/**
* Updates the basic gesture recognizer. This performs instantaneous pose recognition, and also some low pass filtering to promote
* stability.
*/
void MicroBitAccelerometer::updateGesture()
{
// Check for High/Low G force events - typically impulses, impacts etc.
// Again, during such spikes, these event take priority of the posture of the device.
// For these events, we don't perform any low pass filtering.
int force = instantaneousAccelerationSquared();
if (force > MICROBIT_ACCELEROMETER_3G_THRESHOLD)
{
if (force > MICROBIT_ACCELEROMETER_3G_THRESHOLD && !shake.impulse_3)
{
MicroBitEvent e(MICROBIT_ID_GESTURE, MICROBIT_ACCELEROMETER_EVT_3G);
shake.impulse_3 = 1;
}
if (force > MICROBIT_ACCELEROMETER_6G_THRESHOLD && !shake.impulse_6)
{
MicroBitEvent e(MICROBIT_ID_GESTURE, MICROBIT_ACCELEROMETER_EVT_6G);
shake.impulse_6 = 1;
}
if (force > MICROBIT_ACCELEROMETER_8G_THRESHOLD && !shake.impulse_8)
{
MicroBitEvent e(MICROBIT_ID_GESTURE, MICROBIT_ACCELEROMETER_EVT_8G);
shake.impulse_8 = 1;
}
impulseSigma = 0;
}
// Reset the impulse event onve the acceleration has subsided.
if (impulseSigma < MICROBIT_ACCELEROMETER_GESTURE_DAMPING)
impulseSigma++;
else
shake.impulse_3 = shake.impulse_6 = shake.impulse_8 = 0;
// Determine what it looks like we're doing based on the latest sample...
uint16_t g = instantaneousPosture();
// Perform some low pass filtering to reduce jitter from any detected effects
if (g == currentGesture)
{
if (sigma < MICROBIT_ACCELEROMETER_GESTURE_DAMPING)
sigma++;
}
else
{
currentGesture = g;
sigma = 0;
}
// If we've reached threshold, update our record and raise the relevant event...
if (currentGesture != lastGesture && sigma >= MICROBIT_ACCELEROMETER_GESTURE_DAMPING)
{
lastGesture = currentGesture;
MicroBitEvent e(MICROBIT_ID_GESTURE, lastGesture);
}
}
/**
* Service function.
* Determines a 'best guess' posture of the device based on instantaneous data.
*
* This makes no use of historic data, and forms the input to the filter implemented in updateGesture().
*
* @return A 'best guess' of the current posture of the device, based on instanataneous data.
*/
uint16_t MicroBitAccelerometer::instantaneousPosture()
{
bool shakeDetected = false;
// Test for shake events.
// We detect a shake by measuring zero crossings in each axis. In other words, if we see a strong acceleration to the left followed by
// a strong acceleration to the right, then we can infer a shake. Similarly, we can do this for each axis (left/right, up/down, in/out).
//
// If we see enough zero crossings in succession (MICROBIT_ACCELEROMETER_SHAKE_COUNT_THRESHOLD), then we decide that the device
// has been shaken.
if ((getX() < -MICROBIT_ACCELEROMETER_SHAKE_TOLERANCE && shake.x) || (getX() > MICROBIT_ACCELEROMETER_SHAKE_TOLERANCE && !shake.x))
{
shakeDetected = true;
shake.x = !shake.x;
}
if ((getY() < -MICROBIT_ACCELEROMETER_SHAKE_TOLERANCE && shake.y) || (getY() > MICROBIT_ACCELEROMETER_SHAKE_TOLERANCE && !shake.y))
{
shakeDetected = true;
shake.y = !shake.y;
}
if ((getZ() < -MICROBIT_ACCELEROMETER_SHAKE_TOLERANCE && shake.z) || (getZ() > MICROBIT_ACCELEROMETER_SHAKE_TOLERANCE && !shake.z))
{
shakeDetected = true;
shake.z = !shake.z;
}
// If we detected a zero crossing in this sample period, count this.
if (shakeDetected && shake.count < MICROBIT_ACCELEROMETER_SHAKE_COUNT_THRESHOLD)
{
shake.count++;
if (shake.count == 1)
shake.timer = 0;
if (shake.count == MICROBIT_ACCELEROMETER_SHAKE_COUNT_THRESHOLD)
{
shake.shaken = 1;
shake.timer = 0;
return MICROBIT_ACCELEROMETER_EVT_SHAKE;
}
}
// measure how long we have been detecting a SHAKE event.
if (shake.count > 0)
{
shake.timer++;
// If we've issued a SHAKE event already, and sufficient time has assed, allow another SHAKE event to be issued.
if (shake.shaken && shake.timer >= MICROBIT_ACCELEROMETER_SHAKE_RTX)
{
shake.shaken = 0;
shake.timer = 0;
shake.count = 0;
}
// Decay our count of zero crossings over time. We don't want them to accumulate if the user performs slow moving motions.
