Sensors

Freescale Semiconductor, Inc.

12

MMA7660FC

Orientation Detection

Orientation Detection Logic

MMA7660FC gives the customer the capability to do orientation detection for such applications as Portrait/Landscape in

Mobile Phone/PDA/ PMP. The tilt orientation of the device is in 3 dimensions and is identified in its last known static position. This

enables a product to set its display orientation appropriately to either portrait/landscape mode, or to turn off the display if the

product is placed upside down. The sensor provides six different positions including: Left, Right, Up, Down, Back, and Front,

shown in Table 7. In Active Mode the data is processed and updates the orientation positions in the TILT (0x03) register. At each

measurement interval, it computes new values for Left, Right, Up, Down, Back, and Front but it does not automatically update

these bits in the TILT (0x03) register. These values are updated depending on the debounce filter settings (SR Register 0x08)

configured by the customer.

In order to give the customer the ability to configure the debounce filter, specific to there application, they can change the

following bits in the SR (0x08) register, FILT [2:0]. Please see below for a more detailed explanation of how the FILT [2:0] works

in conjunction with updating the TILT (0x03) register:

•

If FILT [2:0] = 000, then the new values for Left, Right, Up, Down, Back, and Front are updated in the TILT (0x03) register

(PoLa [2:0] and BaFro [1:0]) after every reading without any further analysis.

•

If FILT [2:0] = 001 – 111, then the sensor requires the computed values for Left, Right, Up, Down, Back, and Front to be the

same from 1-7 consecutive readings (depending on the value in FILT [2:0], before updating the values stored in TILT (0x03)

register (PoLa [2:0] and BaFro [1:0]). The debounce counter is reset after a mismatched reading or the TILT (0x03) register

is updated (if the orientation condition is met).

Figure 6. Orientation Detection Logic in 3-Dimensional Space

Table 7. Orientation Detection Logic of when Interrupt will Occur

Orientation

Xg

Yg

Zg

Shake

|X| > +1.3g

or

|Y| > +1.3g

or

|Z| > +1.3g

Up

|Z| < 0.8g and |X| > |Y| and X < 0

Down

|Z| < 0.8g and |X| > |Y| and X > 0

Right

|Z| < 0.8g and |Y| > |X| and Y < 0

Left

|Z| < 0.8g and |Y| > |X| and Y > 0

Back

Z < -0.25g

Front

Z > 0.25g

Down

Up

Front

Back

Right

Left

Down

Up

Front

Back

Right

Left