PSoC™ 4: MSCLP self-capacitance touchpad tuning

This code example demonstrates how to use the CAPSENSE™ middleware to detect a finger touch position on a self-capacitance-based touchpad widget in PSoC™ 4000T device with multi-sense converter low-power (MSCLP).

In addition, this code example also explains how to manually tune the self-capacitance-based touchpad for optimum performance according to parameters such as reliability, power consumption, response time, and linearity using the CSD-RM sensing technique and CAPSENSE™ Tuner. Here, capacitive sigma-delta (CSD) represents the self-capacitance sensing technique and RM represents the ratiometric method.

View this README on GitHub.

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Requirements

ModusToolbox™ v3.2 or later

Note: This code example version requires ModusToolbox™ version 3.2 or later, and is not backward compatible with v3.1 or older versions.
Board support package (BSP) minimum required version: 3.2.0
Programming language: C
Associated parts: PSoC™ 4000T

Supported toolchains (make variable 'TOOLCHAIN')

GNU Arm® Embedded Compiler v11.3.1 (GCC_ARM) – Default value of TOOLCHAIN
Arm® Compiler v6.16 (ARM)
IAR C/C++ Compiler v9.30.1 (IAR)

Supported kits (make variable 'TARGET')

PSoC™ 4000T CAPSENSE™ Evaluation Kit (CY8CKIT-040T) – Default value of TARGET

Hardware setup

This example uses the board's default configuration. See the kit user guide to ensure that the board is configured correctly to use VDDA at 1.8 V.

Note: The PSoC™ 4 kits (except CY8CKIT-040T and CY8CKIT-041S-MAX) ship with KitProg2 installed. ModusToolbox™ requires KitProg3. Before using this code example, make sure that the board is upgraded to KitProg3. The tool and instructions are available in the Firmware Loader GitHub repository. If you do not upgrade, you will see an error like "unable to find CMSIS-DAP device" or "KitProg firmware is out of date".

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

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).
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.
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 "mtb-example-psoc4-msclp-self-capacitance-touchpad" application with the desired name "MSCLPSelfCapTouchpadTuning" configured for the CY8CKIT-040T BSP into the specified working directory, C:/mtb_projects:

project-creator-cli --board-id CY8CKIT-040T --app-id mtb-example-psoc4-msclp-self-capacitance-touchpad --user-app-name MSCLPSelfCapTouchpadTuning --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

Connect the board to your PC using the provided Micro-B USB cable through the KitProg3 USB connector as shown in Figure 1.

