README.md

# PSoC&trade; 4 MCU: CAPSENSE&trade; CSD button tuning

This code example demonstrates how to manually tune a self-capacitance (CSD)-based button widget in PSoC&trade; 4 devices using the CAPSENSE&trade; tuner. This document provides:

   1. A high-level overview of the CSD widget tuning flow

   2. An example to manually tune a CSD button widget

   3. Details on how to use the CAPSENSE&trade; tuner to monitor the CAPSENSE&trade; raw data and fine-tune the CSD button for optimum performance

[View this README on GitHub.](https://github.com/Infineon/mtb-example-psoc4-capsense-csd-button-tuning)

[Provide feedback on this code example.](https://cypress.co1.qualtrics.com/jfe/form/SV_1NTns53sK2yiljn?Q_EED=eyJVbmlxdWUgRG9jIElkIjoiQ0UyMzA5MjYiLCJTcGVjIE51bWJlciI6IjAwMi0zMDkyNiIsIkRvYyBUaXRsZSI6IlBTb0MmdHJhZGU7IDQgTUNVOiBDQVBTRU5TRSZ0cmFkZTsgQ1NEIGJ1dHRvbiB0dW5pbmciLCJyaWQiOiJibHBkIiwiRG9jIHZlcnNpb24iOiIzLjEuMCIsIkRvYyBMYW5ndWFnZSI6IkVuZ2xpc2giLCJEb2MgRGl2aXNpb24iOiJNQ0QiLCJEb2MgQlUiOiJJQ1ciLCJEb2MgRmFtaWx5IjoiUFNPQyJ9)

## Requirements

- [ModusToolbox&trade; software](https://www.infineon.com/modustoolbox) v3.1 or later (tested with v3.1)

   **Note:** This code example version requires ModusToolbox&trade; software version 3.1 or later and is not backward compatible with v2.4 or older versions.

- Board support package (BSP) minimum required version: 3.0.0
- Programming language: C
- Associated parts: [PSoC&trade; 4000S, PSoC&trade; 4100S, PSoC&trade; 4100S Plus and PSoC&trade; 4500S](https://www.infineon.com/cms/en/product/microcontroller/32-bit-psoc-arm-cortex-microcontroller/psoc-4-32-bit-arm-cortex-m0-mcu/)

## Supported toolchains (make variable 'TOOLCHAIN')

- GNU Arm&reg; embedded compiler v11.3.1 (`GCC_ARM`) - Default value of `TOOLCHAIN`
- Arm&reg; compiler v6.16 (`ARM`)
- IAR C/C++ compiler v9.30.1 (`IAR`)

## Supported kits (make variable 'TARGET')

- [PSoC&trade; 4100S Plus prototyping kit](https://www.infineon.com/CY8CKIT-149) (`CY8CKIT-149`) - Default value of `TARGET`
- [PSoC&trade; 4100S CAPSENSE&trade; pioneer kit](https://www.infineon.com/CY8CKIT-041-41XX) (`CY8CKIT-041-41XX`)
- [PSoC&trade; 4000S CAPSENSE&trade; prototyping kit](https://www.infineon.com/CY8CKIT-145-40XX) (`CY8CKIT-145-40XX`)
- [PSoC&trade; 4500S pioneer kit](https://www.infineon.com/CY8CKIT-045S) (`CY8CKIT-045S`)


## Hardware setup

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

**Note:** The PSoC&trade; 4 kits ship with KitProg2 installed. The ModusToolbox&trade; 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](https://github.com/Infineon/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 and open it using one of the following:

<details><summary><b>In Eclipse IDE for ModusToolbox&trade; software</b></summary>

1. Click the **New Application** link in the **Quick Panel** (or, use **File** > **New** > **ModusToolbox&trade; Application**). This launches the [Project Creator](https://www.infineon.com/ModusToolboxProjectCreator) 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](https://www.infineon.com/ModusToolboxLibraryManager) 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&trade; software user guide](https://www.infineon.com/MTBEclipseIDEUserGuide) (locally available at *{ModusToolbox&trade; software install directory}/docs_{version}/mt_ide_user_guide.pdf*).

