PSoC™ 6 MCU: CAPSENSE™ custom scan

This code example demonstrates CAPSENSE™ custom scanning through callback functions from CAPSENSE™ middleware that allows altering the sensor parameters during runtime or synchronizing the CAPSENSE™ scan with non-CAPSENSE™ operations.

Custom scanning of CAPSENSE™ sensors may require for a few specific applications as follows:

1. Changing the inactive sensor connection based on the sensor being currently scanned

2. Setting different tuning parameters for various sensors within a widget

3. Optimizing the sensor performance by disabling the source of noise when the affected sensors are being scanned

The CAPSENSE™ middleware offers a lot of flexibility in scanning the sensors. In this code example, the callback function is used to change the inactive sensor state to either shield or ground depending on the sensor being scanned. This provides liquid tolerance and reduced parasitic capacitance of the sensor and the shield. It also decreases emissions because the area driven by the shield signal is reduced.

This code example can be extended to many more scenarios. A few examples include the following:

1. To tune each sensor of a widget separately so that the gain/sensitivity can be configured.

   The modulator IDAC for each sensor can be set separately, which in turn adjusts the gain of each sensor in a widget. This can be done by writing the modulator IDAC code for different sensors using Cy_CapSense_SetParam (see CAPSENSE™ middleware library). After the IDAC is set, Cy_CapSense_CSDSetUpIdacs must be called to configure the IDAC registers. Because each sensor in a widget cannot be configured individually, this method can be used to tune each sensor’s gain.

2. When external electrical noises affect CAPSENSE™ operation.

   If a high-speed switching signal affects a few sensors in the system, the firmware can turn off such sources of noise while the affected sensors are scanned. This would help with better CAPSENSE™ operation while keeping all other operations as functional as possible.

View this README on GitHub.

Provide feedback on this code example.

Requirements

• ModusToolbox™ software v3.1 or later (tested with v3.1)
• Board support package (BSP) minimum required version: 4.0.0
• Programming language: C
• Associated parts: All PSoC™ 6 MCU parts, AIROC™ CYW43012 Wi-Fi & Bluetooth® combo chip, AIROC™ CYW4343W Wi-Fi & Bluetooth® combo chip, AIROC™ CYW4373 Wi-Fi & Bluetooth® combo chip

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™ 6 Wi-Fi Bluetooth® prototyping kit (CY8CPROTO-062-4343W) – Default value of TARGET
• PSoC™ 6 Wi-Fi Bluetooth® pioneer kit (CY8CKIT-062-WIFI-BT)
• PSoC™ 6 Bluetooth® LE pioneer kit (CY8CKIT-062-BLE)
• PSoC™ 62S2 Wi-Fi Bluetooth® pioneer kit (CY8CKIT-062S2-43012)
• PSoC™ 62S1 Wi-Fi Bluetooth® pioneer kit (CYW9P62S1-43438EVB-01)
• PSoC™ 62S1 Wi-Fi Bluetooth® pioneer kit (CYW9P62S1-43012EVB-01)
• PSoC™ 62S3 Wi-Fi Bluetooth® prototyping kit (CY8CPROTO-062S3-4343W)
• PSoC™ 64 "Secure Boot" Wi-Fi Bluetooth® pioneer kit (CY8CKIT-064B0S2-4343W)
• PSoC™ 62S4 pioneer kit (CY8CKIT-062S4)
• PSoC™ 62S2 evaluation kit (CY8CEVAL-062S2, CY8CEVAL-062S2-LAI-4373M2)

Hardware setup

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

An oscilloscope is required to observe the waveform at the slider segment.

Note: The PSoC™ 6 Bluetooth® LE pioneer kit (CY8CKIT-062-BLE) and the PSoC™ 6 Wi-Fi Bluetooth® pioneer kit (CY8CKIT-062-WIFI-BT) ship with KitProg2 installed. The ModusToolbox™ software 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

Install a terminal emulator if you don't have one. Instructions in this document use Tera Term.

