AN2855 Application note Configuration for single-click and double-click detection using the FC30 Introduction This document is intended to provide application 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. February 2009 Rev 1 1/8 www.st.com Contents AN2855 Contents 1 2 3 2/8 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 Power-down mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1 Entering power-down mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2 Exiting power-down mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 AN2855 1 Theory of operation 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 operating 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 enabled through specific commands sent to the device over the I2C bus that is available through dedicated pins (Figure 1). FC30 pinout - I2C pins for click recognition mode Vdd Vdd_IO 1 6 10uF 8 SCL SDA SIGN PD 13 LC 100nF Top VIEW PC Figure 1. GND Digital signal from/to signal controller.Signal’s levels are defined by proper selection of Vdd_IO AM03290v1 3/8 Theory of operation 1.2 AN2855 Entering single click recognition mode To enable the single-click recognition function, the device must first be configured for powerdown mode driving PD pin to GND. Then the following sequence of commands must be sent to the device through I2C 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 singleclick recognition mode and orientation detection is no longer active. 1.3 Entering double-click recognition mode As with single-click recognition, to enable the 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 I2C 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); 4/8 AN2855 Theory of operation 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. 5/8 Power-down mode 2 AN2855 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 power-down mode. Power-down mode is still available through dedicated I2C commands. 2.1 Entering power-down mode To enter the power-down mode, send the following I2C command to the device: I2C_Write(0x1D, 0x20h, 0x00h); 2.2 Exiting power-down mode To exit the power-down mode, send the following I2C command to the device: I2C_Write(0x1D, 0x20h, 0x47h); 6/8 AN2855 3 Revision history Revision history Table 1. Document revision history Date Revision 17-Feb-2009 1 Changes Initial release. 7/8 AN2855 Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST’s terms and conditions of sale. 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