</details>

<details><summary><b>In command-line interface (CLI)</b></summary>

ModusToolbox&trade; 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&trade; 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&trade; software installation instead of a standard Windows command-line application. This shell provides access to all ModusToolbox&trade; 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](https://github.com/Infineon?q=bsp-manifest&type=&language=&sort=) manifest | Required
`--app-id`   | Defined in the `<id>` field of the [CE](https://github.com/Infineon?q=ce-manifest&type=&language=&sort=) 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

<br />

The following example clones the "[CAPSENSE&trade; CSD button tuning](https://github.com/Infineon/mtb-example-psoc4-capsense-csd-button-tuning)" application with the desired name "CSDButtonTuning" configured for the *CY8CKIT-041-41XX* BSP into the specified working directory, *C:/mtb_projects*:

   ```
   project-creator-cli --board-id CY8CKIT-041-41XX --app-id mtb-example-psoc4-capsense-csd-button-tuning --user-app-name CSDButtonTuning --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&trade; software user guide](https://www.infineon.com/ModusToolboxUserGuide) (locally available at *{ModusToolbox&trade; software install directory}/docs_{version}/mtb_user_guide.pdf*).

To work with a different supported kit later, use the [Library Manager](https://www.infineon.com/ModusToolboxLibraryManager) to choose the BSP for the supported kit. You can invoke the Library Manager GUI tool from the terminal using `make library-manager` 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

<br />

Following example adds the CY8CKIT-149 BSP to the already created application and makes it the active BSP for the app:

   ```
   ~/ModusToolbox/tools_3.1/library-manager/library-manager-cli --project "C:/mtb_projects/CSDButtonTuning" --add-bsp-name CY8CKIT-149 --add-bsp-version "latest-v3.X" --add-bsp-location "local"

