PSoC™ 4: CAPSENSE™ low-power

This code example demonstrates an implementation of a low-power CAPSENSE™ design using the PSoC™ 4 MCU. This example features the CAPSENSE™ slider and the buttons. It scans all the widgets and then processes the scanned data. Here the device is put into Deep Sleep in idle mode and the WDT is used to wake up the device from the Deep Sleep mode.

View this README on GitHub.

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Requirements

• ModusToolbox™ software 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 Max, PSoC™ 4100S Plus, 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 Plus Prototyping Kit (CY8CKIT-149) - Default value of TARGET
• PSoC™ 4000S CAPSENSE™ Prototyping Kit (CY8CKIT-145-40XX)
• PSoC™ 4500S Pioneer Kit (CY8CKIT-045S)
• PSoC™ 4100S Max Pioneer Kit (CY8CKIT-041S-MAX)

Hardware setup

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

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 If you do not upgrade, you will see an error like "unable to find CMSIS-DAP device" or "KitProg firmware is out of date".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

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

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

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 "CAPSENSE™ low-power" application with the desired name "CAPSENSE_Low_Power" configured for the CY8CKIT-149 BSP into the specified working directory, C:/mtb_projects:

project-creator-cli --board-id CY8CKIT-149 --app-id mtb-example-psoc4-capsense-low-power --user-app-name CAPSENSE_Low_Power --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. 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

   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
   

4. After programming, the application starts automatically. Confirm that "CE239069 - PSoC™ 4:CAPSENSE™ low-power" is displayed on the UART terminal.

5. The status of onboard user LED will be changed-based on the button or slider segment touch. By default, or during a no-press condition, user LED is turned OFF.

6. Slide your finger along the slider to view the touch position detected on the serial terminal as shown in Figure 1.

   Figure 1. Terminal output displaying the slider position

   

7. Measure the current values as instructed in the making the current measurements for PSoC™ 4 MCU device section.

Monitor data using CAPSENSE™ tuner

1. By Default, CAPSENSE™ tuner is disabled in the code example to achieve low-power. Enable the tuner communication by defining the CAPSENSE_TUNER_ENABLE variable in the Makefile under DEFINES and program the example onto the device.

2. Open CAPSENSE™ tuner from the IDE Quick Panel.

3. Ensure that the kit is in KitProg3 mode. For more details to update the firmware and switch to KitProg3 mode, see Firmware-loader.

4. In the tuner application, click Tuner Communication Setup or select Tools > Tuner Communication Setup. In the popup window, select the I2C checkbox under KitProg3 and configure as follows:

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

   Figure 2. I2C tuner communication setup

   

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

   Figure 3. Establish connection

   

6. Click Start or select Communication > Start.

   Figure 4. Start tuner communication

   

7. Set the Read mode to Synchronized mode. Navigate to the Widget view tab and notice that the Button0 and LinearSlider0 widgets are highlighted in blue when you touch it. In Widget Explorer, select the widgets and sensors to view the Touch Signal Graph.

   Figure 5. Widget view tab of the CAPSENSE™ tuner

   

8. The tuner GUI displays the data from the sensor in the Widget View and Graph View tabs.

9. The CAPSENSE™ tuner can also be used for CAPSENSE™ parameter tuning, and measuring signal-to-noise ratio (SNR). For Manual tuning, see the ModusToolbox™ CAPSENSE™ Tuner guide.

Debugging

For all the kits, the debug port is by default disabled in order to achieve low-power. If debugging is required, do the following:

• Enable the Debug mode under the Systems tab in the Device Configurator and change the Debug mode setting to SWD.
• Select the pins P3[2] (SWDIO) and P3[3] (SWDCK) under the SWD pin setting.
• Select the Drive mode of both the pins as "Strong Drive,Input buffer on" under the Pins tab in the Device Configurator.

You can debug the code example.

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 multiple button widgets and a slider widget configured in CSD sensing mode. See the "CAPSENSE™ CSD sensing method" section in the AN85951 – PSoC™ 4 and PSoC™ 6 MCU CAPSENSE™ design guide for details on CAPSENSE™ CSD and CSX sensing modes.

The sensing elements are mapped to the onboard user buttons and segments of the slider. The status of the CAPSENSE™ buttons and sliders are shown by the LED state and prints the slider position in the serial terminal. The LED turns ON when a button press is registered and remains OFF when the button is not pressed.

