PSoC™ 4: MSCLP low-power mutual-capacitance slider

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

In addition, this code example also explains how to manually tune the mutual-capacitance-based slider for optimum performance with respect to parameters such as reliability, power consumption, and response time using the CSX-RM sensing technique and CAPSENSE™ Tuner GUI. Here, CSX represents the mutual-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 v3.2 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™ Prototyping Kit (CY8CPROTO-040T) - Default 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 5 V.

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 "MSCLP low power CSX slider " application with the desired name "MSCLPMutualCapSlider" configured for the CY8CPROTO-040T BSP into the specified working directory, C:/mtb_projects:

project-creator-cli --board-id CY8CPROTO-040T --app-id mtb-example-psoc4-msclp-low-power-csx-slider --user-app-name MSCLPMutualCapSlider --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 USB cable through the KitProg3 USB connector as follows:

Figure 1. Connecting the CY8CPROTO-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. Ignore the error or enable the debug mode to solve this error.
```
"Error: Error connecting Dp: Cannot read IDR"
```
To test the application, slide your finger over the CAPSENSE™ slider and notice that the LED3 turns ON when touched and turns OFF when the finger is lifted. The LED3 brightness increases when the finger is swiped from left to right.
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 standalone 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.
2. Ensure that 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.
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 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 mode. Navigate to the Widget View tab, and you can see the LinerSlider0 widget highlighted in blue when you touch it.
  
  Figure 5. Widget View of the CAPSENSE™ Tuner
7. You can view the raw count, baseline, difference count, and status for each sensor in the Graph View tab. For example, to view the sensor data for LinerSlider0, select LinerSlider0_Rx0 under LinerSlider0.
  
  Figure 6. Graph View for the CAPSENSE™ Tuner
8. Observe the Widget/Sensor parameters section in the CAPSENSE™ Tuner window as shown in Figure 5.
9. Verify that the SNR is greater than 5:1 by following the steps given in Stage 4: Fine-tune sensitivity to improve SNR
Note: Non-reporting of false touches and the linearity of the position graph indicate proper tuning.

Operation at other voltages

CY8CPROTO-040T supports operating voltages of 1.8 V, 3.3 V, and 5 V. Refer to the kit user guide to set the preferred operating voltage and refer to section setup the VDDA supply voltage and Debug mode.

This application functionalities are optimally tuned for 5 V. However, basic functionalities works on other voltages.

For better performance, it is recommended to tune the application for the preferred voltages.

Measure current at different power modes

See the code example CE238817 that describes the steps of current measurement at different power modes.

Table 1. Measured current for different modes

Power mode	Refresh rate (Hz)	Current consumption (µA)
Active	128	114
Active low-refresh rate (ALR)	32	30
Wake-on-touch (WoT)	16	3.1

Note : The above WoT current was measured on a kit having Deep Sleep current of 1.7 µA. If the kit has a Deep Sleep current of 2.5 µA (typical), the WoT current is expected to be ~4.4 µA.

Tuning procedure

Create a custom BSP for your board

Create a custom BSP for your board having any device, by following the steps given in ModusToolbox™ BSP Assistant user guide. This code example was created for the device "CY8C4046LQI-T452".
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 section "Selecting CAPSENSE™ hardware parameters" in the PSoC™ 4 and PSoC™ 6 MCU CAPSENSE™ design guides to learn about the considerations for selecting each parameter value.

Figure 7. CSX slider widget tuning flow

Do the following to tune the slider widget:

Stage 1: Set the 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 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, which is present in the {Application root directory}/bsps/TARGET_APP_<BSP-NAME>/config/ folder.
In the PSoC™ 4000T Prototyping kit, the slider pin is connected to CAPSENSE™ channel (MSCLP 0). Therefore, make sure to enable CAPSENSE™ channel in the device configurator as shown in Figure 8.

Figure 8. Enable MSCLP channels in Device Configurator

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

You can launch the CAPSENSE™ Configurator tool in Eclipse IDE for ModusToolbox™ from the 'CAPSENSE™' peripheral setting 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, 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™.
In the Basic tab, note that the slider widget 'LinerSlider0' is configured as a CSX-RM (mutual-cap).