This example requires no additional software or tools.

Using the code example

Create the project and open it using one of the following:

In Eclipse IDE for ModusToolbox™ software

1. Click the New Application link in the Quick Panel (or, use File > New > ModusToolbox™ Application). This launches the Project Creator tool.

2. Pick a kit supported by the code example from the list shown in the Project Creator - Choose Board Support Package (BSP) dialog.

   When you select a supported kit, the example is reconfigured automatically to work with the kit. To work with a different supported kit later, use the Library Manager to choose the BSP for the supported kit. You can use the Library Manager to select or update the BSP and firmware libraries used in this application. To access the Library Manager, click the link from the Quick Panel.

   You can also just start the application creation process again and select a different kit.

   If you want to use the application 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. In the Project Creator - Select Application dialog, choose the example by enabling the checkbox.

4. (Optional) Change the suggested New Application Name.

5. The Application(s) Root Path defaults to the Eclipse workspace which is usually the desired location for the application. If you want to store the application in a different location, you can change the Application(s) Root Path value. Applications that share libraries should be in the same root path.

6. Click Create to complete the application creation process.

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

In command-line interface (CLI)

ModusToolbox™ software provides the Project Creator as both a GUI tool and the command line tool, "project-creator-cli". The 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™ software 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™ software installation instead of a standard Windows command-line application. This shell provides access to all ModusToolbox™ software 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 "project-creator-cli" tool has the following arguments:

Argument	Description	Required/optional
--board-id	Defined in the <id> field of the BSP manifest	Required
--app-id	Defined in the <id> 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

The following example clones the "PSoC™ 6 MCU: CAPSENSE™ custom scan" application with the desired name "Psoc6CapsenseScan" configured for the CY8CPROTO-062-WIFI-BT BSP into the specified working directory, C:/mtb_projects:

project-creator-cli --board-id CY8CPROTO-062-WIFI-BT --app-id mtb-example-psoc6-capsense-custom-scan --user-app-name Psoc6CapsenseScan --target-dir "C:/mtb_projects"

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™ software user guide (locally available at {ModusToolbox™ software install directory}/docs_{version}/mtb_user_guide.pdf).

To work with a different supported kit later, use the Library Manager to choose the BSP for the supported kit. You can invoke the Library Manager GUI tool from the terminal using the make modlibs command or use the Library Manager CLI tool "library-manager-cli" to change the BSP.

The "library-manager-cli" tool has the following arguments:

Argument	Description	Required/optional
--add-bsp-name	Name of the BSP that should be added to the application	Required
--set-active-bsp	Name of the BSP that should be as active BSP for the application	Required
--add-bsp-version	Specify the version of the BSP that should be added to the application if you do not wish to use the latest from manifest	Optional
--add-bsp-location	Specify the location of the BSP (local/shared) if you prefer to add the BSP in a shared path	Optional

Following example adds the CY8CPROTO-062-4343W BSP to the already created application and makes it the active BSP for the app:

~/ModusToolbox/tools_{version}/library-manager/library-manager-cli --project "C:/mtb_projects/Psoc6CapsenseScan" --add-bsp-name CY8CPROTO-062-4343W --add-bsp-version "latest-v4.X" --add-bsp-location "local"

~/ModusToolbox/tools_{version}/library-manager/library-manager-cli --project "C:/mtb_projects/Psoc6CapsenseScan" --set-active-bsp APP_CY8CPROTO-062-4343W

In third-party IDEs

Use one of the following options:

• Use the standalone Project Creator tool:

  1. Launch Project Creator from the Windows Start menu or from {ModusToolbox™ software install directory}/tools_{version}/project-creator/project-creator.exe.

  2. In the initial Choose Board Support Package screen, select the BSP, and click Next.

  3. In the Select Application screen, select the appropriate IDE from the Target IDE drop-down menu.

  4. Click Create and follow the instructions printed in the bottom pane to import or open the exported project in the respective IDE.