Figure 1. Connecting the CY8CKIT-040T kit with the PC
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 TOOLCHAIN=<toolchain>
```
Example:
```
make program TOOLCHAIN=GCC_ARM
```
After programming, the application starts automatically.

Note: After programming, you see the following error message if debug mode is disabled. This can be ignored or enabling the debug mode will solve this error.
```
"Error: Error connecting Dp: Cannot read IDR"
```
To test the application, slide your finger over the CAPSENSE™ touchpad and notice that LED1 and LED3 turn ON with green color when touched, and turn OFF when the finger is lifted.
- LED1 brightness increases when the finger is swiped from left to right.
- LED3 brightness increases when the finger is swiped from bottom to top.
You can also monitor the CAPSENSE™ data using the CAPSENSE™ Tuner application as follows:

Monitor data using CAPSENSE™ Tuner
1. Open CAPSENSE™ Tuner from the tools 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 open the CAPSENSE™ Tuner application using the CLI.
1. Ensure the kit is in CMSIS-DAP bulk mode (KitProg3 status LED is ON and not blinking). See Firmware-loader to learn how to update the firmware and switch modes in KitProg3.
2. In the tuner application, click on the Tuner Communication Setup icon or select Tools > Tuner Communication Setup. In the window, select I2C 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
Click Connect or select Communication > Connect to establish a connection.

Figure 3. Establish a connection
Click Start or select Communication > Start to start data streaming from the device.

Figure 4. Start tuner communication

The tuner displays the data from the sensor in the Widget View, Graph View, and Touchpad View tabs.
Set the Read mode to Synchronized mode. Navigate to the Widget View tab and observe that the TOUCHPAD_SELF_CAP widget is highlighted in blue color when you touch it.

Figure 5. Widget view of the CAPSENSE™ Tuner
You can view the raw count, baseline, difference count, status for each sensor, and touchpad position in the Graph View tab. For example, to view the sensor data for TOUCHPAD_SELF_CAP, select TOUCHPAD_SELF_CAP_Col0 under TOUCHPAD_SELF_CAP.

Figure 6. Graph View tab of the CAPSENSE™ Tuner
The Touchpad View tab shows the heatmap view and the finger movement can be visualized on the same.

Figure 7. Touchpad view of the CAPSENSE™ Tuner
See the Widget/Sensor Parameters section in the CAPSENSE™ Tuner window. The configuration parameters for each touchpad sensor element calculated by the CAPSENSE™ resource are displayed as shown in Figure 7.
Verify that the signal-to-noise ratio (SNR) is greater than 5:1 and the signal count is above 50 by following the steps given in Stage 3: Obtain noise and crossover point.

Non-reporting of false touches and the linearity of the position graph indicate proper tuning.

Operation at other voltages

CY8CKIT-040T kit supports operating voltages of 1.8 V, 3.3 V, and 5 V. Use voltage selection switch available on top of the kit to set the preferred operating voltage and see the Set up the VDDA supply voltage and debug mode in Device Configurator section.

This application functionalities are optimally tuned for 1.8 V. However, you can observe the basic functionalities working across other voltages.

It is recommended to tune the application with the preferred voltages for better performance.

Tuning procedure

Create custom BSP for your board

Create a custom BSP for your board with any device by following the steps given in ModusToolbox™ BSP Assistant user guide. This code example is created for the CY8C4046LQI-T452 device.
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 be started from scratch as follows:

The following steps explain the tuning procedure.

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

Figure 8. CSD touchpad widget tuning flow

Do the following to tune the touchpad widget:

Stage 1: Set the initial hardware parameters
Stage 2: Set the sense clock frequency
Stage 3: Obtain noise and crossover point
Stage 4: Fine-tune sensitivity to improve SNR
Stage 5: Tune threshold parameters

Stage 1: Set the initial hardware parameters

Connect the board to your PC using the provided USB cable through the KitProg3 USB connector.
Launch the Device Configurator tool.

You can launch the Device Configurator in Eclipse IDE for ModusToolbox™ from the Tools 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 located in the {Application root directory}/bsps/TARGET_APP_<BSP-NAME>/config/ folder.
In the PSoC™ 4000T kit, the touchpad pins are connected to CAPSENSE™ channel (MSCLP 0). Therefore, ensure that you enable CAPSENSE™ channel in the Device Configurator as shown in Figure 9.

Figure 9. Enable MSCLP channel in the Device Configurator

Save the changes and close the window.
Launch the CAPSENSE™ Configurator tool.

You can launch the CAPSENSE™ Configurator tool in the Eclipse IDE from the CAPSENSE™ Peripherals tab in the Device Configurator or directly from the Tools 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 located 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™.
