PSOC™ 4: MSCLP low-power multitouch mutual-capacitance touchpad

This code example demonstrates how to use CAPSENSE™ middleware to detect two finger touch positions on a mutual-capacitance-based touchpad widget in PSOC™ 4 devices with multi-sense converter low-power (MSCLP).

It also explains how to manually tune the mutual-capacitance-based touchpad for optimum performance according to parameters such as reliability, power consumption, response time, and linearity using the CSX-RM sensing technique and CAPSENSE™ Tuner GUI. Here, CAPSENSE™ crosspoint (CSX) represents the mutual-capacitance sensing technique and RM represents the ratiometric method.

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Requirements

• ModusToolbox™ v3.5 or later

• Board support package (BSP) minimum required version: 3.3.0

• Programming language: C

• Associated parts: PSOC™ 4100T PLUS

Supported toolchains (make variable 'TOOLCHAIN')

• GNU Arm® Embedded Compiler v11.3.1 (GCC_ARM) – Default value of TOOLCHAIN
• Arm® Compiler v6.22 (ARM)
• IAR C/C++ Compiler v9.50.2 (IAR)

Supported kits (make variable 'TARGET')

• PSOC™ 4100T PLUS CAPSENSE™ Prototyping kit (CY8CPROTO-041TP) – Default TARGET

Hardware setup

This example uses the board's default configuration. See the kit user guide to configure the required operating voltage on the kit and to setup the VDDA supply voltage refer to section Set up the VDDA supply voltage and debug mode in Device Configurator.

This application is tuned to perform optimally at the default voltage. However, you can observe the basic functionality at other supported voltages.

Table 1. Kit user guide and supporting voltages

Kit	User guide	1.8V	3.3V	5V
CY8CPROTO-041TP	PSOC™ 4100T Plus CAPSENSE™ Prototyping Kit guide	Yes	Yes	Yes*

Yes* - Kit default operating voltage

Software setup

See the ModusToolbox™ tools package installation guide for information about installing and configuring the tools package.

This example requires no additional software or tools.

Using the code example

Create the project

The ModusToolbox™ tools package provides the Project Creator as both a GUI tool and a command line tool.

Use Project Creator GUI

1. Open the Project Creator GUI tool.

   There are several ways to do this, including launching it from the dashboard or from inside the Eclipse IDE. For more details, see the Project Creator user guide (locally available at {ModusToolbox™ install directory}/tools_{version}/project-creator/docs/project-creator.pdf).

2. On the Choose Board Support Package (BSP) page, select a kit supported by this code example. See Supported kits.

   Note: To use this code example for a kit not listed here, you may need to update the source files. If the kit does not have the required resources, the application may not work.

3. On the Select Application page:

   a. Select the Applications(s) Root Path and the Target IDE.

   Note: Depending on how you open the Project Creator tool, these fields may be pre-selected for you.

   b. Select this code example from the list by enabling its check box.

   Note: You can narrow the list of displayed examples by typing in the filter box.

   c. (Optional) Change the suggested New Application Name and New BSP Name.

   d. Click Create to complete the application creation process.

Use Project Creator CLI

The 'project-creator-cli' tool can be used to create applications from a CLI terminal or from within batch files or shell scripts. This tool is available in the {ModusToolbox™ install directory}/tools_{version}/project-creator/ directory.

Use a CLI terminal to invoke the 'project-creator-cli' tool. On Windows, use the command-line 'modus-shell' program provided in the ModusToolbox™ installation instead of a standard Windows command-line application. This shell provides access to all ModusToolbox™ tools. You can access it by typing "modus-shell" in the search box in the Windows menu. In Linux and macOS, you can use any terminal application.

