mTouch® Low-Power Configuration

Last modified by Microchip on 2023/11/09 08:55

Power consumption remains an important factor in the design of any system. To reduce power consumption, the device will switch from normal mode to low-power mode if no touch is detected for the inactive timeout period. In low-power mode, only selected sensors will be scanned and if the sensor reading on any of the selected sensors is more than the threshold value, the device will switch back to normal mode. During low-power mode, the device will be put in standby sleep between measurements to save power. The mTouch® library supports selecting configurations for low-power mode and selecting sensors that need to be scanned periodically during low-power mode. The mode switching logic is implemented inside the mTouch library and APIs are provided to access the low-power mode. The flow chart detailing the two modes of operation is shown in the accompanying image.

Flowchart showing the two modes of operation: Normal and Low Power

Low-power Configuration

The low-power configuration consists of:

  • Low-power Measurement Enable
  • Low-power Measurement Period
  • Low-power Detect Threshold
  • Touch Inactivity Timeout
  • Baseline Update Period
  • Low-power Measurement Sensor Selection

Low Power measurement settings in the GUI Low Power tab

Back to Top

Enable Low Power Measurement Period

The Enable Low Power Measurement checkbox needs to be checked for enabling the automatic power mode switching between normal power mode and low-power mode. Uncheck to disable the power mode switching.

Low-power Measurement Period

The Low-power Measurement Period determines the interval between low-power touch measurement. On checking the Enable Low Power Measurement checkbox, the Low-power Measurement Period combo box will be enabled allowing you to select the period from the combo box.

Low-power Detect Threshold

Sensor Low-power Detect Threshold during low-power measurement mode is used to trigger the switch to normal mode. During low-power measurement, if any of the readings cross the detect threshold, the mode will be switched to normal mode. The moment when the system enters low-power mode, the last sensor reading becomes the setpoint for the sensor and then the sensor's current reading will be compared to this setpoint as shown in the accompanying image.

Graph of sensor reading showing where reading exceeds detection threshold triggering return to Normal mode operation

Touch Inactivity Timeout

Touch Inactivity Timeout refers to the waiting time (in milliseconds) for the application to switch to low-power measurement after the last touch.

Baseline Update Period

During low-power measurement, it is recommended to perform a periodic active measurement to perform a baseline update, the Baseline Update Period. This parameter defines the measurement interval (in milliseconds) to perform drifting. It is recommended to configure this parameter to be more than the low-power period. A value of zero means baseline update is disabled during low-power measurement.

Low-Power Measurement Sensor Selection

The sensors that need to be scanned during low-power mode should be selected from the Sensor Settings page of individual sensors. The Scan on Low Power Mode Enable checkbox in the Sensor Settings needs to be checked to add the sensor to the list of selected sensors for low-power measurement. At least one of the sensors should be selected for low-power measurement.

Sensor settings tab on GUI is where you select which sensors are scanned in Low Power mode

Back to Top