PSoC™ 4: CAPSENSE™ liquid-tolerant hybrid scan

This code example demonstrates the self-capacitance scanning technique to implement liquid tolerance on mutual-cap sensors.

CAPSENSE™ senses the self-capacitance of Tx and Rx nodes of a mutual-capacitance sensor. This ability of scanning the sensor using both self-capacitance (CSD) and mutual-capacitance (CSX) sensing modes is used to avoid false triggers due to the presence of liquid drops on a mutual-capacitance sensor.

View this README on GitHub.

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Requirements

• ModusToolbox™ v3.1 or later (tested with v3.1)
• Board support package (BSP) minimum required version: 3.1.0
• Programming language: C
• Associated parts: PSoC™ 4000S, PSoC™ 4100S Plus, PSoC™ 4100S Max, PSoC™ 4000T, and PSoC™ 4500S

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™ 4100S Max Pioneer kit (CY8CKIT-041S-MAX) – Default value of TARGET
• PSoC™ 4100S Plus Prototyping Kit (CY8CKIT-149)
• PSoC™ 4000S CAPSENSE™ Prototyping Kit (CY8CKIT-145-40XX)
• PSoC™ 4000T CAPSENSE™ Prototyping Kit (CY8CPROTO-040T)
• PSoC™ 4500S Pioneer Kit (CY8CKIT-045S)

Hardware setup

This example uses the board's default configuration. See the kit guide to ensure that the board is configured correctly.

Note: Some of the PSoC™ 4 kits ship with KitProg2 installed. The 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 If you do not upgrade, you will see an error like "unable to find CMSIS-DAP device" or "KitProg firmware is out of date".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

This example requires no additional software or tools.

Using the code example

Create the project

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

Use Project Creator GUI

1. Open the Project Creator GUI tool.

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

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

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

3. On the Select Application page:

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

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

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

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

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

   d. Click Create to complete the application creation process.

Use Project Creator CLI

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

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

The following example clones the "mtb-example-psoc4-capsense-liquid-tolerant-hybrid-scan" application with the desired name "Capsenseliquidtoleranthybridscan" configured for the CY8CKIT-041S-MAX BSP into the specified working directory, C:/mtb_projects:

project-creator-cli --board-id CY8CKIT-041S-MAX --app-id mtb-example-psoc4-capsense-liquid-tolerant-hybrid-scan --user-app-name Capsenseliquidtoleranthybridscan --target-dir "C:/mtb_projects"

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

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

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

Open the project

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

Eclipse IDE

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

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

Visual Studio (VS) Code

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

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

Keil µVision

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

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

IAR Embedded Workbench

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

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

Command line

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

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

Operation

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

2. Program the board using one of the following:

   Using Eclipse IDE

   1. Select the application project in the Project Explorer.

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

   In other IDEs

   Follow the instructions in your preferred IDE.

   Using CLI

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

   make program TOOLCHAIN=<toolchain>
   

   Example:

   make program TOOLCHAIN=GCC_ARM
   

3. Touch any of the CAPSENSE™ buttons with your finger. Corresponding LEDs turn ON indicating the activation of buttons.

4. Use a water dropper to place water droplets on top of the buttons. Observe that all LEDs are in OFF state indicating that no false trigger occurs due to the presence of water.

5. Touch any of the buttons with your finger in the presence of water droplets and observe that corresponding LEDs turn ON.

6. 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 the {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_<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 the kit is in CMSIS-DAP bulk mode (KitProg3 Status LED is ON and not blinking). See Firmware-loader to learn on 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 that appears, select the I2C checkbox under KitProg3 and configure as follows:

      • I2C address: 8
      • Sub-address: 2 bytes
      • Speed (kHz): 100

      These are the same values set in the EZI2C resource.

      Figure 1. Tuner Communication Setup parameters

      

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

      Figure 2. Tuner Communication Setup parameters

      

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

      Figure 3. 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; you can see the Button0 widget highlighted in blue color when you touch it.

      Figure 4. Widget View tab of 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 Button 1, select Button1_Rx0 under Button1.

      Figure 5. Graph View of CAPSENSE™ Tuner

      

   8. Observe the Widget/Sensor Parameters section in the CAPSENSE™ Tuner window as shown in Figure 5.

   9. Switch to the SNR Measurement tab for measuring the SNR and verify that the SNR is above 5:1, select Button1 and Button1_Rx0 sensor, and then click Acquire Noise as Figure 6 shows.

      Figure 6. CAPSENSE™ Tuner - SNR Measurement: Acquire Noise

      

   10. Once the noise is acquired, place the metal finger at a position on the button and then click Acquire Signal. Ensure that the metal finger remains on the button as long as the signal acquisition is in progress. Observe the SNR is above 5:1.

       The calculated SNR on this button is displayed, as Figure 7 shows. Based on your end system design, test the signal with a finger that matches the size of your normal use case. Typically, finger size targets are ~8 to 9 mm. Consider testing with smaller sizes that should be rejected by the system to ensure that they do not reach the finger threshold.

       Figure 7. CAPSENSE™ Tuner - SNR Measurement: Acquire Signal

       

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 project contains button widgets configured in CSX-RM sensing mode. In the default setting, all inactive sensors of the buttons are connected to the shield when a sensor is scanned. In this code example, callback to the CAPSENSE™ middleware is registered using the Cy_CapSense_RegisterCallback function. To achieve liquid tolerance, the Rx electrode of the sensor with the CSD sense method should be scanned. While scanning the Rx electrode as a CSD sensor, ensure that the shield electrode is enabled, and connect the Tx pin of the mutual-capacitance sensor to the driven shield signal. The low-level CapSense_SetPinState() API function is used to connect the Tx pin of the mutual-capacitance sensor to the shield electrode.

Note: Use the low-level Cy_CapSense_SlotPinState() API to connect the mutual-capacitance sensor's Tx pin to the shield electrode for fifth-generation low-power CAPSENSE™.

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

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

The CAPSENSE™ data structure that contains the CAPSENSE™ raw data is exposed to 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™.

Resources and settings

Figure 8. EZI2C - Peripheral settings

The following ModusToolbox™ resources are used in this example:

Table 1. Application resources

Resource	Alias/object	Purpose
CAPSENSE™	CYBSP_CapSense	CAPSENSE™ driver to interact with the CSX hardware and interface the CAPSENSE™ sensors
SCB	EZI2C	EZI2C driver to interface with CAPSENSE™ tuner
LED (BSP)	CYBSP_USER_LED	User LED to show the output

Firmware flow

Figure 9. Firmware flowchart

Related resources

Resources	Links
Application notes	AN79953 – Getting started with PSoC™ 4 AN85951 – PSoC™ 4 and PSoC™ 6 MCU CAPSENSE™ 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 page
Libraries on GitHub	mtb-pdl-cat2 – PSoC™ 4 Peripheral Driver Library (PDL) mtb-hal-cat2 – Hardware abstraction layer (HAL) library
Tools	ModusToolbox™ – ModusToolbox™ is a collection of easy-to-use software and tools enabling rapid development with Infineon MCUs, covering applications from embedded sense and control to wireless and cloud-connected systems using AIROC™ Wi-Fi and Bluetooth® connectivity devices.

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: CE237675 – PSoC™ 4: CAPSENSE™ liquid-tolerant hybrid scan

Version	Description of change
1.0.0	New code example.
1.1.0	Added support for new BSPs

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