The following example clones the "CAPSENSE™ MSCLP mutual capacitance touchpad tuning" application with the desired name "MSCLPlowpowerMutualCapTouchpadTuning" configured for the CY8CPROTO-041TP BSP into the specified working directory, C:/mtb_projects:

project-creator-cli --board-id CY8CPROTO-041TP --app-id mtb-example-psoc4-msclp-mutual-capacitance-touchpad --user-app-name MSCLPMutualCapTouchpadTuning --target-dir "C:/mtb_projects"

The 'project-creator-cli' tool has the following arguments:

Argument	Description	Required/optional
--board-id	Defined in the field of the BSP manifest	Required
--app-id	Defined in the field of the CE manifest	Required
--target-dir	Specify the directory in which the application is to be created if you prefer not to use the default current working directory	Optional
--user-app-name	Specify the name of the application if you prefer to have a name other than the example's default name	Optional

Note: The project-creator-cli tool uses the git clone and make getlibs commands to fetch the repository and import the required libraries. For details, see the "Project creator tools" section of the ModusToolbox™ tools package user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mtb_user_guide.pdf).

Open the project

After the project has been created, you can open it in your preferred development environment.

Eclipse IDE

If you opened the Project Creator tool from the included Eclipse IDE, the project will open in Eclipse automatically.

For more details, see the Eclipse IDE for ModusToolbox™ user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mt_ide_user_guide.pdf).

Visual Studio (VS) Code

Launch VS Code manually, and then open the generated {project-name}.code-workspace file located in the project directory.

For more details, see the Visual Studio Code for ModusToolbox™ user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mt_vscode_user_guide.pdf).

Keil µVision

Double-click the generated {project-name}.cprj file to launch the Keil µVision IDE.

For more details, see the Keil µVision for ModusToolbox™ user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mt_uvision_user_guide.pdf).

IAR Embedded Workbench

Open IAR Embedded Workbench manually, and create a new project. Then select the generated {project-name}.ipcf file located in the project directory.

For more details, see the IAR Embedded Workbench for ModusToolbox™ user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mt_iar_user_guide.pdf).

Command line

If you prefer to use the CLI, open the appropriate terminal, and navigate to the project directory. On Windows, use the command-line 'modus-shell' program; on Linux and macOS, you can use any terminal application. From there, you can run various make commands.

For more details, see the ModusToolbox™ tools package user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mtb_user_guide.pdf).

Operation

1. Connect the board to your PC using a USB cable through the KitProg3 USB connector.

2. Program the board using one of the following:

   Using Eclipse IDE

   1. Select the application project in the Project Explorer.

   2. In the Quick Panel, scroll down, and click <Application Name> Program (KitProg3_MiniProg4).

   In other IDEs

   Follow the instructions in your preferred IDE.

   Using CLI

   From the terminal, execute the make program command to build and program the application using the default toolchain to the default target. The default toolchain is specified in the application's Makefile but you can override this value manually:

   make program TARGET=<BSP> TOOLCHAIN=<toolchain>
   

   Example:

   make program TARGET=CY8CPROTO-041TP TOOLCHAIN=GCC_ARM
   

3. After programming, the application starts automatically.

   Note: After programming, you may see the following error message if debug mode is disabled, see Table 13 for the default debug configuration in the supported kits. This can be ignored or enabling debug solves this error.

   "Error: Error connecting Dp: Cannot read IDR"

4. To test the application, slide your finger over the CAPSENSE™ touchpad and observe the LED behavior as mentioned in Table 2, Perform gestures on the touchpad and observe the corresponding LED responses listed in Table 3.

   Table 2. LED indications and status

   Scenario	CY8CPROTO-041TP	Status
   Touch (Column)	LED3	Brightness increases when the finger is swiped from left to right
   Touch (Row)	LED2	Brightness increases when the finger is swiped from bottom to top

   Table 3. LED indications for gestures

   Gesture Type	CY8CPROTO-041TP	Response
   One-finger single click	LED5	Turns ON for 500 ms
   One-finger double click	LED6	Turns ON for 500 ms
   One-finger flick in up direction	LED6	Blinks
   One-finger flick in down direction	LED5	Blinks
   One-finger flick in left direction	LED2	Blinks
   One-finger flick in right direction	LED3	Blinks
   Two-finger single click	LED5 and LED6	Both LEDs turn ON for 500 ms
   One-finger click & drag	LED6	Turns ON; LED2 and LED3 indicate the drag direction

   Note: One-finger click and drag gesture is triggered when the finger movement follows this sequence: Touchdown → Lift Off → Touchdown → Drag .