• Use command-line interface (CLI):

  1. Follow the instructions from the In command-line interface (CLI) section to create the application.

  2. Export the application to a supported IDE using the make <ide> command.

  3. Follow the instructions displayed in the terminal to create or import the application as an IDE project.

For a list of supported IDEs and more details, see the "Exporting to IDEs" section of the ModusToolbox™ software user guide (locally available at {ModusToolbox™ software install directory}/docs_{version}/mtb_user_guide.pdf).

Operation

If using a PSoC™ 64 "Secure MCU" kit (like CY8CKIT-064B0S2-4343W), the PSoC™ 64 device must be provisioned with keys and policies before being programmed. Follow the instructions in the "Secure Boot" SDK user guide to provision the device. If the kit is already provisioned, copy-paste the keys and policy folder to the application folder.

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

2. Open a terminal program and select the KitProg3 COM port. Set the serial port parameters to 8N1 and 115200 baud.

3. Program the board using one of the following:

   Using Eclipse IDE for ModusToolbox™ software

   1. Select the application project in the Project Explorer.

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

   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 and target are specified in the application's Makefile but you can override those values manually:

   make program TOOLCHAIN=<toolchain>
   

   Example:

   make program TOOLCHAIN=GCC_ARM
   

4. After programming, the application starts automatically. Confirm that "<CE Title>" is displayed on the UART terminal.

5. Slide your finger over the CAPSENSE™ linear slider and observe that the brightness of the LED changes based on the position of the finger.

6. Observe the charging and discharging waveform of the sensors in an oscilloscope by probing the sensor pins before the series resistor. Note that only neighboring sensors to the sensor being scanned are switched with the shield waveform, while other sensors are at ground potential (see Oscilloscope waveforms).

For monitoring CAPSENSE™ data, CAPSENSE™ parameter tuning, and signal-to-noise (SNR) measurement, see CAPSENSE™ tuner guide.

See AN85951 – PSoC™ 4 and PSoC™ 6 MCU CAPSENSE™ design guide for more details on selecting the right tuning parameters.

Note that the CAPSENSE™ parameters must be tuned while running this code example. Tuning the parameters with the default CAPSENSE™ implementation results in different parasitic capacitance of sensor and shield, which provides different tuning results.

Oscilloscope waveforms

Figure 1 shows the oscilloscope waveforms of four sensors in the default scanning implementation. Note that all inactive sensors are always driven to shield. Therefore, there is always a switching signal on all the slider elements for the entire scan duration. Because the area driven to shield is larger, this increases the emissions produced by the CAPSENSE™ operation. This also means that the parasitic capacitance of the shield that needs to be driven by the component is higher.

Figure 1. Sensor waveforms - default implementation

Figure 2 shows the oscilloscope waveforms of four sensors of the linear slider widget with the custom scanning implemented. Note that whenever a sensor is scanned, only the adjacent sensors are driven to shield. All other sensors are connected to the ground, thereby reducing the total area of emission.

Figure 2. Sensor waveforms - custom implementation

a. Sns0 is being scanned, and Sns1 is being driven to shield. All other sensors are connected to the ground.

b. Sns1 is being scanned, and Sns0 and Sns2 (adjacent sensors) are driven to shield. All others are connected to the ground.

c. Sns2 is being scanned, and Sns1 and Sns3 are driven to shield. All other sensors are connected to the ground.

d. Sns3 is being scanned, and Sns2 and Sns4 (not shown in Figure 2 are driven to shield. All other sensors are connected to the ground.

Debugging

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

Note: (Only while debugging) On the CM4 CPU, some code in main() may execute before the debugger halts at the beginning of main(). This means that some code executes twice – once before the debugger stops execution, and again after the debugger resets the program counter to the beginning of main(). See KBA231071 to learn about this and for the workaround.

