In EKF3, framesSincePredict in NavEKF3_core::readIMUData(), only exits in the following two lines:
// Keep track of the number of IMU frames since the last state prediction
// reset the counter used to let the frontend know how many frames have elapsed since we started a new update cycle
framesSincePredict = 0;
Beyond that two lines, no code has used it, so the questions is why it is still exits? It seems that it does not have any actual use.
p.s.: I know in EKF2, it is used as counter to down sample.
Well, I have seen that :
// report the number of frames lapsed since the last state prediction
// this is used by other instances to level load
uint8_t NavEKF3_core::getFramesSincePredict(void) const
So it is still useful.