3.9.1 Frequency Hop

Operation

The Frequency Hop feature varies the touch measurement frequency between consecutive measurements. Response time slightly increases with Frequency Hop enabled. A typical increase in response time would be one Measurement Period. Refer to the Response Time for more information.

The three frequencies to acquire touch are pre-defined by the host. Refer to the Hop Frequency (FREQ) register. The MTCH2120 user has complete control over the used frequencies. During run-time, the host can change these frequencies.

Note: In Low-Power mode, Frequency Hoping (and, if recommended, oversampling along with it) is deactivated.

Initialization

The Frequency Hop feature is enabled by writing 1 to FREQHOP bit the Device Control (DEVCTRL) register. The three frequencies must be defined in FREQ[n] registers.

Enabling or disabling these features by the Host does not require a reset after the configuration update. Refer to the Configuration Summary for more details.

Steps to Configure Frequency Hop

  1. Different frequencies can be selected by writing in the FREQ[n] register. Frequencies will be taken into effect from the following measurement. Refer to the Frequency Hop for details on the possible values and offset address.
    Note: The Autotune feature must be disabled before writing the register. See section 3.8.2.
  2. The Frequency Hop feature is enabled by writing 1 in DEVCTRL.FREQHOP register.
  3. Save the Settings (optional):
    Note: Use the "save" command to apply the updated configuration after resetting the device. Otherwise, this step is optional.
    • Write 1 in DEVCTRL.SAVE to save the configuration