Figure 9. 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.
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. Use Wake-on-Touch settings to set the refresh rate and frame timeout while in the lowest power mode (Wake-on-Touch mode). Set Wake-on-Touch scan interval (µs) based on the required low-power state scan refresh rate. For example, to get a 16-Hz refresh rate, set the value to 62500.
5. Set the Number of frames in Wake-on-Touch as the maximum number of frames to be scanned in WoT mode, if there is no touch detected. This determines the maximum time the device will be kept in the lowest-power mode if there is no user activity. Calculate the maximum time by multiplying this parameter with the Wake-on-Touch scan interval (µs) value.
  
  For example, to get 10 seconds as the maximum time in WoT mode, set the Number of frames in Wake-on-Touch to 160 for the scan interval set as 62500 µs.
  
  Note: For tuning low-power widgets, the Number of frames in Wake-on-Touch must be less than the Maximum number of raw counts in SRAM based on the number of sensors in WoT mode as follows:
  
  Table 2. Maximum number of raw counts in SRAM
  
  Number of low
  power widgets Maximum number of
  raw counts in SRAM
  
  1 245
  
  2 117
  
  3 74
  
  4 53
  
  5 40
  
  6 31
  
  7 25
  
  8 21
  
  Figure 10. CAPSENSE™ Configurator – General settings
6. Retain the default settings for all regular and low-power widget filters. You can enable or update the filters later depending on the SNR requirements in Stage 3: Obtain crossover point and noise.
  
  Filters reduce the peak-to-peak noise, and using software filters results in a higher scan time.
Note: Each tab has a Restore Defaults button to restore the parameters of that tab to their default values.
Go to the CSD and CSX settings tab and make the following changes:

Table 3. CSD and CSX Parameters

Parameters CSD CSX

Inactive sensor connection Shield Ground

Shield mode Active NA

Total shield count 5 NA

Raw count calibration level(%) 70 40

Note: 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 11. CAPSENSE™ Configurator - Advanced CSD settings

Figure 12. CAPSENSE™ Configurator - Advanced CSX settings
Go to the Widget Details tab. Select LinerSlider0 from the left pane, and then set the following:
- Sense clock divider: Retain default value (will be set in Stage 2)
- Clock source: Direct
  
  Note: Spread spectrum clock (SSC) or PRS clock can be used as a clock source to deal with EMI/EMC issues.
- Number of sub-conversions: 60
  
  '60' is a good starting point to ensure a fast scan time and sufficient signal. This value is adjusted as required in Stage 5.
- Finger threshold: 20
- Noise threshold: 10
- Negative noise threshold: 10
- Low-baseline reset: 30
- Hysteresis: 5
- ON debounce: 3
  
  These values reduces the influence of baseline on the sensor signal, which helps to get the true difference-count. Retain the default values for the widget threshold parameters; these parameters are set in Stage 4.
Figure 13. CAPSENSE™ Configurator - Widget details tab under the Advanced tab
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 each sensor is allotted a scan slot based on the entered slot number
- Check the notice list for warning or error
Note: Enable the Notice List in the View menu if it is not visible.

Figure 14. Scan Configuration tab
Click Save to apply the settings.

Number of low power widgets	Maximum number of raw counts in SRAM
1	245
2	117
3	74
4	53
5	40
6	31
7	25
8	21

Parameters	CSD	CSX
Inactive sensor connection	Shield	Ground
Shield mode	Active	NA
Total shield count	5	NA
Raw count calibration level(%)	70	40

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 sense clock frequency is correctly tuned. The pulse width is atleast 5Tau i.e., the voltage is reaching atleast 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

** To set the sense clock frequency, follow the steps below:

Program the board and launch CAPSENSE™ Tuner.
Observe 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 2. This ensures that two 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 to save the configuration 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 should 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 the slot.

Stage 3: Obtain crossover point and noise

Program the board.
Launch the CAPSENSE™ Tuner to monitor the CAPSENSE™ data, tuning CAPSENSE™ parameter, 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 and note the peak-to-peak noise of each segment of the slider.

i. From the Widget Explorer section, select a sensor (for example, "LinearSlider0_Sns0").

ii. Go to the SNR Measurement tab and click Acquire Noise to capture peak-to-peak noise as shown in Figure 18.

Figure 18. Noise obtained on the SNR Measurement tab in Tuner window

iii. Repeat steps (i) and (ii) for all the sensors to capture peak-to-peak noise.

Table 4. Peak-to-peak noise obtained for each segment

Slider segment Peak-to-peak noise (CY8CPROTO-040T)

SNS0 21

SNS1 24

SNS2 25

SNS3 25

SNS4 27
Use a grounded metal finger (typically 6 mm ) and swipe it slowly at a constant speed from the start to the end of the slider.

i. Go to the Graph View tab to view a graph similar to Figure 20.

ii. Get the upper crossover point (UCP) and lower crossover point (LCP) as shown in Figure 19.

