3.2.2 Initialization

In the default configuration, buttons 0 to 11 are enabled. A device reset is required to reflect register modifications. Refer to Configuration Summary for more details.

Enable/Disable

Buttons can be enabled (or disabled) by writing a 1 (or 0) to the Enable (EN) bit in the Sensor Control (SENCTRL) register. This configuration update will not reflect immediately. It will reflect after the device reset (it could be either a software or hardware reset).

Steps to Enable/Disable Buttons

  1. Write 1 or 0 bit in SENCTRL[n].EN register to enable or disable the button.
  2. Write 1 in DEVCTRL.SAVE register to save the configuration.
  3. Write 1 in DEVCTRL.RESET to reset the device.

Unused Button Pins

To minimize power consumption:
  • Unused buttons should be disabled. Refer to Steps to Enable/Disable buttons
  • The pin should be left unconnected

Configuring the unused button's pin as GPIO output-LOW improves the noise immunity. Refer to GPIO Host Communication sections to configuring the pin as output-LOW.

Suspend

Buttons can be suspended by writing a 1 to the Suspend (SUSPEND) bit in the Sensor Control (SENCTRL) register.
Note: If the SUSPEND configuration is stored in memory, this bit is ignored during power up. All the enabled sensors will be measured immediately after power-up. If the Host wants to suspend a sensor, it must give a command again through the Inter-Integrated Circuit (I2C).

Calibrate

Calibration is a process of compensating for the environmental conditions like humidity or temperature that impact sensor capacitance. During power-up, MTCH2120 performs calibration. After power-up calibration, further changes in environmental conditions are taken care of by the drifting feature explained in the Drift Operation section. Additionally, it is possible to calibrate a particular sensor or all sensors through an I2C interface. For example, it is recommended to recalibrate a sensor if it is suspended for some period in which it may have experienced environmental changes.

Calibration for a button can be triggered by 1 to the Calibrate (CAL) bit in the Sensor Control (SENCTRL) register. And the calibration will happen in the next measurement cycle.