SFH7770E6 datasheet(21/33 Pages) OSRAM

21 / 33 page

Measure

Signals

PS1, PS2,

PS3

Initialization

Wait 10 ms

PS1 >80 or

PS2 >80 or

PS3 >80 ?

YES

PS3: max signal

and

PS1: min signal

YES

Event

detected:

„move left“

PS1: max signal

and

PS3: min signal

YES

Event

detected:

„move right“

PS2: min signal

Event

detected:

„move down“

PS2: max signal

Event

detected:

„move up“

YES

Fig. 19: Gesture recognition sample flow for

SFH 7770 E6 and 3 LEDs.

Fig.

18:

Sample

setup

for

gesture

recognition

with

SFH

7770

E6,

each

comprising 3 LEDs.

detected by evaluating the relative signal

height of LEDs 1, 2 and 3.

A flowchart how to derive the direction of the

hand movement is presented in Fig. 19. The

operating principle of the flow is as follows:

1) Readout of all PS channels every 10ms.

A repeat rate of 10ms is the fastest possible

measurement rate for the proximity sensor.

The actual measurement of all three

proximity channels occurs within 1 ms to 2

ms (depending on the PS integration time

setting, i.e. after all three LED bursts are

finished). The PS data are then available

and accessible via the I²C bus. The total

minimum time delay is here 1 ms.

2) Check if a least one PS signal (channel 1,

2 or 3) is above a given threshold.

In order to eliminate unwanted response of

the sensor to noise, the signal value must

be above a fixed threshold level. A suitable

level has to be determined for each

application separately. Typical levels are

~80-100 output counts of the proximity

sensor.

3) Determine which channel has the

maximum and minimum signal values

The minimum and maximum evaluation is

only done if at least one of the considered

proximity signals is above the threshold

level.

Otherwise,

new

proximity

measurement is initiated.

February 27, 2012

page 21 of 33

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