I'm having trouble getting QTimer to work in a console (no GUI) application.

When I start the timer, it goes active, but never times out.

When I tried using the static QTimer::singleShot method, I get a runtime error:

QObject::startTimer: QTimer can only be used with threads started with QThread
I've tried explicitly using Qt::QueuedConnection for the connection to the slot that tries to start the timer, but that makes no difference (and I think that's the default anyway).

Maybe the signal that's connected to the slot that starts the timer is on a different thread than what instantiated the QObject. The signal is emitted from an interrupt handler registered by the wiringPiISR() function provided by the wiringPi package.

Here's the code:

powerControl.h
Qt Code: 
  1. #ifndef POWERCONTROL_H
  2. #define POWERCONTROL_H
  3. #define GPIO3 5
  4. #include <QObject>
  5. #include <QTimer>
  6. #include <QDebug>
  7.  
  8. class PowerControl : public QObject
  9. {
  10.  
  11.     Q_OBJECT
  12. public:
  13.     explicit PowerControl(QObject *parent = 0);
  14.  
  15.     static PowerControl *getInstance() {return instance;}
  16.  
  17.     static void handleEdgeBoth(void);
  18.  
  19.     virtual void handleIrq(bool afterEdgeState);
  20.     ~PowerControl();
  21.  
  22. private:
  23.      static PowerControl *instance;
  24.      QTimer debounceTimer;
  25.      QTimer tapTimer;
  26.      QTimer powerOffTimer;
  27.      static unsigned long lastTime;
  28.  
  29. signals:
  30.      void fallingEdge(void);
  31.      void risingEdge(void);
  32.      void buttonPushed(void);
  33.      void tapDetected(void);
  34.      void longPressDetected();
  35.  
  36. public slots:
  37. private slots:
  38.      void edgeDetected(bool);
  39.      void bounceFinished(void) {qDebug() << "Bounce timeout";}
  40.      void tapTimeout(void) {qDebug() << "tap timeout";}
  41.  
  42.  
  43. #define DEBOUNCE_TIME 10
  44. };
  45.  
  46. #endif // POWERCONTROL_H
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powerControl.cpp
Qt Code: 
  1. #include "powercontrol.h"
  2. #include "wiringPi.h"
  3. #include <QDebug>
  4.  
  5. PowerControl *PowerControl::instance;
  6. unsigned long PowerControl::lastTime = 0;
  7.  
  8. PowerControl::PowerControl(QObject *parent) : QObject(parent)
  9. {
  10.     debounceTimer.setSingleShot(true);
  11.     debounceTimer.setInterval(DEBOUNCE_TIME);
  12.     tapTimer.setSingleShot(true);
  13.     tapTimer.setInterval(1000);
  14.     powerOffTimer.setSingleShot(true);
  15.  
  16.     wiringPiISR(3,INT_EDGE_BOTH,handleEdgeBoth);
  17.     //wiringPiISR(3,INT_EDGE_RISING,handleEdgeRisingInterrupt);
  18.  
  19.     connect(&tapTimer,SIGNAL(timeout()),this,SLOT(tapTimeout(void)),Qt::QueuedConnection);
  20.     instance=this;
  21. }
  22. void PowerControl::handleEdgeBoth()
  23. {
  24.     PowerControl *pc = getInstance();
  25.     unsigned long now = millis();
  26.     unsigned long elapsedTime = now - lastTime;
  27.     lastTime = now;
  28.  
  29.  
  30.     qDebug() << "Elapsed time =" << elapsedTime;
  31.  
  32.     if (elapsedTime < DEBOUNCE_TIME)
  33.     {
  34.  
  35.         qDebug() << "key bounce detected\n";
  36.         return;
  37.     }
  38.     else
  39.         emit pc->edgeDetected(digitalRead(3));
  40.  
  41.  
  42.  
  43. }
  44. void PowerControl::handleIrq(bool afterEdgeState)
  45. {
  46.     if (afterEdgeState)
  47.         qDebug() << "Rising Edge Detected";
  48.     else
  49.         qDebug() << "Falling Edge Detected";
  50. }
  51. void PowerControl::edgeDetected(bool edge)
  52. {
  53.     if (edge)
  54.     {
  55.         qDebug() << "Rising Edge Detected";
  56.         tapTimer.stop();
  57.     }
  58.     else
  59.     {
  60.         QTimer::singleShot(1000, this, SLOT(tapTimeout(void)));
  61.  
  62.         tapTimer.start();
  63.         qDebug() << "Falling Edge Detected, timer isActive = " << tapTimer.isActive();
  64.     }
  65. }
  66.  
  67. PowerControl::~PowerControl()
  68. {
  69.  
  70. }
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Hardware is Rpi Zero W, Qt 4.8 running on Stretch Lite

Thanks!