5. Do the following to monitor the CAPSENSE™ data using the CAPSENSE™ Tuner application:

   Monitor data using CAPSENSE™ Tuner

   1. Open CAPSENSE™ Tuner from the BSP Configurators section in the IDE Quick Panel.

      You can also run the CAPSENSE™ Tuner application in standalone mode from {ModusToolbox™ install directory}/ModusToolbox/tools_{version}/capsense-configurator/capsense-tuner. In this case, after opening the application, select File > Open and open the design.cycapsense file of the respective application, which is present in the {Application root directory}/bsps/TARGET_APP_<BSP-NAME>/config/ folder.

      See the ModusToolbox™ user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mtb_user_guide.pdf) for options to start CAPSENSE™ Tuner using the CLI.

   2. Ensure that the kit is in CMSIS-DAP bulk mode (KitProg3 status LED is ON and not blinking). To learn how to update the firmware and switch modes in KitProg3, see Firmware-loader.

   3. In the Tuner application, click on the Tuner Communication Setup icon or select Tools > Tuner Communication Setup. In the window, select the I2C checkbox under KitProg3 and configure as follows:

      • I2C address: 8
      • Sub-address: 2 bytes
      • Speed (kHz): 400

      These are the same values set in the EZI2C resource.

      Figure 2. Tuner Communication Setup parameters

      

   4. Click Connect or select Communication > Connect to establish a connection.

      Figure 3. Establish a connection

      

   5. Click Start or select Communication > Start to start data streaming from the device.

      Figure 4. Start tuner communication

      

      The Widget/Sensor parameters tab gets updated with the parameters configured in the CAPSENSE™ Configurator window. The tuner displays the data from the sensor in the Widget View and Graph View tabs.

6. Set the Read Mode to Synchronized. Under the Widget View tab, you can see the touchpad widget sensors highlighted when you touch it.

   Figure 5. Widget view of the CAPSENSE™ Tuner

   

7. You can view the raw count, baseline, and difference count for each sensor and also the touchpad position in the Graph View tab. For example, to view the sensor data for a single sensor in Touchpad, select Touchpad_Rx0_Tx0 under Touchpad.

   Figure 6. Graph view of the CAPSENSE™ Tuner

   

8. The Touchpad View tab shows the heat map view and the finger movement can be visualized on the same.

   Figure 7. Touchpad view of the CAPSENSE™ Tuner

   

9. Observe the Widget/Sensor parameters section in the CAPSENSE™ Tuner window. The compensation CDAC values for each touchpad sensor element calculated by the CAPSENSE™ resource is displayed as shown in Figure 7.

10. Verify that the signal to noise ratio (SNR) is greater than 5:1 by following the steps given in Stage 4 of the Tuning procedure section.

    The linearity of the position graph, non-reporting of false touches, and no discontinuity in the line drawing indicate a proper tuning.

11. The Gesture View tab visually represents evaluation and tuning of gestures (from one widget at a time). The Gesture View tab is disabled when there are no gesture widgets in the configuration.

    Figure 8. Gesture View of CAPSENSE™ Tuner

    

    Note: See the "Gesture in CAPSENSE™" section of PSOC™ 4 and PSOC™ 6 MCU CAPSENSE™ design guide for all gesture-related configuration parameters appear after enabling gestures.

12. Gesture Monitor provides visual indication for a detected gesture. Gesture Event History logs the detected gestures information.

    Note: To open the Gesture Monitor window, Select View > Gesture Monitor/Gesture Event History

    Figure 9. Gesture Monitor view of CAPSENSE™ Tuner

    

Note : See the code example PSOC™ 4: PSoC™ 4: MSCLP low-power CSD buttonto observe the power state transitions. Measure current at different power modes section. The code example also explains the scan time and process time measurements.

Tuning procedure

Create custom BSP for your board

1. Create a custom BSP for your board with any device by following the steps given in ModusToolbox™ BSP Assistant user guide.