   ~/ModusToolbox/tools_3.1/library-manager/library-manager-cli --project "C:/mtb_projects/CSDButtonTuning" --set-active-bsp APP_CY8CKIT-149
   ```

</details>

<details><summary><b>In third-party IDEs</b></summary>

Use one of the following options:

- **Use the standalone [Project Creator](https://www.infineon.com/ModusToolboxProjectCreator) tool:**

   1. Launch Project Creator from the Windows Start menu or from *{ModusToolbox&trade; 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.

<br />

- **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&trade; software user guide](https://www.infineon.com/ModusToolboxUserGuide) (locally available at *{ModusToolbox&trade; software install directory}/docs_{version}/mtb_user_guide.pdf*).

</details>


## Tuning flow summary

Figure 1 gives a high-level summary on how to tune a CSD-based CAPSENSE&trade; button in PSoC&trade; 4 devices. See the “Manual tuning” section in [AN85951 – PSoC&trade; 4 and PSoC&trade; 6 MCU CAPSENSE&trade; design guide](https://www.infineon.com/AN85951) for information on the hardware and threshold parameters that determines the CAPSENSE&trade; touch performance.

**Figure 1. High-level overview of CSD button tuning**

<img src="images/tuning-flowchart.png" alt="" width="400"/>


## Operation

This process involves the following stages:

- [Stage 1: Set initial hardware parameters](#stage-1-set-initial-hardware-parameters)

- [Stage 2: Measure SNR](#stage-2-measure-snr)

- [Stage 3: Modify hardware parameters or adjust filter settings](#stage-3-modify-hardware-parameters-or-adjust-filter-settings)

- [Stage 4: Set the software threshold parameters using CAPSENSE&trade; tuner](#stage-4-set-the-software-threshold-parameters-using-capsense-tuner)


### Stage 1: Set initial hardware parameters


Connect the board to your PC using the provided micro USB cable through the KitProg3 USB connector, and launch the CAPSENSE&trade; configurator.

See the "Launch the CAPSENSE&trade; configurator" section from the [ModusToolbox&trade; CAPSENSE&trade; configurator guide](https://www.infineon.com/ModusToolboxCapSenseConfig).

In the **Basics** tab, you will find a single widget ‘Button0’ configured as a CSD button and the CSD Tuning method selected as **Manual tuning**.

**Figure 2. CAPSENSE&trade; configurator - General settings**

<img src="images/basic-csd-settings.png" alt=""/>


#### 1. Set the initial general parameters.

   1. Navigate to the **Advanced** tab, and then select the **General Settings** sub-tab. Leave all the filter parameters at their default settings. Filters will be enabled depending on the SNR and system time requirements.

   2. Select **Enable self-test library** to perform sensor capacitance measurement using the CAPSENSE&trade; middleware APIs in the firmware. See [Step 3. Set the sense clock divider and sense clock source](#3-set-the-sense-clock-divider-and-sense-clock-source).

      **Figure 3. CAPSENSE&trade; configurator - General settings**

      <img src="images/advanced-general-settings.png" alt=""/>


#### 2. Set the initial hardware parameters.

   1. Select the **Advanced** tab and then select the **CSD Settings** sub-tab.

   2. Configure the parameters as Table 1 and Figure 4 show.

      **Table 1. Advanced tab - CSD settings**

      | Parameter | Value | Remarks |
      | --- | --- | --- |
      | Modulator clock divider | 1 (To obtain the maximum allowed by the selected device) | A higher modulator clock frequency reduces flat spots, and increases the  measurement accuracy and sensitivity. It also reduces the sensor scan time, which results in lower power consumption. Therefore, it is recommended to select the highest possible available modulator clock frequency. |
      | Inactive sensor connection | Ground (default) | Inactive sensors are connected to ground to provide good shielding from noise sources. Use the inactive sensor connection as shield for liquid-tolerant designs if your design contains a proximity sensor or if the adjacent sensors are being used to reduce Cp of sensors.
      | IDAC sensing configuration | IDAC sourcing (default) | Choose IDAC sourcing mode because it is more susceptible to VDD noise compared to IDAC sinking mode. However, if you have clean/noise-free VDD, you may choose IDAC sinking mode for a higher SNR.
      | Enable IDAC auto-calibration | Checked | Enabling auto-calibration allows the device to automatically choose the optimal IDAC value such that it calibrates the raw count of the sensor to 85 percent of its maximum value.
      | Enable compensation IDAC | Checked | Enabling the compensation IDAC selects the dual-IDAC mode operation of the CSD. Dual-IDAC mode gives higher signal values compared to single-IDAC mode for fixed values of CAPSENSE&trade; parameters.
