Unexpected behavior when using freeRTOS with two tasks

Question

I am using MPU9250-breakout board with Arduino Uno.
The library I used is from here.
Below is my code.

#include <Arduino_FreeRTOS.h>

#include "mpu9250.h"

MPU9250 IMU(Wire,0x68);
int status;

void task_1(void *pvParameters)
{
  (void) pvParameters;

  for (;;)
  {
  }
}

void task_2(void *pvParameters)
{
  (void) pvParameters;

  for (;;)
  {
  }
}

void setup() {
  Serial.begin(115200);
  while(!Serial) {}

  status = IMU.begin();
  if (status < 0) {
    Serial.println("IMU initialization unsuccessful");
    Serial.println("Check IMU wiring or try cycling power");
    Serial.print("Status: ");
    Serial.println(status);
    while(1) {}
  }

  xTaskCreate(
  task_2,
  (const portCHAR *)"task2", // A name just for humans
  128, // Stack size
  NULL,
  1, // priority
  NULL);

  xTaskCreate(
  task_1,
  (const portCHAR *)"task1", // A name just for humans
  128, // Stack size
  NULL,
  1, // priority
  NULL);

}

void loop()
{

}

The problem is that when there are two tasks defined, the program will be restarted automatically. But when I comment out task_1, the program works fine. The result value of xTaskCreate is correct.

I guess the problem might be the stack or heap size is too small, but I've increased stack and heap size and it's still doesn't work.

Can anyone tell me where the problem might be from?

Do you use cooperative or preemptive scheduler? Not enough memory? Do you know that 128 for stack type is of size StackType_t which may be 4bytes, thus effectively allocating 512B of stack? I also don't see where is your scheduler started. — tilz0R
Neither, in arduino freeRTOS example, it didn't call such thing. Should I call that in my example? — Lion Lai

Unknown Unknown · Accepted Answer · 2018-08-16T15:25:12

At the end of your setup(), you need to start the scheduler:

// Now the task scheduler, which takes over control of scheduling individual tasks, //is automatically started.

vTaskStartScheduler();

That is all I see different between my project which works and yours.

Unexpected behavior when using freeRTOS with two tasks

3 Answers