In the Basic tab, note that a single touchpad, TOUCHPAD_SELF_CAP is configured with CSD RM (self-cap) Sensing Mode.

Figure 10. CAPSENSE™ Configurator - Basic tab
Go to Advanced > General tab and do the following:
1. Select CAPSENSE™ IMO Clock frequency as 46 MHz.
2. Set the Modulator clock divider to 1 to obtain the maximum available modulator clock frequency as recommended in the PSoC™ 4 and PSoC™ 6 MCU CAPSENSE™ design guide.
  
  Note: The modulator clock frequency can be set to 46,000 kHz after changing the CAPSENSE™ IMO clock frequency to 46 MHz because the modulator clock is derived from the CAPSENSE™ IMO clock. In the CAPSENSE™ IMO clock frequency drop-down, select 46 MHz.
3. Set the Number of init sub-conversions based on the hint shown when you hover over the edit box. Retain the default value.
4. It is recommended to Enable IIR filter (first order) and set the IIR filter raw count coefficient: to 128 when the CIC2 filter is enabled. You can enable the filters later depending on the SNR requirements in Stage 4: Fine-tune sensitivity to improve SNR.
  
  Filters are used to reduce the peak-to-peak noise; however, using filters will result in a longer scan time.
Figure 11. CAPSENSE™ Configurator – General settings

Note: Each tab has a Restore Defaults button to restore the parameters of that tab to their default values.
Go to CSD Settings tab and make the following changes:
- Set Inactive sensor connection as Shield.
  
  Inactive sensors connected to shield provide better performance in terms of SNR and refresh rate (as the use of shield results in a reduction of sensor capacitance C_p and can be used if your design requires liquid tolerance).
- Set Shield mode to Active.
  
  MSCLP provides active and passive shielding. Active shielding is preferred for high-performance applications. Before enabling this option, ensure that your design has shield electrodes.
- Set Total shield count as 3.
  
  To improve noise immunity, configure all unused sensor pins as shield.
Raw count calibration level(%) helps in achieving the required CDAC calibration levels (85% of maximum count by default) for all sensors in the widget, while maintaining the same sensitivity across the sensor elements. This can be reduced, if application reaches the saturation level on a touch event.

Figure 12. CAPSENSE™ Configurator – Advanced CSD settings
Go to the Widget Details tab. Select TOUCHPAD_SELF_CAP from the left pane and then set the following:
1. Maximum X-Axis position and Maximum Y-Axis position: 255
2. Column sense clock divider: Default value (will be set in Stage 2: Set the sense clock frequency)
3. Row sense clock divider: Retain the default value (will be set in Stage 2: Set the sense clock frequency)
4. Clock source: Direct
  
  Note: Spread spectrum clock (SSC) or PRS clock can be used as a clock source to deal with EMI/EMC issues.
5. Number of sub-conversions: 12
  
  The value '12' is an appropriate starting point to ensure a fast scan time and sufficient signal. This value will be adjusted as required in Stage 4: Fine-tune sensitivity to improve SNR.
6. Finger threshold: 20
  
  Finger threshold is initially set to a low value which allows the Touchpad View to track the finger movement during tuning.
7. Noise threshold: 10
8. Negative noise threshold: 10
9. Hysteresis: 5
These values reduce the influence of the baseline on the sensor signal which helps to get the true difference count. Retain the default values for all other threshold parameters; these parameters are set in Stage 5: Tune threshold parameters.

Figure 13. CAPSENSE™ Configurator - Widget Details settings
To select pins and scan slots, go to Scan Configuration tab and do the following:

Figure 14. Scan Configuration tab
1. Configure pins for the electrodes using the drop-down menu.
2. Configure the scan slots using Auto-Assign Slots option.
  
  The summary section in the Scan Configuration tab shows nine scan slots (for nine sensors). Each sensor is allotted a scan slot based on the slot number.
3. Check the notice list for warnings or errors.
  
  Note: Enable the Notice List from the View menu if the notice list is not visible.
Click Save to apply the settings.

Stage 2: Set the sense clock frequency

The sense clock is derived from the modulator clock using a 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 such that the pulse width of the sense clock is long enough to allow the sensor capacitance to 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 15 and Figure 16 for waveforms observed on the shield. Figure 15 shows proper charging when the sense clock frequency is correctly tuned. The pulse width is at least 5 Tau, i.e., the voltage is reaching at least 99.3% of the required voltage at the end of each phase. Figure 16 shows incomplete settling (charging/discharging).

Figure 15. Proper charge cycle of a sensor

Figure 16. Improper charge cycle of a sensor

Program the board and launch CAPSENSE™ Tuner.
See the charging waveform of the sensor as described earlier.