      | Enable shield electrode | Unchecked (default) |Enable shield if your design requires a large proximity sensing distance, liquid tolerance, or if the shield is being used to reduce the Cp of sensors. Before enabling this option, ensure that the PCB has a shield electrode or hatched pattern connected to the device pin.

      <br />

      **Figure 4. CAPSENSE&trade; Configurator - Advanced CSD Settings**

      <img src="images/advanced-csd-settings.png" alt=""/>

      **Note:** You can change the modulator clock frequency to **48 MHz** only after changing the IMO clock frequency to 48 MHz. To do this, navigate to the **System** tab in the **Device Configurator** tool, select **System Clocks** > **Input** > **IMO**. Select **48** from the **Frequency(MHz)** dropdown list.


#### 3. Set the sense clock divider and sense clock source.

   1. Navigate to the **Advanced** tab, and then select the **Widget Details** sub tab.

   2. Set the sense clock divider and sense clock source per the following guidelines:

      - Sense clock divider

         In the CAPSENSE&trade; configurator, set the sense clock frequency in terms of the sense clock divider as shown in Equation 1:

         **Equation 1. Sense clock divider**

         <img src="images/scd-equation.png" alt="" width="250"/>

         Set the maximum possible sense clock frequency which will completely charge and discharge the sensor parasitic capacitance. Verify the charging and discharging of the sensor waveform with an oscilloscope by probing the sensor using an active probe.

         Use Equation 2 to compute the maximum sense clock frequency using the Cp of the sensor and the total series resistance R<sub>Series</sub>. Note that the CAPSENSE&trade; configurator allows a maximum sense clock frequency of 6 MHz; therefore, you cannot set it above 6 MHz.

         **Equation 2. Maximum sense clock frequency**

         <img src="images/fsw-equation.png" alt="" width="250"/>

         Cp is the parasitic capacitance of the sensor electrode.

         R<sub>SeriesTotal</sub> is the total series resistance, which includes the 500 ohm pin internal resistance, the external series resistance (in CY8CKIT-149, it is 2 kilo-ohm), and the trace resistance. Include the trace resistance if a high-resistive material such as ITO, or conductive ink is used. The external resistor is connected between the sensor pad and the device pin to reduce the radiated emission and for ESD protection.

         Use one of the following options to determine the Cp of the sensor:

         - [Option 1: Using the BIST API in CAPSENSE&trade; middleware](#option-1-using-the-bist-api-in-capsense-middleware)

         - [Option 2: Using an LCR meter](#option-2-using-an-lcr-meter)


         #### **Option 1: Using the BIST API in CAPSENSE&trade; middleware**

         While using this procedure, ensure that you have enabled the **Enable self-test library** option in the CAPSENSE&trade; configurator. After you obtained the Cp value, you can disable this option.

         1. Estimate the Cp of the sensor electrode using the `Cy_CapSense_MeasureCapacitanceSensor()` function in firmware. The measured capacitance value is in femtofarad (fF).

         2. Program the board in Debug mode.

            In the IDE, use the **\<Application Name> Debug (KitProg3)** configuration in the **Quick Panel**.

            For more details, see the "Program and debug" section in the Eclipse IDE for ModusToolbox&trade; user guide: *{ModusToolbox&trade; install directory}/ide_{version}/docs/mt_ide_user_guide.pdf*.

         3. Place a breakpoint after the capacitance measurement.

         4. In the **Expressions** window, add the Cp measurement variable `sensor_cp`.

            The status of the measurement can also be read through the return value of the function in the **Expressions** window.

         5. Click the **Resume** button (green arrow) to reach the breakpoint.

            **Note:** The function return value reads `CY_CAPSENSE_BIST_SUCCESS_E`; the measurement variables provide the capacitance value of the sensor elements in femtofarad as shown in Figure 5.

         6. Click **Terminate** button (red box) to exit Debug mode.

            **Figure 5. Cp measurement using BIST**

            <img src="images/debug-cp-measure.png" alt=""/>


         #### **Option 2: Using an LCR meter**

         Measure the Cp of the sensor electrode of the button using an LCR meter. The Cp should be measured between the sensor electrode (sensor pin) and the device ground.

