february 2009 rev 1 1/8 AN2855 application note configuration for single-click and double-click detection using the fc30 introduction this document is intended to provide applic ation information for the click and double-click detection functions of the fc30. when a single or double mechanical tap is detected, the fc30 provides an interrupt signal, enabling a ?mouse button-like? function for intuitive man-machine interface solutions. a power-down mode selectable through a dedicated command ensures very low current consumption in battery-operated devices. www.st.com
contents AN2855 2/8 contents 1 theory of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 device pinout for click recognition mode . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 entering single click recognition mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.3 entering double-click recognition mode . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.4 exiting click recognition mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 power-down mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1 entering power-down mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2 exiting power-down mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
AN2855 theory of operation 3/8 1 theory of operation the click recognition function featured in the fc30 helps to create a man-machine interface with little software loading. the device can be configured to output an interrupt signal on a dedicated pin when tapped in any direction. if the sensor is exposed to a single input stimulus, it generates an interrupt request on inertial interrupt pin pc. a more advanced feature allows the generation of an interrupt request when a double input stimulus with fixed time between the two events is recognized, enabling a mouse button-like functionality. note: while the device is operat ing in click/double -click recognition mode, the orientation detection function is not available. 1.1 device pinout for click recognition mode click recognition mode is enable d through specific commands se nt to the device over the i 2 c bus that is available through dedicated pins ( figure 1 ). figure 1. fc30 pinout - i 2 c pins for click recognition mode 6 8 1 3 1 top view 10 u f vdd 100nf gnd vdd_io sign pc lc digit a l s ign a l from/to s ign a l controller.sign a l? s level sa re defined b yproper s election of vdd_io pd scl sda am0 3 290v1
theory of operation AN2855 4/8 1.2 entering single click recognition mode to enable the single-click recognition function, the device must first be configured for power- down mode driving pd pin to gnd. then the following sequence of commands must be sent to the device through i 2 c bus: i2c_read(0x5d, 0x16, value_1); i2c_write(0x5d, 0x16, value_1 & 0x1f); i2c_write(0x1d, 0x3bh, 0x77h); i2c_write(0x1d, 0x3ch, 0x07h); i2c_write(0x1d, 0x3dh, 0xfeh); i2c_write(0x1d, 0x3eh, 0x10h); i2c_write(0x1d, 0x3fh, 0xffh); i2c_write(0x1d, 0x38h, 0x15h); i2c_write(0x1d, 0x20h, 0x47h); i2c_write(0x1d, 0x22h, 0x07h); where i2c_read and i2c_write have the following syntax: i2c_read(slaveaddress, subaddress, destinationvalue); i2c_write(slaveaddress, subaddress, sourcevalue); at the end of the sequence the device will be in a power on state, ready to operate in single- click recognition mode and orientation detection is no longer active. 1.3 entering double-click recognition mode as with single-click recognition, to enable t he double-click recognition function the device must be first configured for power-down mode driving pd pin to gnd. then the following sequence of commands must be sent to the device through i 2 c bus: i2c_read(0x5d, 0x16, value_1); i2c_write(0x5d, 0x16, value_1 & 0x1f); i2c_write(0x1d, 0x3bh, 0x77h); i2c_write(0x1d, 0x3ch, 0x07h); i2c_write(0x1d, 0x3dh, 0xfeh); i2c_write(0x1d, 0x3eh, 0x10h); i2c_write(0x1d, 0x3fh, 0xffh); i2c_write(0x1d, 0x38h, 0x2ah); i2c_write(0x1d, 0x20h, 0x47h); i2c_write(0x1d, 0x22h, 0x07h);
AN2855 theory of operation 5/8 at the end of the sequence, the device will be in a power on state, ready to operate in double-click recognition mode and orientation detection is no longer active. 1.4 exiting click recognition mode to exit from the click recognition function and restore the orientation detection, the device must be first be turned off by switching off the power supply, then turned on.
power-down mode AN2855 6/8 2 power-down mode when the fc30 is operating in click or double-click recognition mode, the pd pin must be tied to gnd and no longer enabling the po wer-down mode. power-down mode is still available through dedicated i 2 c commands. 2.1 entering power-down mode to enter the power-down mode, send the following i 2 c command to the device: i2c_write(0x1d, 0x20h, 0x00h); 2.2 exiting power-down mode to exit the power-down mode, send the following i 2 c command to the device: i2c_write(0x1d, 0x20h, 0x47h);
AN2855 revision history 7/8 3 revision history table 1. document revision history date revision changes 17-feb-2009 1 initial release.
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