On Tue, 29 Aug 2017 23:01:16 -0400 harinath Nampally <harinath...@gmail.com> wrote:
> > We should never say "transient is for rising > > direction" or "ff_mt is for falling direction". any combination is fine. > > Ok I agree that there is no hard and fast rule that "transient is for rising > direction" or "ff_mt is for falling direction". > But in our case, datasheet for these chips define these events based on > acceleration magnitude rising or falling below a set threshold value. > > For quick reference, below excerpts are from fxls8471 datasheet: > Motion Event: "When the acceleration exceeds a set threshold for a set > amount of time, > the motion interrupt is asserted." > > Freefall event: "The detection of “Freefall” involves the monitoring > of the X, Y, and Z axes > for the condition where the acceleration magnitude is below a > user-specified threshold > for a user-definable amount of time" > > Transient event: "When the high-pass filter is bypassed, the > functionality becomes > similar to the motion-detection function; in this mode, acceleration > greater than > a programmable threshold is detected (along an axis)." > > Therefore I think in this driver freefall event is defined as > 'falling' event type and > motion event is defined as 'rising' event type and Transient is also defined > as > 'rising' event type. > As you might already know that mma8562 and mma8563 doesn't have > transient event support > but they do have freefall and motion event support which are defined > as 'fall' and 'rise' > event types respectively. Please note in this driver, motion event is > enabled/configured only > for mma8652 and mma8653. > Therefore if I read/write sysfs node for 'rise' it should use the > FF_MT registers for mma8652 and mma853, but for all others like > mma8451, mma8452 and > mma8453 which has transient event support it picks the Transient > registers if enabled. Also please > note transient event is enabled(but not motion event) for mma8451, > mma8452 and mma8453. > The problem seems like we have two different events(motion and > transient) that are defined > as same event type 'rising' but in fact both motion and transient are > pretty much similar as they > both raise interrupt flag when the acceleration magnitude rises above > the threshold. > Only difference is transient event has its own event config registers > with High pass filter. > If HPF bypassed using config register transient event acts like motion > detection event. > > That was my understanding but please correct me if I am wrong. I agree with your understanding. It's a rising threshold, just that the input will only reflect high frequency changes in the signal. > > > Only freefall mode needs one fix: remembering to which set of registers to > > fall back when > > disabling it. > > I don't quite understand what you mean by 'to fall back when disabling > it'. Please elaborate. I would > appreciate if you could suggest your logic in the form of pseudo-code. > Thanks for your time > ...
