Object Oriented tasks - variables going out of scope?

Kernel
1

I’m trying to use C++ objects as tasks and am having trouble getting member data passed into a new instance.

For example I have a button monitor that reports presses to a seat manager but none of the instance variables populate inside my task loop.

Edit: this is code for an ESP32 with their implementation of FreeRTOS.

Here’s the base class for a task object

class TaskBase {
  public:

    TaskBase(const char* name, UBaseType_t priority, configSTACK_DEPTH_TYPE stackDepth=configMINIMAL_STACK_SIZE) {
      xTaskCreate(&taskLoop, name, stackDepth, this, priority, &handle);
    }

  protected:
    virtual void task() = 0;

  private:
    TaskHandle_t handle;

    static void taskLoop(void* param) {
      TaskBase* obj = const_cast<TaskBase*>(static_cast<const TaskBase*>(param));
      obj->task();
    }
};

A button monitor derived from it

class ButtonMonitor : public TaskBase {
  public:
    ButtonMonitor( uint8_t pin,
                   QueueHandle_t queue,
                   touch_value_t capThreshold = 40000,
                   const char* name = "Button Monitor",
                   UBaseType_t priority = PRIO_MEDIUM,
                   configSTACK_DEPTH_TYPE stackDepth = 2000 );

  protected:
    void task();

  private:
    static const TickType_t xDebounceDuration      = pdMS_TO_TICKS(50);
    static const TickType_t xLongPressDuration     = pdMS_TO_TICKS(700);
    static const TickType_t xPressDuration         = pdMS_TO_TICKS(250);
    static const TickType_t xSequentialTapDuration = pdMS_TO_TICKS(250);
    static const TickType_t xWaitDuration          = pdMS_TO_TICKS(20);

    uint8_t _pin;
    touch_value_t _capThreshold;
    QueueHandle_t _sendQueue;

};

Button monitor implementation

ButtonMonitor::ButtonMonitor( uint8_t pin,
                              QueueHandle_t queue,
                              touch_value_t capThreshold,
                              const char* name,
                              UBaseType_t priority,
                              configSTACK_DEPTH_TYPE stackDepth ) :
  TaskBase( name, priority, stackDepth ), _pin(pin), _sendQueue(queue), _capThreshold(capThreshold) {

}

void ButtonMonitor::task() {
  log_i("pin %d", _pin);
  log_i("cap threshold %d", _capThreshold);
  while(1) {
    // FIXME use _pin and _capThreshold
    bCurrPressed = touchRead(10) > 40000;

    // a bunch of correctly working button code

    log_i("Queue %d Seat %2d Touches %d", _sendQueue, sensorData.seat, sensorData.reading);
    xQueueSend(_sendQueue, &sensorData, portMAX_DELAY);

    // more button code
    vTaskDelay(20);  // FIXME use xWaitDuration
  }
}

main (edited for clarity)

void setup() {
  SemaphoreHandle_t xBoardStateChangedSemaphore = xSemaphoreCreateBinary();
  QueueHandle_t xSeatManagerReceiveQueue = xQueueCreate(2, sizeof(SensorData_t));

  vTaskDelay(500);
  ButtonMonitor b( 10, xSeatManagerReceiveQueue, 40000 );
  log_i("Button monitor go");

  vTaskDelay(500);
  SeatManager s( xSeatManagerReceiveQueue, xBoardStateChangedSemaphore );
  log_i("Seat manager go");
}

Run log

[    95][I][esp32-hal-psram.c:96] psramInit(): PSRAM enabled
[  1100][I][main.cpp:16] setup(): Blarkey Blark & The Blunky Funch in the house!!!!
o  1600][I][mutton_monitor.cpp[: 1 71]6 0t0a]s[kI(])[:b uptitno n1_0m
t␀i
or.cpp:17] task(): pin 10
[  1600][I][button_monitor.cpp:18] task(): cap threshold 40000
[  2100][I][main.cpp:27] setup(): Seat manager go
[  3764][I][button_monitor.cpp:81] task(): Queue 0 Seat  0 Touches 2

assert failed: xQueueGenericSend queue.c:820 (pxQueue)


Backtrace: 0x40377332:0x3fcec880 0x4037aab5:0x3fcec8a0 0x403803d1:0x3fcec8c0 0x4037b2e3:0x3fcec9f0 0x420017cb:0x3fceca30 0x4201f649:0x3fceca80

  #0  0x40377332:0x3fcec880 in panic_abort at /Users/ficeto/Desktop/ESP32/ESP32S2/esp-idf-public/components/esp_system/panic.c:408
  #1  0x4037aab5:0x3fcec8a0 in esp_system_abort at /Users/ficeto/Desktop/ESP32/ESP32S2/esp-idf-public/components/esp_system/esp_system.c:137
  #2  0x403803d1:0x3fcec8c0 in __assert_func at /Users/ficeto/Desktop/ESP32/ESP32S2/esp-idf-public/components/newlib/assert.c:85
  #3  0x4037b2e3:0x3fcec9f0 in xQueueGenericSend at /Users/ficeto/Desktop/ESP32/ESP32S2/esp-idf-public/components/freertos/queue.c:821 (discriminator 2)
  #4  0x420017cb:0x3fceca30 in ButtonMonitor::task() at src/button_monitor.cpp:82
  #5  0x4201f649:0x3fceca80 in TaskBase::taskLoop(void*) at src/task_base.h:33

As you can see, the log shows the ButtonManager instance correctly assigns _pin and _capThreshold but when I reference them in the while loop I get zeros instead. The panic happens when writing data to the queue.

Seems I’m missing some variable scope concept here. Any suggestions? Thanks.

2

also, you can not use vTaskDelay() in main(), only in tasks.

3

Probably this might be the problem resp. the solution: Task-class cast in callback method not working - #9 by hs2

5

This might be the case. I’ll look deeper today. Thank you.

I forgot to mention that this is ESP32 code. setup() is already running in a task.

6

You are declaring object instances in the function setup, which will be destroyed when that function returns.

1 Like
7

This is the answer. Thank you.