Figure 19. Difference count (delta) vs. finger position

Sensor signal values at points a, b, c, and d are expected to be at approximately the same level. If the values are slightly different, consider the lowest value as the UCP.

Sensor signal values at points q, r, and s are expected to be at approximately the same level. If the values are slightly different, consider the lowest value as the LCP.

Figure 20. Difference count (delta) vs. finger position

Slider segment	Peak-to-peak noise (CY8CPROTO-040T)
SNS0	21
SNS1	24
SNS2	25
SNS3	25
SNS4	27

Stage 4: Fine-tune sensitivity to improve SNR

To ensure reliable operation, the sensor should be tuned to have a minimum SNR of 5:1 and a minimum Signal of 50 . The sensitivity can be increased by increasing number of sub-conversions and noise can be decreased by enabling filters.

The steps for optimizing these parameters are as follows:

Ensure that all UCPs meet at least 5:1 SNR (using Equation 1) and all LCPs are greater than twice the peak-to-peak noise for all slider segments.

** Equation 1. SNR equation**
If the SNR is less than 5:1, increase the number of sub-conversions. Edit the number of sub-conversions (N_sub) directly in the Widget/Sensor parameters tab of the CAPSENSE™ Tuner.

Note: Number of sub-conversion should be greater than or equal to 8.
Load the parameters to the device and measure SNR as mentioned in Steps 3 and 4 in the Obtain crossover point and noise section.

Repeat steps 1 to 3 until the following conditions are met:
- Measured SNR from the previous stage is greater than 5:1
- Signal count is greater than 50

If the system is very noisy (>40% of signal), enable filters.

This example has the CIC2 filter enabled, 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. Whenever CIC2 filter is enabled, it is recommended to enable the IIR filter for optimal noise reduction. Therefore, this example has the IIR filter enabled as well.

Open CAPSENSE™ Configurator from ModusToolbox™ Quick Panel and select the appropriate filter:

Figure 21. Filter settings in CAPSENSE™ Configurator

Enable the filter based on the type of noise in your system. See AN85951 – PSoC™ 4 and PSoC™ 6 MCU CAPSENSE™ design guide for more details.
Click Save and close CAPSENSE™ Configurator. Program the device to update the filter settings.

Note : Increasing number of sub-conversions and enabling filters will increase the scan time which in turn decreasing the responsiveness of the sensor. Increase in scan time also increases the power consumption. Therefore, the number of sub-conversions and filter configuration must be optimized to achieve a balance between SNR, power, and refresh rate.

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 as follows.

Set the recommended threshold values for the Slider widget using the LCP and UCP obtained in Stage 5:
- Finger threshold = 80% of UCP
- Noise threshold = Twice the peak-to-peak noise
- Negative noise threshold = Twice the peak-to-peak noise
- Hysteresis = 10% of UCP
- Debounce = Default value of '3'
Set the threshold parameters in the Widget/Sensor Parameters section of the CAPSENSE™ Tuner:

Figure 22. Widget threshold parameters
Click Apply to Device to apply the settings to the device and to the project.

Figure 23. Apply settings to device

After applying the configuration, test the performance by touching the slider. If your sensor is tuned correctly, you will observe the touch status go from 0 to 1 in the Status panel of the Graph View tab as shown in Figure 24. The status of the slider is also indicated by LED2 in the kit; LED2 turns ON when the finger touches the slider and turns OFF when the finger is removed.

Figure 24. Sensor status in CAPSENSE™ Tuner
Click Apply to project as shown in Figure 25. The change is updated in the design.cycapsense file. Close CAPSENSE™ Tuner and launch CAPSENSE™ Configurator. You should see all the changes made in the CAPSENSE™ Tuner are reflected in the CAPSENSE™ Configurator.

Figure 25. Apply settings to Project

Table 5. Software tuning parameters obtained based on sense for CY8CPROTO-040T

Parameter CY8CPROTO-040T

Signal 291

Finger threshold 232

Noise threshold 54

Negative noise threshold 54

Hysteresis 29

ON debounce 3

Low baseline reset 30

Parameter	CY8CPROTO-040T
Signal	291
Finger threshold	232
Noise threshold	54
Negative noise threshold	54
Hysteresis	29
ON debounce	3
Low baseline reset	30

Process time measurement

To set the optimum refresh rate of each power mode, measure the process time of the application.