See PSoC™ 4 MCU: CAPSENSE™ CSD button tuning code example to tune CSD sensors and PSoC™ 4 MCU: CAPSENSE™ CSX button tuning code example to tune the CSX sensors.

The watchdog timer (WDT) in PSoC™ 4 is a 16-bit timer and uses the internal low-speed oscillator (ILO) clock of 40 kHz as a source. The accuracy of ILO is (- 50% to +100%). Therefore, the match value of WDT is set after compensating the ILO with IMO. The firmware flow is as follows:

1. Enable the ILO, which is the source for the WDT. Start the ILO measurement and get the value of ilo_compensated_counts which must be set after every interrupt match.
2. Write the match value. The WDT can generate an interrupt when the WDT counter reaches the match count. The match count is generated using DESIRED_WDT_INTERVAL.
3. Enable interrupt generation and assign the interrupt service routine(wdt_isr).
4. Enable the WDT. Because the ILO has low accuracy, the ilo_compensated_counts is calculated, and the match value of the WDT is updated following a WDT interrupt.
5. The System is put into Deep Sleep in Idle mode to save power. Because the watchdog timer works on a low-frequency clock (LFCLK), its operation will not be affected when the system is put into Deep Sleep mode. The watchdog timer interrupt will wake the device from Deep Sleep mode.

Note:

1. The WDT is configured to generate interrupts at WDT_INTERRUPT_INTERVAL_MS intervals. The default value of WDT_INTERRUPT_INTERVAL_MS is 10 ms. The WDT generates an interrupt on reaching the match value. The WDT counter is not reset on a match; it continues to count across the full 16-bit resolution. Therefore, the new match value of the WDT counter is generated and updated on every WDT interrupt event to generate an interrupt after the present interrupt. The WDT interrupt flag is set inside the WDT interrupt service routine; it is checked in the main loop.

2. You can configure the values of the WDT interrupt interval and WDT interrupt priority using macros in main.c as shown in Figure 6 and update them.

   Figure 6. Accessing macros

   

Making current measurements for PSoC™ 4 MCU device

• CY8CKIT-149

  Measure the current by removing R53 resistor on the board and connect an ammeter at J3 header, between P4_VDD (J3.1) and VTARG (J3.2)

• CY8CKIT-145-40XX

  Measure the current by removing R22 resistor on the board and connect an ammeter at J3 header, between P4_VDD (J3.1) and VTARG (J3.2)

• CY8CKIT-045S

  Measure the current by removing the jumper shunt at J6 on the board and connect an ammeter between P4_VDD (J6.2) and VCC_3V3 (J6.3)

• CY8CKIT-041S-MAX

  Measure the current by removing the jumper shunt at J11 on the board and connect an ammeter between P4_VDD (J11.1) and VTARG (J11.2)

  Table 1. Current values of the suppoerted kits

  Kit	Low-power mode	Active mode
  CY8CKIT-149	1.9 mA	5.1 mA
  CY8CKIT-145-40XX	3.0 mA	6.4 mA
  CY8CKIT-045S	2.2 mA	4.5 mA
  CY8CKIT-041S-MAX	4.2 mA	4.2 mA

  Note: These are the average current numbers of the suported kits.

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

1. Open the Device Configurator from the Quick Panel.

2. Navigate to the System tab. Select the Power resource and set the VDDA value under Operating conditions.

3. By default, SWD pins are ACTIVE in all device power modes. Disablethe Debug mode to disable SWD pins and thereby reduce the power consumption as follows:

   Figure 7. Disable debug mode in the System tab of device configurator

   

Resources and settings

Resource	Alias/object	Purpose
SCB (UART)	CYBSP_UART	To send CAPSENSE™ slider data to serial terminal
CAPSENSE™	CYBSP_CSD	CAPSENSE™ driver to interact with CAPSENSE™ hardware and interface CAPSENSE™ sensors
Digital pin	CYBSP_USER_LED	To visually indicate the closeness of a hand to the proximity sensor

Related resources

Resources	Links
Application notes	AN79953 – Getting started with PSoC™ 4
Code examples	Using ModusToolbox™ software 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: CE239069 - PSoC™ 4: CAPSENSE™ low-power

Version	Description of change
1.0.0	New code example

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