         **Table 2. Sense clock divider settings in CAPSENSE&trade; configurator**

         |Development kit | Cp of sensor electrode (pF)| R<sub>SeriesTotal</sub> (ohm) |  Maximum sense clock frequency (kHz)| Sense clock divider setting in configurator|
         | --- | --- | --- | --- | --- |
         |CY8CKIT-149 (Pin P4.5) | 10 | 2.5K | 4000 | 12 |
         |CY8CKIT-145 (Pin P1.5) | 9 | 1060 | 6000 | 8 |
         |CY8CKIT-041-41xx (Pin P0.1) | 44 | 1060 | 2144 | 23|
         |CY8CKIT-045S (Pin P4.4) | 13 | 2.5K | 1740 | 16 |

         <br />

      - Sense clock source

         Select **Auto** as the sense clock source to automatically choose the correct spread spectrum clock (SSC) or PRS clock as the sense clock source to deal with EMI/EMC or flat spots issues.

   3. Ensure that the following conditions are also satisfied when selecting the sense clock frequency and sense clock source:

      - The auto-calibrated IDAC value should lie in the mid-range (for example, 18-110) for the selected F<sub>sw</sub>. If the auto-calibrated IDAC value lies out of the recommended range, ensure that F<sub>sw</sub> is tuned such that IDAC falls within the recommended range. See [Ensure that the auto-calibrated IDAC is within the recommended range](#2-ensure-that-the-auto-calibrated-idac-is-within-the-recommended-range).

      - If you are explicitly using the PRS or SSCx clock source, ensure that you select the sense clock frequency that meets the conditions mentioned in the [ModusToolbox&trade; software CAPSENSE&trade; configurator guide](https://www.infineon.com/ModusToolboxCapSenseConfig).


#### 4. Set the initial scan resolution.

   Set the scan resolution to an initial low value of 10. This will be modified in [Stage 3: Modify hardware parameters or adjust filter settings](#stage-3-modify-hardware-parameters-or-adjust-filter-settings) based on the signal-to-noise ratio (SNR) and system timing requirements.

   **Figure 6. Advanced tab - Widget Details**

   <img src="images/advanced-widget-settings.png" alt=""/>

#### 5. Program the board using one of the following:

   <details><summary><b>Using Eclipse IDE for ModusToolbox&trade; software</b></summary>

      1. Select the application project in the Project Explorer.

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

   <details><summary><b>Using CLI</b></summary>

     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
      ```
   </details>


### Stage 2: Measure SNR


#### 1. Set up the CAPSENSE&trade; tuner to view the sensor data.

   1. Launch the **CAPSENSE&trade; tuner**.

      See the "Launch the CAPSENSE&trade; tuner" section from the [ModusToolbox&trade; software CAPSENSE&trade; tuner guide](https://www.infineon.com/ModusToolboxCapSenseTuner).

   2. Go to **Tools** > **Tuner Communication Setup** and set the parameters as Figure 7 shows. Click **OK**.

      **Figure 7. Tuner Communication Setup**

      <img src="images/tuner-comm-setup.png" alt="" width="600"/>

   3. Click **Connect**.

      **Figure 8. CAPSENSE&trade; tuner window**

      <img src="images/tuner-connect.png" alt="" width="400"/>

   4. Click **Start**.

      **Figure 9. CAPSENSE&trade; tuner start**

      <img src="images/tuner-start.png" alt="" width="400"/>

      The **Widget/Sensor Parameters** tab gets updated with the parameters configured in the **CAPSENSE&trade; Configurator** window.

      **Figure 10. CAPSENSE&trade; tuner window**

      <img src="images/tuner-widget-settings.png" alt=""/>

   5. Select the **Button0** check box and **Synchronized** under **Read mode**, and then navigate to **Graph View** as Figure 11 shows.

      The **Graph View** shows the raw counts and baseline for **Button0** in the **Sensor data** window. Ensure that the **Raw counts** and **Baseline** checkboxes are selected to view the sensor data.

      **Figure 11. CAPSENSE&trade; tuner graph view**

      <img src="images/tuner-graph-view.png" alt=""/>

      **Note:** At this point, when the configured button is touched, you may or may not notice the touch signal in the **Sensor Signal** graph. The sensor may false-trigger which can be seen in the touch status going from 0 to 1 in the **Status** window.


#### 2. Ensure that the auto-calibrated IDAC is within the recommended range.

   As discussed in previous section, the sense clock frequency will be tuned to bring IDAC code to the recommended range in this step. Click **Button0** in the **Widget Explorer** to view the IDAC value in the sensor parameters window as shown in Figure 12. If the IDAC value is within the range (18 to 110), this step is not required.