2. Open the design.modus file from the {Application root directory}/bsps/TARGET_APP_<BSP-NAME>/config/ folder obtained in the previous step and enable CAPSENSE™ to get the design.cycapsense file. CAPSENSE™ configuration can then be started from scratch as explained below.

The following steps explain the tuning procedure.

Note: See the "Selecting CAPSENSE™ hardware parameters" section of PSOC™ 4 and PSOC™ 6 MCU CAPSENSE™ design guide to learn about the considerations for selecting each parameter values.

The tuning flow of the proximity widget is shown in Figure 10.

Figure 10. CSX touchpad widget tuning flow

Do the following to tune the touchpad widget:

Stage 1: Set initial hardware parameters

Stage 2: Set the sense clock frequency

Stage 3: Obtain crossover point and noise

Stage 4. Fine-tune sensitivity to improve SNR

Stage 5: Tune threshold parameters

Stage 1: Set initial hardware parameters

1. Connect the board to your PC using a USB cable through the KitProg3 USB connector.

2. Launch the Device Configurator tool.

   You can launch the Device Configurator in Eclipse IDE for ModusToolbox™ from the BSP Configurators section in the IDE Quick panel or in standalone mode from {ModusToolbox™ install directory}/ModusToolbox/tools_{version}/device-configurator/device-configurator. In this case, after opening the application, select File > Open and open the design.modus file of the respective application, which is present in the {Application root directory}/bsps/TARGET_APP_<BSP-NAME>/config/ folder.

3. In the PSOC™ 4100TP kit, the touchpad pins are connected to CAPSENSE™ channel (MSCLP 0). Therefore, make sure to enable CAPSENSE™ channel in the Device Configurator, as shown in Figure 11.

   Figure 11. Enable MSCLP channel in Device Configurator

   

   Save the changes and close the window.

4. Launch the CAPSENSE™ Configurator tool.

   You can launch the CAPSENSE™ Configurator tool in Eclipse IDE for ModusToolbox™ from the 'CAPSENSE™' peripheral setting in Device Configurator or directly from the BSP Configurators section in the IDE Quick panel. You can also launch it in standalone mode from {ModusToolbox™ install directory}/ModusToolbox/tools_{version}/capsense-configurator/capsense-configurator. In this case, after opening the application, select File > Open and open the design.cycapsense file of the respective application, which is present in the {Application root directory}/bsps/TARGET_APP_<BSP-NAME>/config/ folder.

   See the ModusToolbox™ CAPSENSE™ Configurator tool guide for step-by-step instructions on how to configure and launch CAPSENSE™ in ModusToolbox™.

5. In the Basic tab, note that a Touchpad is configured with CSX RM (Mutual-cap) Sensing mode.

   Figure 12. CAPSENSE™ Configurator - Basic tab

   

6. Go to Advanced > General tab and do the following:

   Table 4. Widget Details

   Parameter	Setting	Comment
   CAPSENSE™ IMO Clock frequency	46	Frequency of clock used as source for the CAPSENSE™ peripheral
   Modulator clock divider	1	Set to obtain the optimum modulator clock frequency
   Number of init sub-conversions	3	Set to ensure proper initialization of CAPSENSE™.

   Note: Retain the default settings for all regular and low-power widget filters. You can enable or update the filters later depending on the signal-to-noise ratio (SNR) requirements in Stage 3: Fine-tune for required SNR, power, and refresh rate.

   Filters are used to reduce the peak-to-peak noise; however, using filters will result in a higher scan time.

   Figure 13. CAPSENSE™ Configurator - General settings

   

   Note: Each tab has a Restore Defaults button to restore the parameters of that tab to their default values.

7. Go to the CSX Settings tab and make the following changes:

   Table 5. Scan Setting

   Parameter	CY8CPROTO-041TP	Comment
   Inactive sensor connection	Ground	Connects the inactive sensors (configured sensors which are not scanned in a given scan-slot) to the ground.
   Number of reported fingers	2	Set for two-finger detection.
   Raw count calibration level (%)	40	If the sensor raw count saturates (equals Max Raw count) on touch, reduce the Raw count calibration level (%), which helps avoid saturation.

