stmpe16m31 STMicroelectronics, stmpe16m31 Datasheet - Page 59

• Manufacturer Part Number: stmpe16m31
• Description: S-touch? 16/24-channel Touchkey Controller With Pwm And Ratio Engines
• Manufacturer: STMicroelectronics

STMPE16M31, STMPE24M31
13.6
Definition of data accessible through channel data register
Table 14.
Locked impedance
Data name
Channel delay
Impedance
Impedance
Calibrated
Types of data accessible through the channel data register
EVR
TVR
EVR (environmental variance register) is a threshold defined by system, of
TVR (touch variance register) is a threshold defined by system, of which, if
the sense impedance changed by a magnitude more than the associated
TVR, this channel is considered touched. The result of this comparison is
directly accessible in the TOUCH_DET register.
which, if the sensed impedance changed by a magnitude less than the
associated EVR, this is considered an environmental change and the device
will calibrate the internal reference (calibrated impedance) accordingly.
Channel delay is used to tune the individual channel into effective
measurement range. This field is 6-bit (0-63). Each bit in this field represents
approximately 0.5 pF capacitance.
This field is a real time reflection of impedance measured at the
corresponding channel. As capacitance is inversely proportional to
impedance, this field reduces in value when capacitance on the channel
increases.
This field is of 13-bit length. The least significant 4 bits are results of internal
processing and should not be used. The actual impedance data could be
obtained by shifting the [Impedance] 4 bits to the right.
Read-only
This field contains an internal reference used by the device to decide whether
a touch has occurred. This value is adjusted regularly (calibration) by the
device automatically.
Data in this field is similar to data in impedance field, except that once this
data type is chosen, the device maintains a complete set of impedance data
in this field and stop refreshing it.
This is useful for the application where it is required that all impedance data
are sampled within a very short time.
Doc ID 16174 Rev 3
Definition
Touch sensor controller
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