   Increasing the sense clock divider will decrease the IDAC value for a fixed IDAC gain and calibration percent and vice versa.

   **Figure 12. IDAC value**

   <img src="images/tuner-idac-setting.png" alt="" width="400"/>


#### 3. Fine-tune the sense clock frequency to bring the IDAC within range.

   1. Click **Button0** in the **Widget Explorer**.

   2. Increase or decrease the sense clock divider in the **Widget hardware parameters** window.

   3. Click the **To Device** button to apply the changes to the device as shown in Figure 13.

      **Figure 13. Apply changes to the device**

      <img src="images/tuner-apply-to-device.png" alt=""/>

   4. Observe the Modulator IDAC and Compensation IDAC value in the **Sensor Parameters** section of the **Widget/Sensor Parameters** window.

   5. Repeat steps 1 to 4 until you obtain the IDAC value in the range of 18 to 110.

      **Note:** As Figure 13 shows, IDAC values are already in the recommended range. Therefore, you can leave the sense clock divider to the value as shown in Table 2.


#### 4. Measure SNR.

   1. Switch to the **SNR Measurement** tab, select the **Button0** sensor, and then click **Acquire Noise** as Figure 14 shows.

      **Figure 14. CAPSENSE&trade; tuner - SNR Measurement: Acquire Noise**

      <img src="images/tuner-acquire-noise.png" alt=""/>

   2. Once the noise is acquired, touch the button on the kit, and then click **Acquire Signal**. Ensure that the finger remains on the button as long as the signal acquisition is in progress.

      The calculated SNR on this button is displayed, as Figure 15 shows. Based on your end-system design, test with a finger that matches the size of your normal use case. Typically, finger size targets are ~8 to 9 mm.

      **Figure 15. CAPSENSE&trade; tuner - SNR Measurement: Acquire Signal**

      <img src="images/tuner-acquire-signal.png" alt=""/>


### Stage 3. Modify hardware parameters or adjust filter settings


Skip this stage if the following conditions are met:

- Measured SNR from the previous step is greater than 5:1
- Signal count is greater than 50
- Response time requirement are met

If the SNR is less than 5:1, do the following to increase the touch performance. The main parameters that influence SNR are **scan resolution** and **filters**.

It is best to find a balance between the resolution and filters to achieve proper overall tuning. If your system is very noisy (counts >20), you may want to prioritize adding a filter. On the other hand, if your system is relatively noise-free (counts <10), you should focus on resolution, as this will increase the sensitivity and signal of your system.


#### **Scan resolution**

Scan resolution can be increased to increase the signal at a disproportionate rate to noise to improve the overall SNR. Increasing the resolution adds to the overall hardware scan time based on Equation 3.

**Equation 3. Scan time**

<img src="images/scantime-equation.png" alt="" width="200"/>

Do the following to update the scan resolution:

1. Update the scan resolution (N) directly in the **Widget/Sensor Parameters** tab of the CAPSENSE&trade; tuner.

2. Increase the scan resolution by one and repeat steps in [Measure SNR](#4-measure-snr) until the minimum SNR of 5:1 and at least a signal count greater than 50 are achieved.


#### **Firmware filters**

Firmware filters help to reduce noise without increasing the signal. Based on your noise type, you can enable a filter to improve SNR. Each filter will add additional processing time as well as memory use. If your system is very noisy (counts > 20), add a filter.

1. Open CAPSENSE&trade; configurator and select the appropriate filter as shown in Figure 16.

2. Reprogram the device to update filter settings.

   **Note:** Add the filter based on the type of noise in your measurements. See [ModusToolbox&trade; software CAPSENSE&trade; configurator guide](https://www.infineon.com/ModusToolboxCapSenseConfig) for details.

   **Figure 16. Filter settings in CAPSENSE&trade; configurator**

   <img src="images/advanced-filter-settings.png" alt=""/>

   **Note:** The current example has approximately 10:1 SNR; therefore, filters are not enabled.

   After setting the scan resolution and filter settings, check the total scan time based on Equation 3 to determine whether system requirements are met. This timing will impact the response time and is a crucial factor in the overall power consumption of the device in CAPSENSE&trade; applications.

   If the total sensor scan time meets your requirements, go to the next step.