   Figure 14. CAPSENSE™ Configurator - Advanced CSX settings

   

8. Go to the Widget Details tab. Select Touchpad from the left pane and set the following:

   Table 6. Initial widget parameter Setting

   Parameter	Setting	Comment
   Maximum X-Axis position	255	A touch on touchpad produces a position value from 0 to Maximum X-Axis position
   Maximum Y-Axis position	255	A touch on touchpad produces a position value from 0 to Maximum Y-Axis position
   Tx clock divider	Default	Value is set in Stage 2: Set sense clock frequency.
   Clock source	Direct	Direct clock is a constant frequency sense clock source. When you chose this option, the sensor pin switches with a constant frequency.
   Number of sub-conversions	25	Good starting point to ensure a fast scan time and sufficient signal. This value is adjusted as required in Stage 3: Fine-tune for required SNR, power, and refresh rate.
   Finger threshold	20	Initially set to a low value which allows the Touchpad View to track the finger movement during tuning.
   Noise threshold	10	Baseline is not updated when raw count is above baseline + noise threshold.
   Negative noise threshold	10	Baseline is not updated when raw count is below baseline - Negative noise threshold.
   Hysteresis	5	Prevents sensor status toggling due to system noise.
   ON debounce	10	Number of consecutive scans during which a sensor must be active so that a touch is reported.
   Enable gestures	True/False	Select the gestures you want to include in your application.

   These values reduce the influence of the baseline on the sensor signal, which helps get the true difference count. Retain the default values for the widget threshold parameters; these parameters are set in Stage 5.

   Figure 15. CAPSENSE™ Configurator - Widget details settings

   

9. Go to the Scan Configuration tab to select the pins, the scan slots, and do the following:

   • Configure the pin for the electrode using the drop-down menu.

   • Configure the scan slot using the Auto-Assign Slots option or or enter a slot number for each each sensor.

   • Check the notice list for warning or errors.

   Note: Enable the Notice List in the View menu if it is not visible.

   Figure 16. Scan Configuration tab

   

10. Click Save to apply the settings.

Stage 2: Set the sense clock frequency

The sense clock is derived from the modulator clock using a sense clock divider and is used to scan the sensor by driving the CAPSENSE™ switched capacitor circuits. Both the clock source and clock divider are configurable. The sense clock divider should be configured in a way that the pulse width of the sense clock is long enough to let the sensor capacitance charge and discharge completely. This is verified by observing the charging and discharging waveforms of the sensor using an oscilloscope and an active probe. The sensors should be probed close to the electrode and not at the sense pins or the series resistor.

See Figure 17 and Figure 18 for waveforms observed on the shield. Figure 17 shows proper charging when the sense clock frequency is correctly tuned. The pulse width is at least 5 Tau, i.e., the voltage reaches at least 99.3% of the required voltage at the end of each phase. Figure 18 shows incomplete settling (charging/discharging).

Figure 17. Proper charge cycle of a sensor

Figure 18. Improper charge cycle of a sensor

To set the proper sense clock frequency, follow these steps:

1. Program the board and launch CAPSENSE™ Tuner.

2. See the charging waveform of the sensor as described earlier.

3. If the charging is incomplete, increase the sense clock divider. This can be done in CAPSENSE™ Tuner by selecting the Sensor and editing the Sense Clock Divider parameter in the Widget/Sensor Parameters panel.

   Note: The sense clock divider should be divisible by 2. This ensures that both the scan phases have equal durations.

   After editing the value, click the Apply to Device button and observe the waveform again. Repeat this until you observe complete settling.

4. Click the Apply to Project button to save the configuration to your project.

   Figure 19. Sense Clock Divider setting

   

5. Repeat this process for all the sensors and the shield. Each sensor may require a different sense clock divider value to charge/discharge completely. But all the sensors that are in the same scan slot need to have the same sense clock source, sense clock divider, and number of sub-conversions. Therefore, take the largest sense clock divider in a given scan slot and apply it to all the other sensors that share that slot.