else if (!shake.shaken && shake.timer >= MICROBIT_ACCELEROMETER_SHAKE_DAMPING)
{
shake.timer = 0;
if (shake.count > 0)
shake.count--;
}
}
if (instantaneousAccelerationSquared() < MICROBIT_ACCELEROMETER_FREEFALL_THRESHOLD)
return MICROBIT_ACCELEROMETER_EVT_FREEFALL;
// Determine our posture.
if (getX() < (-1000 + MICROBIT_ACCELEROMETER_TILT_TOLERANCE))
return MICROBIT_ACCELEROMETER_EVT_TILT_LEFT;
if (getX() > (1000 - MICROBIT_ACCELEROMETER_TILT_TOLERANCE))
return MICROBIT_ACCELEROMETER_EVT_TILT_RIGHT;
if (getY() < (-1000 + MICROBIT_ACCELEROMETER_TILT_TOLERANCE))
return MICROBIT_ACCELEROMETER_EVT_TILT_DOWN;
if (getY() > (1000 - MICROBIT_ACCELEROMETER_TILT_TOLERANCE))
return MICROBIT_ACCELEROMETER_EVT_TILT_UP;
if (getZ() < (-1000 + MICROBIT_ACCELEROMETER_TILT_TOLERANCE))
return MICROBIT_ACCELEROMETER_EVT_FACE_UP;
if (getZ() > (1000 - MICROBIT_ACCELEROMETER_TILT_TOLERANCE))
return MICROBIT_ACCELEROMETER_EVT_FACE_DOWN;
return MICROBIT_ACCELEROMETER_EVT_NONE;
}
/**
* Service function.
* Determines a 'best guess' posture of the device based on instantaneous data.
*
* This makes no use of historic data, and forms the input to the filter implemented in updateGesture().
*
* @return A 'best guess' of the current posture of the device, based on instanataneous data.
*/
uint16_t MicroBitAccelerometer::instantaneousPosture()
{
bool shakeDetected = false;
// Test for shake events.
// We detect a shake by measuring zero crossings in each axis. In other words, if we see a strong acceleration to the left followed by
// a strong acceleration to the right, then we can infer a shake. Similarly, we can do this for each axis (left/right, up/down, in/out).
//
// If we see enough zero crossings in succession (MICROBIT_ACCELEROMETER_SHAKE_COUNT_THRESHOLD), then we decide that the device
// has been shaken.
if ((getX() < -MICROBIT_ACCELEROMETER_SHAKE_TOLERANCE && shake.x) || (getX() > MICROBIT_ACCELEROMETER_SHAKE_TOLERANCE && !shake.x))
{
shakeDetected = true;
shake.x = !shake.x;
}
if ((getY() < -MICROBIT_ACCELEROMETER_SHAKE_TOLERANCE && shake.y) || (getY() > MICROBIT_ACCELEROMETER_SHAKE_TOLERANCE && !shake.y))
{
shakeDetected = true;
shake.y = !shake.y;
}
if ((getZ() < -MICROBIT_ACCELEROMETER_SHAKE_TOLERANCE && shake.z) || (getZ() > MICROBIT_ACCELEROMETER_SHAKE_TOLERANCE && !shake.z))
{
shakeDetected = true;
shake.z = !shake.z;
}
if (shakeDetected && shake.count < MICROBIT_ACCELEROMETER_SHAKE_COUNT_THRESHOLD && ++shake.count == MICROBIT_ACCELEROMETER_SHAKE_COUNT_THRESHOLD)
shake.shaken = 1;
if (++shake.timer >= MICROBIT_ACCELEROMETER_SHAKE_DAMPING)
{
shake.timer = 0;
if (shake.count > 0)
{
if(--shake.count == 0)
shake.shaken = 0;
}
}
// Shake events take the highest priority, as under high levels of change, other events
// are likely to be transient.
if (shake.shaken)
return MICROBIT_ACCELEROMETER_EVT_SHAKE;
if (instantaneousAccelerationSquared() < MICROBIT_ACCELEROMETER_FREEFALL_THRESHOLD)
return MICROBIT_ACCELEROMETER_EVT_FREEFALL;
// Determine our posture.
if (getX() < (-1000 + MICROBIT_ACCELEROMETER_TILT_TOLERANCE))
return MICROBIT_ACCELEROMETER_EVT_TILT_LEFT;
if (getX() > (1000 - MICROBIT_ACCELEROMETER_TILT_TOLERANCE))
return MICROBIT_ACCELEROMETER_EVT_TILT_RIGHT;
if (getY() < (-1000 + MICROBIT_ACCELEROMETER_TILT_TOLERANCE))
return MICROBIT_ACCELEROMETER_EVT_TILT_DOWN;
if (getY() > (1000 - MICROBIT_ACCELEROMETER_TILT_TOLERANCE))
return MICROBIT_ACCELEROMETER_EVT_TILT_UP;
if (getZ() < (-1000 + MICROBIT_ACCELEROMETER_TILT_TOLERANCE))
return MICROBIT_ACCELEROMETER_EVT_FACE_UP;
if (getZ() > (1000 - MICROBIT_ACCELEROMETER_TILT_TOLERANCE))
return MICROBIT_ACCELEROMETER_EVT_FACE_DOWN;
return MICROBIT_ACCELEROMETER_EVT_NONE;
}