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PSOC™ 4: MSCLP inductive sensing touch-over-metal keypad-4 demo

This code example demonstrates the implementation of inductive sensing based touch-over-metal (ToM) keypad buttons using SmartSense. This low-power application showcases recommended power states and transitions and the SmartSense based tuning flow for inductive sensing based buttons. This example uses the multi-sense low-power (MSCLP: fifth-generation low-power) inductive sensing technology to demonstrate different considerations to implement a low-power design.

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Requirements

  • ModusToolbox™ v3.4 or later

    Note: This code example version requires ModusToolbox™ v3.4 and is not backward compatible with v3.4 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 v6.22 (ARM)
  • IAR C/C++ Compiler v9.50.2 (IAR)

Supported kits (make variable '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 VDD at 3.3 V.

Software setup

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

This example requires ModusToolbox™ CAPSENSE™ and Multi-Sense Pack to be installed.

Using the code example

Create the project

The ModusToolbox™ tools package provides the Project Creator both as 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 "mtb-example-msclp-isx-tom-keypad-4-buttons-demo" application with the desired name "CY8CPROTO_040T_MS_demo" configured for the CY8CPROTO-040T BSP into the specified working directory, C:/mtb_projects:

project-creator-cli --board-id CY8CPROTO-040T-MS --app-id mtb-example-msclp-isx-tom-keypad-4-buttons-demo --user-app-name CY8CPROTO_040T_MS_demo --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 USB cable between the CY8CPROTO-040T-MS kit and the PC with the keypad-4 extension board, as shown in Figure 1.

    Figure 1. Connecting the CY8CPROTO-040T-MS kit with the USB cable

  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 TOOLCHAIN=<toolchain>

    Example:

    make program TOOLCHAIN=GCC_ARM

  3. After programming, the application starts automatically.

  4. Press any of the sensors with your finger; LEDs turn ON, indicating the activation of different ISX sensors as shown in Figure 2.

    Figure 2. Press the CY8CPROTO-040T-MS kit with the PC

    Table 1. LED states for different sensors

    Sensor LED indication
    ISX button 1 LED D1 turns ON
    ISX button 2 LED D2 turns ON
    ISX button 3 LED D3 turns ON (see note below)
    ISX button 4 LED D4 turns ON

    All LEDs will be OFF when none of the sensor buttons are pressed.

    Note: When pressing ISX button 3, the LED D3 on the expansion board and LED3 on the control board will both turn ON because they share the same GPIO pin (P3.0).

Monitor data using CAPSENSE™ Tuner

  1. Open the 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 located 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 status LED is ON and not blinking; this indicates that the onboard KitProg3 is in CMSIS-DAP Bulk mode. See the 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 as shown in Figure 3.

    Figure 3. Tuner communication setup

    Select I2C under KitProg3 and configure it as follows:

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

    These are the same values set in the EZI2C resource as shown in Figure 4.

    Figure 4. Tuner Communication Setup parameters

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

    Figure 5. Establish connection

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

    Figure 6. Start Tuner communication

    The Widget/Sensor Parameters tab is 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 notice that the pressed widget is highlighted in blue as shown in Figure 7.

    Figure 7. Widget view of the CAPSENSE™ Tuner

  7. Go to the Graph View tab to view the raw count, baseline, difference count, and status of each sensor. To view the sensor data for the different ISX buttons, select Button0_Rx0_Lx0 under Button0 and so on, respectively (see Figure 8).

    Figure 8. Graph view of the CAPSENSE™ Tuner for the ISX button

  8. Observe that the low-power widget sensor (LowPower0_Rx0_Lx0) raw count is plotted after the device completes the full frame scan (or detects a press) in WoT mode and moves to Active/ALR mode.