Perform the following steps to measure the process time of the blocks in the application code while excluding the scan time:

Enable ENABLE_RUN_TIME_MEASUREMENT macro in main.c as follows:
```
#define ENABLE_RUN_TIME_MEASUREMENT (1u)
```
This macro enables the System tick configuration and runtime measurement functionalities.

Place the start_runtime_measurement() function call before the application code and the stop_runtime_measurement() function call after it. The stop_runtime_measurement() function will return the execution time in microseconds (µs).

   #if ENABLE_RUN_TIME_MEASUREMENT
      uint32_t run_time = 0;
      start_runtime_measurement();
   #endif

   /* User Application Code Start */
   .
   .
   .
   /* User Application Code Stop */

   #if ENABLE_RUN_TIME_MEASUREMENT
      run_time = stop_runtime_measurement();
   #endif

Run the application in debug mode with breakpoints placed at the active_processing_time and alr_processing_time variables as follows:

   #if ENABLE_RUN_TIME_MEASUREMENT
      active_processing_time=stop_runtime_measurement();
   #endif
   and 
   #if ENABLE_RUN_TIME_MEASUREMENT
      alr_processing_time=stop_runtime_measurement();
   #endif

Read the variables by adding them into Expressions view tab.

Update related macros with earlier measured processing times in main.c as follows:

#define ACTIVE_MODE_PROCESS_TIME     (xx)

#define ALR_MODE_PROCESS_TIME        (xx)

Scan time measurement

Scan time is necessary to calculate the refresh rate of the application power modes. The total scan time of all the widgets in this code example is 49 µs.

The scan time can be calculated as follows:

The scan time includes the MSCLP initialization time, Cmod, and the total sub-conversions of the sensor.

To control the Cmod initialization sequence, set the "Enable Coarse initialization bypass" configurator option as listed in the following table:

Table 6: Enable coarse initialization bypass

Enable coarse initialization bypass	Behavior
TRUE	Cmod initialization happens only once before scanning the sensors of the widget
FALSE	Cmod initialization happens before scanning each sensor of the widget

Use the following equations to measure the widgets scan time based on coarse initialization bypass options selected:

** Equation 2. Scan time calculation of a widget with coarse initialization bypass enabled**

** Equation 3. Scan time calculation of a widget with coarse initialization bypass disabled**

where,

$n$ - Total number of sensors in the widget

$N_{init}$ - Number of init sub-conversions

$N_{sub}$ - Number of sub-conversions

$SnsClkDiv$ - Sense clock divider

$F_{mod}$ - Modulator clock frequency

$k$ - Measured Initialization time (MSCLP+Cmod).

This value of $k$ measured for this application is ~10 µs. It remains constant for all widgets.

$k$ can be measured using oscilloscope, as shown in Figure 26.

Figure 26. $k$ value measurement

Update the following macros in main.c using the calculated scan time. For this application, the value remains the same for both macros.

#define ACTIVE_MODE_FRAME_SCAN_TIME     (xx)

#define ALR_MODE_FRAME_SCAN_TIME        (xx)

Note : If the application has more than one widget, add the scan time of individual widgets calculated.

Debugging

You can debug this project to step through the code. In the Eclipse IDE for ModusToolbox, 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.

By default, the debug option is disabled in the device configurator. To enable the debug option, see the Setup VDD and Debug mode section. To achieve low power consumption, it is recommended to disable it.

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.

Design and implementation

The project contains a slider 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 on-board KitProg, which in turn enables reading the CAPSENSE™ raw data by the CAPSENSE™ tuner. See EZI2C - Peripheral settings.

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 slider is indicated by an LED in the Prototyping Kit; the LED2 is turned ON when the finger touches the slider and turned OFF when the finger is removed from the slider.

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 27.

Figure 27. 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 follows:

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

Resources and settings

Figure 29. EZI2C settings

Table 7. 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_USER_LED2, CYBSP_USER_BTN	To show the slider operation

Firmware flow

Figure 30. 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™ Middleware Library - CAPSENSE™ library and documents
Tools	ModusToolbox™ – ModusToolbox™ 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: CE238819 - PSoC™ 4: MSCLP low-power CSX slider tuning

Version	Description of change
1.0.0	New code example.
2.0.0	Major update to support ModusToolbox™ v3.2 and CAPSENSE™ Middleware v5.0. This version is not backward compatible with previous versions of ModusToolbox™ software.

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