QTouch® and mTouch® Solution Terminology

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

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

Parameter CategoriesParameter DescriptionParameter Name in QTouchConfigurable in Atmel STARTParameter Name in mTouchConfigurable in MCCAdditional Details

Touch Basic Terms

Sensor acquisition valueSignalNoReadingNo 
 Reference value used for touch detectionReferenceNoBaselineNo 
 Difference between acquisition and referenceDeltaNoDeviationNo 
 State of touch detectionDetectNoPressedNo 
 Measurement techniqueDual-slope measurementNoDifferential CVDNo 
Sensor DefinitionsKey sensor which reports ON/OFF statusButtonYesButtonYes 
 Linear touch sensorSliderYesSliderYes 
 Angular touch sensorWheelYesWheelYes 
 Proximity sensorButton with high gainYesProximityYesProximity could be created by configuring a button with high gain and driven shield in QTouch. No specific configuration settings are available. 
Sensor TechnologySelf-capacitance sensorSelfcapYessensorYesRequires one Y-line sense pin per button.
 Mutual capacitance sensorMutualcapYesNot AvailableNoRequires one X-line drive pin and one Y-line sense pin per button.
Sensor Acquisition ParametersTouch measurement periodicityScan rateYesScan RateYesMCC mTouch configurator has options to control the scan rate using TMR1 and scan the sensor in free running mode.
 Touch measurement frequencyAcquisition frequencyYesNot AvailableNo 
 Sensor acquisition interrupt priorityPTC interrupt priorityYesNot AvailableNoPTC interrupt priority only applicable on SAM devices.
Button Configuration ParametersSensor's detect thresholdSensor detect thresholdYesThresholdYes 
 Sensor's out-of-detect thresholdSensor detect hysteresisYesSensor detect hysteresisYes 
 Group selection for adjacent key suppressionAKS groupYesAKS groupYesAKS can be used when touching multiple sensors is not allowed in a system.
 Method selection for button status updateNot AvailableNoInterface methodYesCallback or polling needs to be used to notify/update the application.
Slider/Wheel Configuration ParametersNo. of segments in a slider/wheelNo. of buttonsYesNo. of SegmentsYes 
 No. of unique positions reported by the slider/wheelResolutionYesResolutionYes 
 Inactive area on both ends of the sliderDead band PercentageYesDead band PercentageYes 
 No. of positions you have to move before the touch position is reportedPosition hysterisisYesPosition hysterisisYes 
 Slider/wheel detect thresholdThresholdYesThresholdYes 
Proximity Configuration ParametersGain for deviation integration filterNot ApplicableNoDeviation integration filter: gainYes 
 Enable median filterNot ApplicableNoMedian filterYes 
 Window for median filterNot ApplicableNoMedian filter: windowYes 
Sensor Node ParametersPin selectionY-line, X-lineYesPinYesMutual capacitance sensor requires one X-line drive pin and one Y-line sense pin per button.
 Acquisition clock prescalerPrescaler for PTCYesNot AvailableNoMCC mTouch configurator will calculate the prescaler for ADC based on Fosc automatically.
 Internal series resistor selectionSeries resistorYesNot AvailableNo 
 Gain setting for touch signal/readingDigital/analog gainYesNot AvailableNo 
 IIR filter for touch signal/readingNot AvailableNoReading filtering: levelNoIn mTouch, new reading is updated as ((oldreading-(oldreading»filter level))+(rawsample»filter level)).
 Gain setting for touch reference/baselineNot AvailableYesBaseline filtering: gainYesIn mTouch, new baseline is updated as ((oldbaseline-(oldbaseline»gain))+reading).
 Scaling for deviationNot AvailableNoDeviation scalingYesIn mTouch, the deviation value is calculated as ((reading - baseline)»scaling).
 Number of samples taken for each measurementFilter levelYesOversampleYes 
 Sensor charging timeCharge share delay (CSD)YesPrecharge timeYesCSD 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 delayNot ApplicableNoAcquisition timeYesAcquisition 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 nodesNot AvailableNoAdditional sample capacitanceYesThis is used to improve the match between internal and external capacitance for a better sensing performance.