    Figure 9. Graph view of the CAPSENSE™ Tuner for the low-power widget

  9. See the Widget/Sensor parameters section in the CAPSENSE™ Tuner window as shown in Figure 7.

  10. Switch to the SNR Measurement tab for measuring the signal-to-noise ratio (SNR) and verify that the SNR is greater than 10:1, and the signal count is above 50; select the Button0 widget and Button0_Rx0_Lx0 sensor, and then click Acquire noise as shown in Figure 10.

    Figure 10. CAPSENSE™ Tuner - SNR measurement: Acquire noise


    Note: Because the scan refresh rate is lower in ALR and WoT mode, it takes more time to acquire noise. Press any of the ISX buttons on the keypad-4 expansion board before clicking Acquire noise to transition the device to Active mode to receive the signal faster.


  11. Once the noise is acquired, press the finger/force touch meter at the required position on the button and click Acquire signal. Ensure that the finger/force touch meter remains on the button as long as the signal acquisition is in progress. Observe that the SNR is greater than 10:1 and the signal count is above '50'.

    The calculated SNR on this button is displayed as shown in Figure 11. Based on the end system design, test the signal with a finger press force that matches the size and pressure of a normal use case. Also, test using lighter presses that will be rejected by the system to ensure that they do not reach the finger threshold.

    Figure 11. CAPSENSE™ Tuner - SNR measurement: Acquire signal

    Table 2. SNR values for the regular widgets for the keypad-4 board

    Sensor SNR for 3N force
    Button0 18
    Button1 33
    Button2 17
    Button3 17

  1. To measure the SNR of the low-power sensor (LowPower0_Rx0_Lx0), set the Finger threshold to max (65535) in Widget/Sensor Parameters as shown in Figure 12 for all widgets. This is required to stop detecting a touch in low-power mode and ALR mode and to avoid state transitions to Active mode from both low-power mode and ALR mode. To perform this, set the tuning mode for the regular widgets to SMARTSENSE - HW parameter via the CAPSENSE™ Configurator temporarily (as shown in Figure 17) and program the device.

    Use the Apply to Device option to set the modified parameters to the device instantaneously. But make the final configuration using the CAPSENSE™ Configurator.

    Figure 12. CAPSENSE™ update finger threshold

    Figure 13. Apply changes to device


  2. Repeat steps 10 and 11 to observe the SNR and signal count as shown in Figure 14.

    Figure 14. CAPSENSE™ Tuner - SNR measurement: low-power widget

    Table 3. SNR values for the low power widgets for the keypad-4 board

    Sensor SNR for 3N force
    LowPower0 26
    LowPower1 29
    LowPower2 13
    LowPower3 16

Operation at other voltages

CY8CPROTO-040T-MS kit supports operating voltages of 1.8 V, 3.3 V, and 5 V. See the kit user guide to set the preferred operating voltage and see section Setup the VDDA supply voltage and debug mode in Device Configurator.

The functionalities of this application is optimally tuned for 3.3 V. Observe that the basic functionalities work across other voltages.

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

Tuning procedure

Create custom BSP for your board

  1. Follow the steps mentioned in ModusToolbox™ BSP Assistant user guide to create a custom BSP for your board having any device. In this code example, it is created for the CY8C4046LQI-T452 device.

  2. Open the design.modus file from {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 in the following sections.


Note: See the "Tuning the inductive-sensing solution" section in the AN239751 – Flyback inductive sensing (ISX) design guide and the "Selecting CAPSENSE™ hardware parameters" section in AN85951 – PSOC™ 4 and PSOC™ 6 CAPSENSE™ design guide to learn about the considerations for selecting each parameter value. In addition, see the "Low-power Widget parameters" section in AN234231 – Achieving lowest-power capacitive sensing with PSOC™ 4000T for more details about the considerations for parameter values specific to low-power widgets.

