QTouch®, mTouch® Solution Terminology

This table is based on QTouch v5.0 and mTouch v2.5.

Parameter Categories Parameter Description Parameter Name in QTouch® Configurable in Atmel START Parameter Name in mTouch® Configurable in MCC Additional Details
Touch Basic Terms Sensor acquisition value Signal No Reading No
Reference value used for touch detection Reference No Baseline No
Difference between acquisition and reference Delta No Deviation No
State of touch detection Detect No Pressed No
Measurement technique Dual-slope measurement No Differential CVD No
Sensor Definitions Key sensor which reports ON/OFF status Button Yes Button Yes
Linear touch sensor Slider Yes Slider Yes
Angular touch sensor Wheel Yes Wheel Yes
Proximity sensor Button with high gain Yes Proximity Yes Proximity could be created by configuring a button with high gain and driven shield in QTouch. No specific configuration settings available.
Sensor Technology Self-capacitance sensor Selfcap Yes sensor Yes Requires one Y-line sense pin per button.
Mutual capacitance sensor Mutualcap Yes Not Available No Requires one X-line drive pin and one Y-line sense pin per button.
Sensor Acquisition Parameters Touch measurement periodicity Scan rate Yes Scan Rate Yes MCC mTouch configurator has options to control the scan rate using TMR1 and scan the sensor in free runing mode.
Touch measurement frequency Acquisition frequency Yes Not Available No
Sensor acquisition interrupt priority PTC interrupt priority Yes Not Available No PTC interrupt priority only applicable on SAM devices.
Button Configuration Parameters Sensor's detect threshold Sensor detect threshold Yes Threshold Yes
Sensor's out-of-detect threshold Sensor detect hysteresis Yes Sensor detect hysteresis Yes
Group selection for adjacent key suppression AKS group Yes AKS group Yes AKS can be used when touching multiple sensors is not allowed in a system.
Method selection for button status update Not Available No Interface method Yes Callback or polling needs to be used to notify/update application.
Slider/Wheel Configuration Parameters No. of segments in a slider/wheel No. of buttons Yes No. of Segments Yes
No. of unique positions reported by the slider/wheel Resolution Yes Resolution Yes
Inactive area on both ends of the slider Dead band Percentage Yes Dead band Percentage Yes
No. of positions you have to move before the touch position is reported Position hysterisis Yes Position hysterisis Yes
Slider/wheel detect threshold Threshold Yes Threshold Yes
Proximity Configuration Parameters Gain for deviation integration filter Not Applicable No Deviation integration filter: gain Yes
Enable median filter Not Applicable No Median filter Yes
Window for median filter Not Applicable No Median filter: window Yes
Sensor Node Parameters Pin selection Y-line, X-line Yes Pin Yes Mutual capactiance sensor requires one X-line drive pin and one Y-line sense pin per button.
Acquisition clock prescaler Prescaler for PTC Yes Not Available No MCC mTouch configurator will calcualte the prescaler for ADC based on Fosc auotmatically.
Internal series resistor selection Series resistor Yes Not Available No
Gain setting for touch signal/reading Digital/analog gain Yes Not Available No
IIR filter for touch signal/reading Not Available No Reading filtering: level No In mTouch, new reading is updated as ((oldreading-(oldreading»filter level))+(rawsample»filter level)).
Gain setting for touch reference/baseline Not Available Yes Baseline filtering: gain Yes In mTouch, new baseline is updated as ((oldbaseline-(oldbaseline»gain))+reading).
Scaling for deviation Not Available No Deviation scaling Yes In mTouch, the devaition value is calculated as ((reading - baseline)»scaling).
Number of samples taken for each measurement Filter level Yes Oversample Yes
Sensor charging time Charge share delay (CSD) Yes Precharge time Yes CSD indicates the number of additional cycles that are inserted within a touch measurement cycle. Precharge time is the amount of time spent charging the internal and external capacitors.
Settling time delay Not Applicable No Acquisition time Yes Acquisition time is the amount of time spent allowing the capacitors to equalize to a median voltage after being precharged to opposite states.
Additional internal capacitance to the sensor nodes Not Available No Additional sample capacitance Yes This is used to improve the match between internal and external capacitance for a better sensing performance.