Sensor Configuration ParametersEnable auto-calibrationSensor charge time auto-tuneYesAuto-calibrationYesFor 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 toleranceEnable driven shieldYesDriven shieldYesBoth 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 non-scanning sensors as the shield, which improves water tolerance.
Sensor Touch ParametersNo. of additional touch measurements to confirm touchDetect integration (DI)YesDebounceYes 
 No. of additional touch measurements to confirm an out-of-touch detectionAway from touch detect integrationYesDebounceYes 
 Threshold for out-of-touch recalibrationAway from touch recalibration thresholdYesNegative thresholdNoNegative threshold is configurable in mTouch code and not in MCC.
 No. of additional touch measurements to confirm out-of-touch recalibrationNot AvailableNoConsecutive decodesYes 
 Rate of change of reference (baseline) for positive delta (deviation)Towards touch drift rateYesBaseline filtering: updateYesFor QTouch, value is scaled by 200 ms. In mTouch, a baseline update is done after this number of sensing cycles.
 Rate of change of reference (baseline) for negative delta (deviation)Away from touch drift rateYesBaseline filtering: updateYesCommon value for towards touch and away from touch in mTouch. For QTouch, the value is scaled by 200 ms.
 Amount of time the change of reference needs to be paused after removing the fingerDrift hold timeYesBaseline HoldNoValue is scaled by 200 ms for QTouch. This is configurable in the firmware for mTouch.
 Re-bursting modeRe-burst modeYesRe-burst modeYes 
 Enable sensor ON timeoutMax-ON duration (MOD)YesPress timeoutYesSet the value of MOD as zero in Atmel START to disable sensor ON timeout in QTouch.
 Sensor ON timeout unitNot AvailableNoPress timeout unitYesIn QTouch, unit is time in ms. In mTouch, the unit is main loop task calls by default.
 Set maximum sensor ON time/countsMax-ON duration (MOD)YesPress timeout countsYesIn QTouch, value is scaled by 200 ms.
Frequency Hop ParametersEnable multiple burst frequenciesEnable frequency hopYesEnable AFAYesFrequency hopping is enabled by default in mTouch.
 Enable auto changing of burst frequencyEnable frequency auto tuningYesAutomatic frequency adaptationYesIntelligently choose scan frequency at run-time to avoid noise frequency and its harmonics.
 Timer selection for frequency hopNot AvailableNoAFA filter timerYesThe PIC with ADCC doesn't need a timer to implement the frequency hopping.
 Number of frequencies used in touch measurementFrequency stepsYesMax/Min FrequencyNoThe mTouch will pick the frequencies in a range, which is configurable in the firmware.
 Threshold for noise frequency replacementMaximum varianceYesNoise ThresholdNoThis can be configured in the firmware for mTouch.
 Count for noise frequency replacementTune in countYesOver Limit ThresholdNoThis can be configured in the firmware for mTouch.
Clock Configuration SettingsOscillator selectionOscillatorsYesOscillator selectYesSelect the oscillator from the list.
 External clock selectionOscillatorsNoExternal clock selectYesSelect the external clock source from the list if an external oscillator is selected.
 Internal clock frequency selectionClock settings: prescalerYesHF internal clockYesSet the internal clock frequency by selecting the prescaler value.
 External clock frequency selectionFrequencyYesExternal clockYesEnter the external clock frequency if an external oscillator is selected.
 Clock source prescalerGeneric clock generator divisionYesClock dividerYesThe internal/external clock selected is divided by this prescaler.
 Enable low voltage programmingNot AvailableNoLow voltage programming enableYes 
 CPU and peripheral clock selectionClock sourceYesNot AvailableNoSelect the clock generator source for CPU and components from the list in QTouch.
 CPU clock dividerCPU clock prescalerYesNot AvailableNoThe CPU frequency will be the generic clock selected for the CPU divided by the prescaler.
 Enable watchdog timerNot AvailableNoWatchdog timer enableYes 

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