If the charging is incomplete, increase the sense clock divider. Do this 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 4. This ensures that all four scan phases have equal durations.

After editing the value, click the Apply to Device button and observe the waveform again. Repeat this until complete settling is observed.
Click the Apply to Project button so that the configuration is saved to your project.

Figure 17. Sense clock divider setting
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.

Stage 3: Obtain noise and crossover point

To obtain the noise and crossover point, do the following:

Program the board.
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™.
Capture the raw counts of each sensor element in the touchpad as shown in Figure 18 and verify that they are approximately equal to 85% (± 5%) of the MaxCount. See AN234231 - Achieving lowest-power capacitive sensing with PSoC™ 4000T for the MaxCount equation.
1. Go to the Touchpad View tab and change the Display settings as follows:
  - Display mode: Touch reporting
  - Data type: RawCount
  - Value type: Current
  - Number of samples: 1000
Figure 18. Raw counts obtained on the Touchpad View tab in the Tuner window
Observe and note the peak-to-peak noise of each sensor element in the touchpad.
1. From the Widget Explorer section, select the widget TOUCHPAD_SELF_CAP.
2. Go to the Touchpad View tab and change the Display settings as follows:
  - Display mode: Touch reporting
  - Data type: RawCount
  - Value type: Max-Min
  - Number of samples: 1000
Figure 19. Noise obtained on the Touchpad View tab in the Tuner window

See the row and column having the highest raw counts without placing a finger (which gives the peak-to-peak noise) in the Touchpad View.
1. Capture the accurate noise by following these steps:
  
  a) Click on the highest value observed in the heatmap for Row.
  
  b) Click on SNR Measurement tab.
  
  c) Click on Acquire Noise.
  
  d) Repeat the above steps for the column as well.
Figure 20. Row noise obtained on the SNR Measurement tab in Tuner window

Figure 21. Column noise obtained on the SNR Measurement tab in Tuner window

Table 1. Maximum peak-to-peak noise obtained in CY8CKIT-040T kit

Kit Maximum peak-to-peak noise for row sensors Maximum peak-to-peak noise for column sensors

CY8CKIT-040T 212 125
Observe the sensor signal in the Graph View tab in the Sensor Signal graph display.

a) Select the columns in Widget Explorer as shown in Figure 22.

b) Firmly swipe the finger (6 mm) horizontally on the touchpad in the least touch intensity (LTI) position.

c) Note the lowest crossover point observed under Sensor Signal.

d) Repeat the above steps for row by swiping the finger vertically on the touchpad in the LTI position.

Note: The LTI signal is measured at the farthest point (not at the last column/row) of the touchpad from the sensor pin connection, where the sensors have the worst case RC-time constant.

Figure 22. Column signal obtained on the Graph View tab in Tuner window

Figure 23. Row signal obtained on the Graph View tab in Tuner window

Table 2. Sensor signal obtained in CY8CKIT-040T kit

Kit LTI signal for row sensors LTI signal for column sensors

CY8CKIT-040T 1329 1330

Kit	Maximum peak-to-peak noise for row sensors	Maximum peak-to-peak noise for column sensors
CY8CKIT-040T	212	125

Kit	LTI signal for row sensors	LTI signal for column sensors
CY8CKIT-040T	1329	1330

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 need to be tuned with SNR greater than 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 around 10:1 SNR.

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

In CAPSENSE™ Tuner window, increase the Number of sub-conversions (located in Widget Hardware Parameters > Widget/Sensor Parameters section) by 10 until you achieve at least 5:1 SNR.

Equation 1. SNR

Where,
- LTI signal is the signal obtained as shown in Figure 22 and Figure 23
- Pk-Pk noise is the peak-to-peak noise obtained as shown in Figure 20 and Figure 21
SNR is measured for row sensors and column sensors separately, using Equation 1.

From the values derived from figures mentioned earlier, an example SNR calculation can be calculated as:

SNR of column sensors = 1330/125 = 10.64; SNR of row sensors = 1329/212 = 6.26.
Update the number of sub-conversions.
1. Update the Number of sub-conversions (Nsub) directly in the Widget/Sensor parameters tab of the CAPSENSE™ Tuner.
2. CY8CKIT-040T kit has an in-built CIC2 filter which increases the resolution for the same scan time. See AN234231 - Achieving lowest-power capacitive sensing with PSoC™ 4000T for detailed information on the CIC2 filter.
3. Current consumption is directly proportional to the number of sub-conversions; therefore, decrease the number of sub-conversions to achieve lower current consumption.
  
  Note: The number of sub-conversions should be greater than or equal to 8, and they should not be increased beyond a certain limit such that the raw count does not increase more than 2¹⁶ (as it is a 16-bit counter).