Table 7. Sense clock divider settings obtained for supported kits

Parameter	CY8CPROTO-041TP
Sense clock divider	16

Stage 3: Obtain crossover point and noise

1. Program the board.

2. Launch the CAPSENSE™ Tuner to monitor the CAPSENSE™ data and for CAPSENSE™ parameter tuning and SNR measurement.

   See the CAPSENSE™ Tuner guide for step-by-step instructions on how to launch and configure the CAPSENSE™ Tuner in ModusToolbox™ software.

3. Capture the raw counts of each sensor element in the touchpad (as shown in Figure 20) and verify that they are approximately (± 5%) equal to 40% of the MaxCount. See the design guide for the MaxCount equation.

   1. Go to the Touchpad View tab and change the Display settings as shown:

      Table 8. Display settings

      Parameter	Setting
      Display mode	Touch reporting
      Data type	RawCount
      Value type	Current
      Number of samples	1000

   Figure 20. Raw counts obtained on the Touchpad View tab of the Tuner window

   

4. Capture and note the peak-to-peak noise of each sensor element in the touchpad.

   1. From the Widget Explorer section, select the Touchpad widget.

   2. Go to the Touchpad View tab and change the Display settings as shown:

      Table 9. Display settings

      Parameter	Setting
      Display mode	Touch reporting
      Data type	RawCount
      Value type	Max-Min
      Number of samples	1000

      Capture the variation in the raw counts for 1000 samples, without placing a finger (which gives the peak-to-peak noise) and note the highest noise.

   Figure 21. Noise obtained on the Touchpad View tab of the Tuner window

   

   Table 10. Max peak-to-peak noise obtained in supported kits

   Kit	Max peak-to-peak noise
   CY8CPROTO-041TP	130

   
   

5. A finger (6 mm) should be held on the touchpad in the least touch intensity (LTI) position (at the intersection of four nodes) as shown in Figure 22.

   Figure 22. Least touch intensity (LTI) position

   

   Note: Finger movement during the test can artificially increase the noise level.

   1. Go to the Touchpad View tab and change the Display settings as follows:

      • Display mode: Touch Reporting

      • Data type: DiffCount

      • Value type: Current

   2. Place the finger in a way that you obtain an almost equal signal in all four intersecting nodes (look at the heat map displayed in the Touchpad View tab as shown in Figure 23).

      Note: The LTI signal is measured at the farthest point of the touchpad from the sensor pin connection, where the sensors have the worst-case RC-time constant.

   Figure 23. LTI position in Touchpad View

   

   as shown in Figure 23 LTI Signal = (470 + 514 + 495 + 559)/4 = 510

   Table 11. LTI signal obtained in supported kits

   Kit	LTI signal
   CY8CPROTO-041TP	850

Stage 4. Fine-tune sensitivity to improve SNR

The CAPSENSE™ system may be required to work reliably in adverse conditions, such as a noisy environment. The touchpad sensors should be tuned with SNR > 5:1 to avoid triggering false touches and to make sure that all intended touches are registered in these adverse conditions.

Note: For gesture detection, it is recommended to have approximately 10:1 SNR.

1. Ensure that the LTI Signal count is greater than 50 and meets at least 5:1 SNR (using Equation 1).

   In the CAPSENSE™ Tuner window, increase the Number of sub-conversions (located in the Widget/Sensor Parameters section, under Widget Hardware Parameters) by 10 until you achieve this requirement.

   Equation 1: Measuring the SNR

   

   Where,

   • LTI signal is the signal obtained as mentioned in Table 11 for supported kits.

   • Pk-Pk noise is the peak-to-peak noise obtained as shown in Table 10 for supported kits.

   SNR is measured using Equation 1.

   Here, from Table 11 and Table 10,

   SNR = 850/130 = 6.5

   Note: Ensure that the Number of sub-conversions (Nsub) does not exceed the max limit and saturate the raw count.

2. Update the number of sub-conversions

   • Update the number of sub-conversions directly in the Widget/Sensor parameters tab of the CAPSENSE™ Tuner.