Figure 15. Low-power widget tuning flow

Do the following to tune the button widget

Stage 1: Set the initial configuration

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

  2. Launch the Device Configurator tool.

    Launch the Device Configurator in Eclipse IDE for ModusToolbox™ from the Tools section in the IDE Quick Panel or Standalone mode from the {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 located in the {Application root directory}/bsps/TARGET_APP_<BSP-NAME>/config folder.

  3. Enable the CAPSENSE™ channel in Device Configurator as shown in the Figure 16 and save the changes.

    Figure 16. Enable CAPSENSE™ in Device Configurator


  1. Launch the CAPSENSE™ Configurator tool.

    To launch the 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.

    The tool is launched in a 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 located in the {Application root directory}/bsps/TARGET_APP_<BSP-NAME>/config folder.

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

  2. In the Basic tab, configure the Button widgets and low-power widgets as ISX RM. Set the Tuning Mode as SmartSense - HW parameters for the low power widgets and SMARTSENSE - Full for the regular widgets as shown in Figure 17.

    In the SmartSense - HW parameters mode, set the thresholds manually.

    In the SMARTSENSE - Full mode, set the thresholds using the middleware. However, this mode is not available for low-power widgets.

    Keep the touch sensitivity at its default value of 0.16 uH. The touch sensitivity is the minimum delta in inductance that the system is tuned for by SmartSense.

    Figure 17. CAPSENSE™ Configurator - basic tab


  3. Add/select the following in the General tab under the Advanced tab:

    • Select CAPSENSE™ IMO Clock frequency as 46 MHz.
    • Set the Modulator clock divider to 1 to obtain the maximum available modulator clock frequency.
    • Set the Number of init sub-conversions based on the hint shown when you hover over the edit box. Retain the default value.
    • 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.
    • Set the Number of frames in Wake-on-Touch as the maximum number of frames to be scanned in Wake-on-Touch (WoT) mode if there is no touch detected. This determines the maximum time that 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 shown in Table 4.

    Table 4. 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 18. CAPSENSE™ Configurator – general settings

    • Retain the default settings for all regular and low-power widget filters. To enable or update the filters later depending on the SNR requirements in Stage 2: Fine-tune for required SNR, power, and refresh rate. The 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.

  4. Go to the ISX settings tab and make the following changes:

    • Raw count calibration level (%) helps to achieve the required CDAC calibration levels (35% of maximum count by default) for all sensors in the widget, while maintaining the same sensitivity across the sensor elements.

      Figure 19. CAPSENSE™ Configurator - advanced CSD settings


  5. Go to the Advanced > Widget Details tab. Select LowPower0 from the left pane and set the following:

    • Touch Sensitivity: Retain the default value (this will be set in Stage 2: Fine-tune for required SNR, power, and refresh rate)

    • Clock source: Direct

    • Finger threshold: 65535

      Finger threshold is set to maximum to avoid waking up the device from the WoT mode due to touch detection; this is required to find the signal and SNR.

    • Noise threshold: 10

    • Negative noise threshold: 10

    • Low baseline reset: 10

    • ON debounce: 3

      These threshold values reduce the influence of the baseline on the sensor signal that helps to get the true difference count. These parameters are set in Stage 3: Tune threshold parameters.

      Next, select the other widgets from the left pane and repeat the same configuration for that sensor as well.

      Figure 20. CAPSENSE™ Configurator – Widget Details tab


  6. Go to the Scan Configuration tab to select the pins and the scan slots. Perform the following:

    • Configure pins for the electrodes using the drop-down menu.

    • Configure the scan slots using the Auto-assign slots option. The other option is to allot each sensor a scan slot-based on the entered slot number.

    • Check the notice list for warnings or errors.

      Figure 21. Scan configuration tab


  7. Click Save to apply the settings.

Stage 2: Fine-tune for required SNR, power, and refresh rate

Tune the sensor to have a minimum SNR of 10:1 and a minimum signal of 50 to ensure reliable operation. Increase the sensitivity by decreasing the touch sensitivity value (it is the minimum delta inductance that the system should detect) in the configurator and decrease noise by enabling filters. The touch sensitivity in this code example is set at 0.1 uH.