Design and implementation

In this project, PSoC™ 6 MCU scans a self-capacitance (CSD)-based, 5-element CAPSENSE™ slider with a custom shield implementation. In the default setting, all inactive sensors of the slider are connected to the shield when a sensor is scanned. In this code example, the CY_CAPSENSE_START_SAMPLE_E callback of the CAPSENSE™ middleware is registered using Cy_CapSense_RegisterCallback. This function is called at the beginning of a sensor scan. The function then loops through all the sensors in the widget.

If the sensor is found to be adjacent to the sensor being scanned (obtained as a parameter), the pin state is set to shield; if not, the pin state is set to ground. This is done using the Cy_CapSense_SetPinState API function. This takes the widget ID, sensor ID, the state of the pin (CY_CAPSENSE_SHIELD or CY_CAPSENSE_GROUND, in this case), and the pointer to the CAPSENSE™ context structure as parameters and sets up the status accordingly.

Figure 3 and Figure 4 show the difference between normal scanning and custom scanning with respect to slider segments. The segment shown in red is the actual sensor being scanned, while segments in yellow show sensors driven to the shield. Segments in green are sensors that are connected to the ground.

Figure 3. Normal scanning	Figure 4. Custom scanning

Resources and settings

Table 1. Application resources

Resource	Alias/object	Purpose
CSD	CYBSP_CSD	CAPSENSE™ driver to interface touch sensors
SCB	EZI2C	EZI2C driver to interface with CAPSENSE™ tuner
GPIO (HAL)	CYBSP_USER_LED	User LED

Memory usage

This section captures the memory usage (internal flash and SRAM) of this code example in number of bytes for the default toolchain (GCC_ARM), default target (see Supported kits), and Debug build mode. Note that the memory usage is captured during a release of this code example; it may differ now because dependent libraries may have been updated since then.

Static usage

Application	Flash (in bytes)	SRAM (in bytes)
<APPNAME1>	replace_code_example_flash_usage_<APPNAME1>	replace_code_example_sram_usage_<APPNAME1>
<APPNAME2>	replace_code_example_flash_usage_<APPNAME2>	replace_code_example_sram_usage_<APPNAME2>

Heap usage

Application	Use case description	Heap usage (in bytes)
<APPNAME1>
<APPNAME2>

Related resources

Resources	Links
Application notes	AN228571 – Getting started with PSoC™ 6 MCU on ModusToolbox™ software AN215656 – PSoC™ 6 MCU: Dual-CPU system design AN85951 – PSoC™ 4 and PSoC™ 6 MCU CAPSENSE™ design guide
Code examples	Using ModusToolbox™ software on GitHub
Device documentation	PSoC™ 6 MCU datasheets PSoC™ 6 technical reference manuals
Development kits	Select your kits from the Evaluation board finder
Libraries on GitHub	mtb-pdl-cat1 – PSoC™ 6 peripheral driver library (PDL) mtb-hal-cat1 – Hardware abstraction layer (HAL) library retarget-io – Utility library to retarget STDIO messages to a UART port
Middleware on GitHub	capsense – CAPSENSE™ library and documents psoc6-middleware – Links to all PSoC™ 6 MCU middleware
Tools	Eclipse IDE for ModusToolbox™ software – ModusToolbox™ software 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.

For PSoC™ 6 MCU devices, see How to design with PSoC™ 6 MCU – KBA223067 in the Infineon community.

Document history

Document title: CE230163 - PSoC™ 6 MCU: CAPSENSE™ custom scan

Version	Description of change
1.0.0	New code example
2.0.0	Major update to support ModusToolbox™ software v2.2, added support for new kits This version is not backward compatible with ModusToolbox™ software v2.1
2.1.0	Added support for new kits
2.1.1	Updated to support ModusToolbox™ software v2.3
2.2.0	Added support for CY8CEVAL-062S2 and CY8CEVAL-062S2-LAI-4373M2
3.0.0	Major update to support ModusToolbox™ v3.0. This version is not backward compatible with previous versions of ModusToolbox™
3.1.0	Update to support ModusToolbox™ v3.1 and CAPSENSE™ middleware v4.X

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