   • PSOC™ 4 CAPSENSE™ devices with MSCLP have a built-in CIC2 filter. Enabling the CIC2 filter increases the resolution while maintaining the same scan time. see AN234231 - PSoC™ 4 CAPSENSE™ ultra-low-power capacitive sensing techniques for detailed information on CIC2 filter.

   • Current consumption is directly proportional to number of sub-conversions. Therefore, decrease the number of sub-conversions to achieve lower current consumption.

     Note: Number of sub-conversions should be greater than or equal to 8.

3. After changing the Number of sub-conversions, click Apply to Device to send the setting to the device. The change is reflected in the graphs.

Note: The Apply to Device option is enabled only when the Number of sub-conversions is changed.

4. If the SNR condition is not achieved even with the maximum number of sub-conversions, enable filters in the General settings (go to the Advanced tab of the CAPSENSE™ Configurator). This is generally not required for this kit.

Stage 5: Tune threshold parameters

After confirming that your design meets the timing parameters and power requirements and the SNR is greater than 5:1, set your threshold parameters.

Note: Thresholds are set based on the LTI position, because it is the least valid touch signal that can be obtained.

For measuring the Hysteresis, do the following:

1. Place the finger in the LTI position.

2. Set the Data type to DiffCount and Value type to Max-Min in the Touchpad View tab and click Clear.

3. Record the MAXIMUM of all four max-min count values (Max_Min_count) of the selected 2x2 sensors.

   Figure 24. Obtaining the hysteresis

   

4. Hysteresis = Max_Min_count/2 = 85/2 = 43

Set the recommended threshold values for the Touchpad widget using the LTI signal value obtained in Stage 4:

Table 12. Software tuning parameters obtained for supported kits

Parameter	CY8CPROTO-041TP	Remark
Number of sub-conversions	100	-
Finger threshold	680	80% of the lower LTI signal
Noise threshold	340	Twice the highest noise or 40% of the lower LTI signal (whichever is greater)
Negative noise threshold	340	Twice the highest noise or 40% of the lower LTI signal (whichever is greater)
Hysteresis	50	10% of the lower LTI signal
Low baseline reset	30	30 (by default)
ON debounce	3	Default
Velocity	2500	(Default) The 'Velocity' parameter is not required for single finger detection

Note: For multiple finger detection, if the velocity value is low, two touches at different positions are considered to be two different finger touches. On the other hand, if it is set at a higher value, it is considered to be the same finger moving to a different position.

Apply settings to firmware

1. Click Apply to Device and Apply to Project in the CAPSENSE™ Tuner window to apply the settings to the device and project, respectively.

2. Close the tuner.

   Figure 26. Apply to Project

   

Debugging

You can debug this project to step through the code. In the IDE, use the <Application Name> Debug (KitProg3_MiniProg4) configuration in the Quick Panel. For details, see the "Program and debug" section in the Eclipse IDE for ModusToolbox™ user guide.

To enable the debug option, see the Setup VDDA and Debug mode section. To achieve lower power consumption, it is recommended to disable it when not debugging.

see, Table 13 for the default debug configuration in the supported kits,

Table 13. Debug mode option status

Kit	Debug mode
CY8CPROTO-041TP	Enabled

Design and implementation

The project contains a touchpad widget configured in CSX-RM Sensing mode. See the Tuning procedure section for step-by-step instructions to configure the other settings of the CAPSENSE™ Configurator.

The project uses the CAPSENSE™ middleware (see ModusToolbox™ user guide for more details on selecting a middleware). See AN85951 – PSOC™ 4 and PSOC™ 6 MCU CAPSENSE™ design guide for more details on CAPSENSE™ features and usage.

The ModusToolbox™ provides a GUI-based Tuner application for debugging and tuning the CAPSENSE™ system. The CAPSENSE™ Tuner application works with EZI2C and UART communication interfaces. This project has an SCB block configured in EZI2C mode to establish communication with the onboard KitProg, which in turn enables reading the CAPSENSE™ raw data by the CAPSENSE™ Tuner (see Figure 29).

The CAPSENSE™ data structure that contains the CAPSENSE™ raw data is exposed to the CAPSENSE™ Tuner by setting up the I2C communication data buffer with the CAPSENSE™ data structure. This enables the tuner to access the CAPSENSE™ raw data for tuning and debugging CAPSENSE™.