  1. Measure the SNR as mentioned in the Operation section for all widgets.

  2. If the SNR is less than 10:1, decrease the touch sensitivity value.

  3. Load the parameters to the device and measure the SNR again.

    Repeat steps 1 to 3 until the following conditions are met:

    • Measured SNR from the previous stage is greater than 10:1
    • Signal count is greater than 50

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

    This example has the CIC2 filter enabled, which increases the resolution for the same scan time. See the AN234231 - Achieving lowest-power capacitive sensing with PSOC™ 4000T for detailed information on the CIC2 filter. Whenever a 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.

Stage 3: Tune threshold parameters

In the SMARTSENSE - HW parameter tuning mode, the various thresholds, relative to the signal, need to be set for each low-power widget. For the regular widgets, the threshold parameters are automatically set by the SMARTSENSE - Full tuning mode.

Perform the following in CAPSENSE™ Tuner to set up the thresholds for a low-power widget:

  1. Switch to the Graph View tab and select LowPower0.

  2. For the LowPower0 low-power widget, configure the finger threshold to 65535 and wait for the application to enter Low-power mode. As the finger threshold is set to maximum, pressing the low-power button will not switch the application to Active mode. To do this, set the tuning mode for the regular widgets to SMARTSENSE - HW parameter via the CAPSENSE™ Configurator temporarily and program the device.

  3. Press the sensor and monitor the touch signal in the Sensor signal graph, as shown in Figure 23.

    Figure 23. Sensor signal when the sensor is touched


  4. Note the signal measured and set the thresholds according to the following recommendations:

    • Finger threshold: 80% of the signal

    • Noise threshold: 40% of the signal

    • Negative noise threshold: 40% of the signal

    • Debounce 3

  5. Set the threshold parameters in the Widget/Sensor parameters section of the CAPSENSE™ Tuner.

    Figure 24. Widget threshold parameters


    Table 5. Sensor tuning parameters obtained for CY8CPROTO-040T-MS kit for LowPower0

    Parameter LowPower0
    Signal 100
    Finger threshold 40
    Noise threshold 40
    Negative noise threshold 40
    Low baseline reset 30
    ON debounce 3

  1. Apply the settings to the device by clicking Apply to Device.

    Figure 25. Apply settings to device


    After applying the configuration, test the performance by touching the button. 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 26. The status of the button is also indicated by LED2 in the kit; LED2 turns ON when the finger touches the button and turns OFF when the finger is removed.

    Figure 26. Sensor status in CAPSENSE™ Tuner


  2. Click Apply to Project as shown in Figure 27. The change is updated in the design.cycapsense file. Close CAPSENSE™ Tuner and launch CAPSENSE™ Configurator. All the changes in the CAPSENSE™ Tuner reflects in the CAPSENSE™ Configurator.

    Figure 27. Apply settings to Project


Process time measurement

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

Follow these steps to measure the process time of the blocks of application code while excluding the scan time.

  1. 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.

  2. Place the start_runtime_measurement() function call before your 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

  3. Run the application in the 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

  4. Read the variables by adding them into the Expressions view tab.

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

    #define ACTIVE_MODE_PROCESS_TIME     (xx)

#define ALR_MODE_PROCESS_TIME        (xx)

Scan time measurement

The scan time is also required for calculating the refresh rate of the application power modes. The total scan time of all the widgets in this code example is 16 µs.

It 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 1. Scan time calculation of a widget with coarse initialization bypass enabled

Equation 2. 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

$SnsClkDiv$ = The Lx clock divider for the widget

$F_{mod}$ = 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.

Measure the value of $k$ using an oscilloscope as shown in Figure 28.

Figure 28. $k$ value measurement

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

#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 times of individual widgets calculated.

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.