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.

Note: Decrease the IIR filter coefficient if 5:1 SNR is not being achieved even with maximum Nsub.

Stage 5: Tune threshold parameters

After confirming that your design meets the timing parameters 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.

Set the recommended threshold values for the touchpad widget using the LTI signal value obtained in Stage 4: Fine-tune sensitivity to improve SNR.

Finger threshold – 80% of the lower LTI signal (either Row or Column)
Noise threshold – Twice the highest noise or 40% of the lower LTI signal (whichever is greater)
Negative noise threshold – Twice the highest noise or 40% of the lower LTI signal (whichever is greater)
Hysteresis – 10% of the lower LTI signal
ON debounce – '10' (set to '1' for gesture detection)
Low baseline reset – Default value of '30'
Velocity – Default value of '2500'

Note: The 'Velocity' parameter is not required for single finger detection.

Table 3. Software tuning parameters obtained for CY8CKIT-040T kit

Parameter	CY8CKIT-040T kit
Number of sub-conversions	46
Decimation rate	255
Finger threshold	1064
Noise threshold	532
Negative noise threshold	532
Hysteresis	133
ON debounce	10
Low baseline reset	30

Apply the settings to the firmware

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

Figure 24. Apply to project

The change is updated in the design.cycapsense file and reflected in the CAPSENSE™ Configurator.

Debugging

You can debug the example to step through the code.

In Eclipse 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.

In other IDEs

Follow the instructions in your preferred IDE.

By default, the debug option is disabled in the Device Configurator. To enable the debug option, see the Set up VDDA supply and debug mode in Device Configurator section. To achieve low-power consumption, it is recommended to disable it.

Design and implementation

The project contains a touchpad widget configured in CSD-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.

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 27.

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 RGB LED in the Evaluation Kit; the LED1 brightness increases when the finger is swiped from left to right, and the LED3 brightness increases when the finger is swiped from bottom to top on the touchpad.

The master output slave input (MOSI) pin of the SPI slave peripheral is used to transfer data to the three serially connected LEDs for controlling color, brightness, and ON or OFF operations. The three LEDs form a daisy-chain connection and communication happens over the serial interface to create an RGB configuration. The LED accepts a 8-bit input code, with three bytes for red, green, and blue color, five bits for global brightness, and three blank '1' bits. See the LED datasheet for more details.

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

Open Device Configurator from the Quick Panel.
Go to the System tab. Select the Power resource and set the VDDA value under Operating Conditions as shown in Figure 25.

Figure 25. Setting the VDDA supply in the System tab of Device Configurator
By default, the debug mode is disabled for this application to reduce power consumption. Enable the debug mode to enable the SWD pins as shown in Figure 26.

Figure 26. Enable debug mode in the System tab of Device Configurator

Resources and settings

Figure 27. EZI2C settings

Figure 28. SPI settings

Table 4. Application resources

Resource	Alias/object	Purpose
SCB (EZI2C) (PDL)	CYBSP_EZI2C	EZI2C slave driver to communicate with CAPSENSE™ Tuner
CAPSENSE™	CYBSP_MSC	CAPSENSE™ driver to interact with the MSCLP hardware and interface the CAPSENSE™ sensors
Digital pin	CYBSP_SERIAL_LED	To show the touchpad operation
SCB (SPI) (PDL)	CYBSP_MASTER_SPI	SPI master driver to drive the serial LED which visualizes touchpad response

Firmware flow

Figure 29. 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 – Achieving lowest-power capacitive sensing with PSoC™ 4000T
Code examples	Using ModusToolbox™ on GitHub
Device documentation	PSoC™ 4 datasheets PSoC™ 4 technical reference manuals
Development kits	Select your kits from the Evaluation board finder.
Libraries on GitHub	mtb-hal-cat2 – Hardware Abstraction Layer (HAL) library
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.

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.

Document history

Document title: CE235338 - PSoC™ 4: MSCLP self-capacitance touchpad tuning

Version	Description of change
1.0.0	New code example This version is not backward compatible with ModusToolbox™ v2.4
1.1.0	Minor folder structure changes that does not break backward compatibility
2.0.0	Major update to support ModusToolbox™ v3.1 This version is not backward compatible with ModusToolbox™ v3.0
2.0.1	Minor configuration and readme update
3.0.0	Major update to support ModusToolbox™ v3.2 and CAPSENSE™ Middleware v5.0 This version is not backward compatible with ModusToolbox™ v3.1

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mtb-example-psoc4-msclp-self-capacitance-touchpad/README.md