PSOC™ 4: MSCLP capacitive and inductive sensing buttons

This code example demonstrates the implementation of inductive sensing based touch-over-metal (ToM) keypad buttons using SmartSense along with a CSD button and a CSX button on a PSOC™ 4 device featuring fifth-generation CAPSENSE™ multi-sense converter low power (MSCLP) technology.

The example showcases methods to configure and scan both inductive and capacitive sensing based buttons together, and uses the CAPSENSE™ MSCLP to demonstrate different considerations to implement such a design.

View this README on GitHub.

Provide feedback on this code example.

Requirements

ModusToolbox™ v3.5 or later

Note: This code example version requires ModusToolbox™ v3.5 and is not backward compatible with v3.4 or older versions.
Board support package (BSP) minimum required version: 3.3.0
Programming language: C
Associated parts: PSOC™ 4100T Plus

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')

PSOC™ 4100T Plus CAPSENSE™ Prototyping Kit (CY8CPROTO-041TP) - Default TARGET

Hardware setup

This example uses the board's default configuration. See the kit user guide CY8CPROTO-041TP PSOC™ 4100T Plus CAPSENSE™ Prototyping Kit guide to configure the required operating voltage and to setup the VDDA supply voltage, see Section Set up the VDDA supply voltage and debug mode in Device Configurator.

This application is tuned to perform optimally at the default voltage. However, you can observe the basic functionality at other supported voltages.

Software setup

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

Using the code example

Create the project

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

Use Project Creator GUI

Open the Project Creator GUI tool

There are several ways to do this, including launching it from the dashboard or from inside the Eclipse IDE. For more details, see the Project Creator user guide (locally available at {ModusToolbox™ install directory}/tools_{version}/project-creator/docs/project-creator.pdf)
On the Choose Board Support Package (BSP) page, select a kit supported by this code example. See Supported kits

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

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

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

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

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

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

d. Click Create to complete the application creation process

Use Project Creator CLI

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

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

The following example clones the "mtb-example-psoc4-msclp-csd-csx-isx-buttons" application with the desired name "MSCLP_ISX_Buttons" configured for the CY8CPROTO-041TP BSP into the specified working directory, C:/mtb_projects:

project-creator-cli --board-id CY8CPROTO-041TP --app-id mtb-example-psoc4-msclp-csd-csx-isx-buttons --user-app-name MSCLP_ISX_Buttons --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).

Arm® Keil® µVision®

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

For more details, see the Arm® 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 USB cable between the CY8CPROTO-041TP kit and the PC with the keypad-4 extension board as shown in Figure 1

Figure 1. Connecting the CY8CPROTO-041TP kit with the USB cable
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

Press any of the inductive sensors or the CSD or CSX buttons with your finger; LEDs turn ON, indicating the activation of the corresponding sensors as shown in Figure 2

Figure 2. Press the CY8CPROTO-041TP 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 and LED6 turn ON (see note below)
ISX button 4	LED D4 turns ON
CSD button	LED 3 turns ON
CSX button	LED 2 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 LED6 on the control board will both turn ON because they share the same GPIO pin.

Monitor data using CAPSENSE™ Tuner

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
Ensure that the status LED is ON and not blinking; as it 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
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
Click Connect or select Communication > Connect to establish a connection

Figure 5. Establish connection
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
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. The CAPSENSE™ buttons are tuned to respond to a light finger touch. The ISX buttons are tuned to respond to a finger press with a 3N force

Figure 7. Widget view of the CAPSENSE™ Tuner
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 ISX_Button1_Rx0_Lx0 under ISX_Button1 and so on, respectively (see Figure 8). Similarly for the CAPSENSE™ buttons, select the CSD_Button_Sns0 under CSD_Button and so forth.