The successful tuning of the touchpad is indicated by the user LED in the prototyping kit. The LED2 brightness increases when the finger is moved from bottom to top and LED3 brightness increases when the finger is moved from left to right on the touchpad.

Set up the VDDA supply voltage and debug mode in Device Configurator

1. Open Device Configurator from the Quick panel.

2. Go to the Systems tab, select the Power resource, and set the VDDA value under Operating Conditions as shown in Figure 28.

Figure 27. Setting the VDDA supply in the system tab of Device Configurator

3. By default, see Table 13 for the default debug configuration in the supported kits. Enable the debug mode to enable the SWD pins, as shown in Figure 28:

   Figure 28. Enable Debug mode in the System tab of Device Configurator

Resources and settings

See the Operation section for step-by-step instructions to configure CAPSENSE™ Configurator.

Figure 29. Device Configurator - EZI2C peripheral parameters

Figure 30. PWM settings

Table 14. Application resources

Resource	Alias/object	Purpose
SCB (I2C) (PDL)	CYBSP_EZI2C	EZI2C slave driver to communicate with CAPSENSE™ Tuner GUI
CAPSENSE™	CYBSP_MSCLP0	CAPSENSE™ driver to interact with the MSCLP hardware and interface the CAPSENSE™ sensors
Digital pin	CYBSP_USER_LED1, CYBSP_USER_LED2, CYBSP_USER_LED3, CYBSP_USER_LED4	To visualise the touchpad response and gestures
PWM	CYBSP_PWM	To drive the user LED which visualizes touchpad response

Firmware flow

Figure 31. Firmware flowchart

Related resources

Resources	Links
Application notes	AN79953 – Getting started with PSOC™ 4 AN85951 – PSOC™ 4 and PSOC™ 6 MCU CAPSENSE™ design guide AN234231 - PSoC™ 4 CAPSENSE™ ultra-low-power capacitive sensing techniques
Code examples	Using ModusToolbox™ on GitHub Using PSOC™ Creator
Device documentation	PSOC™ 4 datasheets PSOC™ 4 technical reference manuals
Development kits	Select your kits from the Evaluation board finder.
Libraries on GitHub	mtb-pdl-cat2 – PSOC™ 4 Peripheral Driver Library (PDL)
Middleware on GitHub	capsense – CAPSENSE™ library and documents
Tools	ModusToolbox™ – ModusToolbox™ software is a collection of easy-to-use libraries and tools enabling rapid development with Infineon MCUs for applications ranging from wireless and cloud-connected systems, edge AI/ML, embedded sense and control, to wired USB connectivity using PSOC™ Industrial/IoT MCUs, AIROC™ Wi-Fi and Bluetooth® connectivity devices, XMC™ Industrial MCUs, and EZ-USB™/EZ-PD™ wired connectivity controllers. ModusToolbox™ incorporates a comprehensive set of BSPs, HAL, libraries, configuration tools, and provides support for industry-standard IDEs to fast-track your embedded application development. PSOC™ Creator – IDE for PSOC™ and FM0+ MCU development

Other resources

Infineon provides a wealth of data at www.infineon.com to help you select the right device, and quickly and effectively integrate it into your design.

The Bluetooth® word mark and logos are registered trademarks owned by Bluetooth SIG, Inc., and any use of such marks by Infineon is under license.

Document history

Document title: CE240431 – PSOC™ 4: MSCLP low power CSX touchpad

Version	Description of change
1.0.0	New code example This version is not backward compatible with ModusToolbox™ v3.1
2.0.0	Major update to support ModusToolbox™ v3.3. This version is not backward compatible with previous versions of ModusToolbox™
3.0.0	Major update to support ModusToolbox™ v3.5. This version is not backward compatible with previous versions of ModusToolbox™

All referenced product or service names and trademarks are the property of their respective owners.

The Bluetooth® word mark and logos are registered trademarks owned by Bluetooth SIG, Inc., and any use of such marks by Infineon is under license.

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