FreeRTOS: allow override startup hooks default implementation

The default behaviour is do nothing: scheduler has to be started manually by the user.
Use AUTOSTART_FREERTOS if you declare tasks in your setup() and use them in loop().
Use EARLY_AUTOSTART_FREERTOS if you need the scheduler to be already running in setup().

Libraries that need to use threads/semaphores during setup() (for example, to implement the usual

myObj.begin(); <- this starts a thread
while (!myObj) {  <- this becomes true when the thread is unlocked
  delay();
}

will need to declare EARLY_START_FREERTOS_HOOK in one of their cpp files

Author: facchinm

cores/arduino/main.cpp

@@ -64,6 +64,8 @@ void unsecure_registers() {
 #define str(s) #s
 
 extern "C" void Stacktrace_Handler(void);
+extern "C" __attribute__((weak)) void start_freertos_on_header_inclusion() {}
+extern "C" __attribute__((weak)) void early_start_freertos_on_header_inclusion() {}
 
 void arduino_main(void)
 {
@@ -111,7 +113,9 @@ void arduino_main(void)
    Serial.begin(115200);
 #endif
    startAgt();
+   early_start_freertos_on_header_inclusion();
    setup();
+   start_freertos_on_header_inclusion();
    while (1)
    {
       loop();

libraries/Arduino_FreeRTOS/src/Arduino_FreeRTOS.h

@@ -27,6 +27,27 @@ extern "C" {
 #include "lib/FreeRTOS-Kernel-v10.5.1/semphr.h"
 #include "lib/FreeRTOS-Kernel-v10.5.1/task.h"
 #include "lib/FreeRTOS-Kernel-v10.5.1/timers.h"
+#include <stdbool.h>
+
+
+// If you need to automatically start FREERTOS, declare either EARLY_AUTOSTART_FREERTOS or
+// AUTOSTART_FREERTOS in your library or sketch code (.ino or .cpp file)
+//
+// EARLY_AUTOSTART_FREERTOS -> if you need the scheduler to be already running in setup()
+// AUTOSTART_FREERTOS -> if you only declare the threads in setup() and use them in loop()
+
+void _start_freertos_on_header_inclusion_impl(bool early_start);
+void early_start_freertos_on_header_inclusion();
+void start_freertos_on_header_inclusion();
+#define EARLY_AUTOSTART_FREERTOS \
+    void early_start_freertos_on_header_inclusion() { \
+        _start_freertos_on_header_inclusion_impl(true); \
+    }
+#define AUTOSTART_FREERTOS \
+    void start_freertos_on_header_inclusion() { \
+        _start_freertos_on_header_inclusion_impl(false); \
+    }
+
 
 #ifdef __cplusplus
 }

libraries/Arduino_FreeRTOS/src/portable/FSP/port.c

@@ -32,6 +32,7 @@
 #include "FreeRTOSConfig.h"
 #include "../../lib/FreeRTOS-Kernel-v10.5.1/FreeRTOS.h"
 #include "../../lib/FreeRTOS-Kernel-v10.5.1/task.h"
+#include "portmacro.h"
 
 #if BSP_TZ_NONSECURE_BUILD
  #include "tz_context.h"
@@ -225,6 +226,33 @@ static void prvTaskExitError(void);
 
 #endif
 
+
+static void sketch_thread_func(void* arg) {
+    bool early_start = (bool)arg;
+    if (early_start) {
+        setup();
+    }
+    while (1)
+    {
+        loop();
+    }
+}
+
+void _start_freertos_on_header_inclusion_impl(bool early_start) {
+    static TaskHandle_t sketch_task;
+    if (xTaskGetSchedulerState() != taskSCHEDULER_RUNNING) {
+        xTaskCreate(
+        (TaskFunction_t)sketch_thread_func,
+        "Sketch Thread",
+        4096 / 4,   /* usStackDepth in words */
+        (void*)early_start,   /* pvParameters */
+        4,         /* uxPriority */
+        &sketch_task /* pxCreatedTask */
+        );
+        vTaskStartScheduler();
+    }
+}
+
 /* Arduino specific overrides */
 void delay(uint32_t ms) {
     if (xTaskGetSchedulerState() == taskSCHEDULER_RUNNING) {