Figure 8. Graph view of the CAPSENSE™ Tuner for the ISX button
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 ISX_Button1 widget and ISX_Button1_Rx0_Lx0 sensor, and then click Acquire noise as shown in Figure 9

Figure 9. CAPSENSE™ Tuner - SNR measurement: Acquire noise
Once the noise is acquired, press the finger at the required position on the button and click Acquire signal. Ensure that the finger 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 10. 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. Use a force meter to apply the required force

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

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

Sensor SNR for 3N force / 6 mm button press as applicable

ISX_Button1 42

ISX_Button2 16

ISX_Button3 51

ISX_Button4 66

CSD_Button 5.8

CSX_Button 7.7

Note: For the CAPSENSE™ buttons, a metal finger of 6 mm diameter has been used for tuning

Scanning ISX, CSD, and CSX sensors

As per CAPSENSE™ middleware errata 17158, the ISX scan followed by BIST measurement or with other sensing methods CSD and CSX introduces a drift in raw count, which impacts the performance and accuracy of the ISX scanning.

These are the possible workarounds:

Use ISX in stand-alone mode without other sensing methods. The code example uses the Cy_CapSense_ScanSlots() API to do this. The ISX sensors are scanned separately from the CSD and CSX sensors

/*Scan all slots corresponding to the ISX buttons*/
Cy_CapSense_ScanSlots(0u,4u,&cy_capsense_context);
while(Cy_CapSense_IsBusy(&cy_capsense_context)){}

/*Scan the slots corresponding to the CSD button*/
Cy_CapSense_ScanSlots(4u,1u,&cy_capsense_context);
while(Cy_CapSense_IsBusy(&cy_capsense_context)){}

/*Scan the slots corresponding to the CSX button*/
Cy_CapSense_ScanSlots(5u,1u,&cy_capsense_context);
while(Cy_CapSense_IsBusy(&cy_capsense_context)){}

Use ISX without built-in self-test (BIST) as done in this example
Configure the inactive sensor connection parameter to High-Z for the ISX scanning. This is the default configuration when the ISX sensors are scanned
Introduce a dummy scan before ISX. This can be done by increasing the number of init sub-conversions via the CAPSENSE™ Configurator as shown in Figure 11

Figure 11. Increasing init sub-conversions via CAPSENSE™ Configurator

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 the ModusToolbox™ BSP Assistant user guide
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 follows:

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.

See the following code examples to learn more about the tuning flow for the different widgets:

PSOC™ 4: MSCLP inductive sensing touch-over-metal keypad-4 demo
PSOC™ 4: MSCLP low-power self-capacitance button
PSOC™ 4: MSCLP low-power mutual-capacitance button

Operation at other voltages

CY8CPROTO-041TP 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 5 V, which is the default operating voltage for this kit. Observe that the basic functionalities work across other voltages.

For optimal performance, it is recommended to repeat the tuning procedure if the operating voltage is changed from default.

Debugging

You can debug this project 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™ user guide.

Design and implementation

The design has an implementation of the following sensors:

Four inductive sensing based button widgets (4 elements)
One self-capacitance based button configured as a regular widget (called "Button" in the CAPSENSE™ Configurator) in the CSD-RM sensing mode
One mutual-capacitance based button configured as a regular widget (called "Button" in the CAPSENSE™ Configurator) in the CSX-RM sensing mode

Following are the six LEDs used in this project:

LEDs D0 to D3 show the ISX buttons' touch status. They are turned ON when the corresponding button is pressed and turned OFF when the finger is lifted.
LED 3 shows the CSD button touch status. It is turned ON when the CSD button is touched and turned OFF when the finger is lifted.
LED 2 shows the CSX button touch status. It is turned ON when the CSX button is touched and turned OFF when the finger is lifted.

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) 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 Figure 13 in Resources and settings section for the EZI2C settings used in this code example.

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

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 12

Figure 12. Setting the VDDA supply in System tab of Device Configurator

Resources and settings

Figure 13. EZI2C settings

Table 3. 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 13. Firmware flowchart

Related resources

Resources	Links
Application notes	AN79953 – Getting started with PSOC™ 4 MCU AN234231 – PSOC™ 4 CAPSENSE™ ultra-low-power capacitive sensing techniques 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: CE241366 – PSOC™ 4: MSCLP capacitive and inductive sensing buttons

Version	Description of change
1.0.0	New code example

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