakeAvailable(freertos_kernel cmock)
+endif()

README.md

@@ -60,13 +60,12 @@ FetchContent_Declare( freertos_plus_tcp
   - this particular example supports a native and cross-compiled build option.
 
 ```cmake
-set( FREERTOS_PLUS_FAT_DEV_SUPPORT OFF CACHE BOOL "" FORCE)
 # Select the native compile PORT
-set( FREERTOS_PLUS_FAT_PORT "POSIX" CACHE STRING "" FORCE)
-# Select the cross-compile PORT
+set( FREERTOS_PLUS_TCP_NETWORK_IF "POSIX" CACHE STRING "" FORCE)
+# Or: select a cross-compile PORT
 if (CMAKE_CROSSCOMPILING)
-  # Eg. Zynq 2019_3 version of port
-  set(FREERTOS_PLUS_FAT_PORT "ZYNQ_2019_3" CACHE STRING "" FORCE)
+  # Eg. STM32Hxx version of port
+  set(FREERTOS_PLUS_TCP_NETWORK_IF "STM32HXX" CACHE STRING "" FORCE)
 endif()
 
 FetchContent_MakeAvailable(freertos_plus_tcp)