Sensor Configuration Parameters Enable auto-calibration Sensor charge time auto-tune Yes Auto-calibration Yes For AVR devices, enabling this setting will automatically set the number of additional charge cycles needed to ensure full charging of the touch sensor. For SAM devices, enabling this setting will automatically set the pre-scaler setting needed to ensure full charging of the touch sensor. For PIC devices with HCVD, enabling this setting will automatically set acquisition time and additional internal capacitor. When the option is disabled, you need to manually set these parameters and ensure full charge transfer of the touch sensor.
Enable noise performance improvement and water tolerance Enable driven shield Yes Driven shield Yes Both QTouch and mTouch can assign a dedicated driven shield pin. Having a dedicated shield improves both noise performance and water tolerance. PTC devices, PIC16LF156x and ADCC devices can drive none-scanning sensors as the shield, which improves water tolerance.
Sensor Touch Parameters No. of additional touch measurements to confirm touch Detect integration (DI) Yes Deboucne Yes
No. of additional touch measurements to confirm an out-of-touch detection Away from touch detect integration Yes Deboucne Yes
Threshold for out-of-touch recalibration Away from touch recalibration threshold Yes Negative threshold No Negative threshold is configurable in mTouch code and not in MCC.
No. of additional touch measurements to confirm out-of-touch recalibration Not Available No Consecutive decodes Yes
Rate of change of reference (baseline) for positive delta (deviation) Towards touch drift rate Yes Baseline filtering: update Yes For QTouch, value is scaled by 200 ms. In mTouch, baseline update is done after this number of sensing cycles.
Rate of change of reference (baseline) for negative delta (deviation) Away from touch drift rate Yes Baseline filtering: update Yes Common value for towards touch and away from touch in mTouch. For QTouch, value is scaled by 200 ms.
Amount of time the change of reference needs to be paused after removing the finger Drift hold time Yes Baseline Hold No Value is scaled by 200 ms for QTouch. This is configurable in the firmware for mTouch.
Re-bursting mode Re-burst mode Yes Re-burst mode Yes
Enable sensor ON timeout Max-ON duration (MOD) Yes Press timeout Yes Set the value of MOD as zero in Atmel START to disable sensor ON timeout in QTouch.
Sensor ON timeout unit Not Available No Press timeout unit Yes In QTouch, unit is time in ms. In mTouch, the unit is main loop task calls by default.
Set maximum sensor ON time/counts Max-ON duration (MOD) Yes Press timeout counts Yes In QTouch, value is scaled by 200 ms.
Frequency Hop Parameters Enable multiple burst frequencies Enable frequency hop Yes Enable AFA Yes Frequency hopping is enabled by default in mTouch.
Enable auto changing of burst frequency Enable frequency auto tuning Yes Automatic frequency adaptation Yes Intelligently choose scan frequency at run-time to avoid noise frequency and its harmonics.
Timer selection for frequency hop Not Available No AFA filter timer Yes The PIC with ADCC doesn't need timer to implement the frequency hoppping.
Number of frequencies used in touch measurement Frequency steps Yes Max/Min Frequency No The mTouch will pick the frequencies in a range, which is configurable in the firmware.
Threshold for noise frequency replacement Maximum variance Yes Noise Threshold No This can be configured in the firmware for mTouch.
Count for noise frequency replacement Tune in count Yes Over Limit Threshold No This can be configured in the firmware for mTouch.
Clock Configuration Settings Oscillator selection Oscillators Yes Oscillator select Yes Select the oscillator from the list.
External clock selection Oscillators No External clock select Yes Select the external clock source from the list if external oscillator is selected.
Internal clock frequency selection Clock settings: prescaler Yes HF internal clock Yes Set the internal clock frequency by selecting the prescaler value.
External clock frequency selection Frequency Yes External clock Yes Enter the external clock frequency if external oscillator is selected.
Clock source prescaler Generic clock generator division Yes Clock divider Yes The internal/external clock selected is divided by this prescaler.
Enable low voltage programming Not Available No Low voltage programming enable Yes
CPU and peripheral clock selection Clock source Yes Not Available No Select the clock generator source for CPU and components from the list in QTouch.
CPU clock divider CPU clock prescaler Yes Not Available No The CPU frequency will be the generic clock selected for CPU divided by the prescaler.
Enable watchdog timer Not Available No Watchdog timer enable Yes
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