Design and implementation

The design has a ratiometric implementation of the following sensors:

  • Four Wake-on-Touch widget (4 elements), also called "Low-power Widget"
  • Four inductive sensing based button widgets (4 elements)

Following are the four LEDs used in this project:

  • LEDs D0 to D3 show the buttons' touch status. They are turned ON when the corresponding button is pressed and turned OFF when the finger is lifted.

There are three power states defined for this project:

  • Active mode

  • Active-low refresh rate (ALR) mode

  • Wake-on-Touch (WoT) mode

After reset, the device is in Active mode, and scans the regular CAPSENSE™ widgets with a high refresh rate (128 Hz). If user activity is detected in any other mode, the device is transferred to Active mode to provide the best user interface experience. This mode has the highest power consumption; therefore, the design should reduce the time spent in Active mode.

If there is no user activity for a certain period of time (ACTIVE_MODE_TIMEOUT_SEC = 10 s), the application transitions to ALR mode. Here, the refresh rate is reduced to 32 Hz and therefore, this mode acts as an intermediate state before moving to the lowest-power mode (WoT mode). This mode can also be used for periodically updating the baselines of sensors while there is no user activity for a long time.

Further non-activity for a certain time span (ALR_MODE_TIMEOUT_SEC = 5 s) transitions the application to the lowest-power mode, called the Wake-on-Touch mode, which scans the low-power widget at a low refresh rate (16 Hz) and processes the results without CPU intervention.

Note: An internal low-power timer (MSCLP timer) is available in CAPSENSE™ MSCLP hardware to set the refresh rate for each power mode as follows:

  • For Active and ALR modes: Use the Cy_CapSense_ConfigureMsclpTimer() function.
  • For WoT mode: Use the Wake-on-Touch scan interval in CAPSENSE™ Configurator.

Different power modes and transition conditions for a typical use case are shown in Figure 29.

Figure 29. State machine showing different power states of the device

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 and AN239751 - Flyback inductive sensing (ISX) 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 a Serial Communication Block (SCB) block configured in EZI2C mode to establish communication with the onboard KitProg, which in turn enables reading the CAPSENSE™ raw data using 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™.

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

  1. Open Device Configurator from the Quick Panel.

  2. Go to the System tab, select the Power resource, and set the VDDA value under Operating conditions as shown in Figure 30.

    Figure 30. Setting the VDDA supply in System tab of Device Configurator


  1. By default, the Debug mode is disabled for this application to reduce power consumption. Enable the Debug mode to enable SWD pins as shown in Figure 31.

    Figure 31. Enable the Debug mode in the System tab of Device Configurator


Resources and settings

Figure 32. EZI2C settings


Table 7. Application resources

Resource Alias/object Purpose
SCB (I2C) (PDL) CYBSP_EZI2C EZI2C slave driver to communicate with CAPSENSE™ Tuner
CAPSENSE™ CYBSP_MSC CAPSENSE™ driver to interact with the MSC hardware and interface the CAPSENSE™ sensors

Firmware flow

Figure 33. Firmware flowchart

Related resources

Resources Links
Application notes AN79953 – Getting started with PSOC™ 4 MCU
AN234231 – Achieving lowest-power capacitive sensing with PSOC™ 4000T
AN85951 – PSOC™ 4 and PSOC™ 6 MCU CAPSENSE™ design guide
AN239751 – Flyback inductive sensing (ISX) design guide
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-pdl-cat2 – PSOC™ 4 Peripheral Driver Library (PDL)
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: CE240146 – PSOC™ 4: MSCLP inductive sensing touch-over-metal keypad-4 demo

Version Description of change
1.0.0 New code example
2.0.0 Major update to support ModusToolbox™ v3.3. This version is not backward compatible with previous versions of ModusToolbox™
2.1.0 Major update to support ModusToolbox™ v3.4. This version is not backward compatible with previous versions of ModusToolbox™. Added SmartSense support.

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