   If not, adjust the tuning to speed up the scan time (decrease the scan resolution or increasing the F<sub>MOD</sub>). If the SNR is greater than 10 on any sensor, lower the scan resolution or remove filters to decrease the scan time, but keep the SNR greater than 5:1. It is best to find a balance between the scan resolution and filters to achieve proper overall tuning.

3. Use Table 3 to set the hardware tuning parameters to achieve 5:1 SNR.

   **Table 3. Final hardware tuning parameters to achieve 5:1 SNR (with firmware filters disabled)**

   |Development kit | Sense clock divider setting in configurator| Scan resolution |
   | --- | --- | --- |
   |CY8CKIT-149| 12| 11 |
   |CY8CKIT-145| 8| 9 |
   |CY8CKIT-041-41xx| 23| 11 |
   | CY8CKIT-045S | 16 | 10 |

   <br />

### Stage 4: Set the software threshold parameters using CAPSENSE&trade; tuner

After you have confirmed that your design meets the timing parameters, and the SNR is greater than 5:1, set your threshold parameters as follows:

1. Switch to the **Graph View** tab and select **Button0** (CSD).

2. Touch the sensor and monitor the touch signal in the **Sensor Signal** graph.

   The **Sensor Signal** graph should show the signal as Figure 17 shows.

   Ensure that you observe the difference count (that is, the signal output) in the **Graph View** tab in Figure 17, not the raw count output for setting these thresholds. 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. Also ensure to ground the metal finger.

   **Figure 17. Sensor signal when the sensor is touched**

   <img src="images/tuner-diff-signal.png" alt=""/>

3. When the signal is measured, set the thresholds according to the following recommendations:

   - Finger threshold = 80 percent of signal
   - Noise threshold = 40 percent of signal
   - Negative noise threshold = 40 percent of signal
   - Hysteresis = 10 percent of signal
   - Debounce = 3

4. Set the threshold parameters in the **Widget/Sensor Parameters** section of the CAPSENSE&trade; tuner, as Figure 18 shows:

   **Figure 18. Widget threshold parameters**

   <img src="images/tuner-threshold-settings.png" alt="" width="300"/>

   See Table 4 to set the threshold parameters in the CAPSENSE&trade; tuner for different development kits.

   **Table 4. Threshold parameters for different development kits**

   | Development kit | Difference counts | Finger threshold | Noise threshold | Negative noise threshold | Hysteresis | Low baseline reset | Debounce |
   | --- | --- | --- | --- | --- | --- | --- | --- |
   |CY8CKIT-149| 80 | 64 | 32 | 32 | 8 | 30 | 3 |
   |CY8CKIT-145-40XX| 80 | 64 | 32 | 32 | 8 | 30 | 3 |
   |CY8CKIT-041-41XX| 60 | 48 | 24 | 24 | 6 | 30 | 3 |
   | CY8CKIT-045S   | 80 | 64 | 32 | 32 | 8 | 30 | 3 |

   <br />

5. Apply the settings to the device and to the project by clicking on the **To Device** icon and then the **To Project** icon as Figure 19 shows, and close the tuner.

   **Figure 19. Apply settings to project setting**

   <img src="images/tuner-apply-settings.png" alt=""/>

   If your sensor is tuned correctly, you will observe the touch status go from 0 to 1 in the **Status** sub-window of the **Graph View** tab as Figure 20 shows. The successful tuning of the button is also indicated by a user LED in the prototyping kit; the LED is turned ON when the finger touches the button and turned OFF when the finger is removed from the button.

   **Figure 20. Sensor status in CAPSENSE&trade; tuner**

   <img src="images/tuner-status.png" alt=""/>

6. Launch **CAPSENSE&trade; Configurator**. You should now see all the changes that you made in the CAPSENSE&trade; tuner reflected in the **CAPSENSE&trade; Configurator**.


## 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&trade; software user guide](https://www.infineon.com/MTBEclipseIDEUserGuide).


## Design and implementation

The project contains a single button widget configured in CSD sensing mode. See the "CAPSENSE&trade; CSD sensing method" section in the [AN85951 – PSoC&trade; 4 and PSoC&trade; 6 MCU CAPSENSE&trade; design guide](https://www.infineon.com/an85951)  for details on CAPSENSE&trade; CSD sensing mode. See the [Operation](#operation) section for step-by-step instructions to configure the other settings of the CAPSENSE&trade; configurator.

The project uses the [CAPSENSE&trade; middleware](https://github.com/Infineon/capsense) (see ModusToolbox&trade; software user guide for more details on selecting a middleware). See [AN85951 – PSoC&trade; 4 and PSoC&trade; 6 MCU CAPSENSE&trade; design guide](https://www.infineon.con/AN85951) for more details on CAPSENSE&trade; features and usage.

The [ModusToolbox&trade; software](https://www.infineon.com/ModusToolbox) provides a GUI-based tuner application for debugging and tuning the CAPSENSE&trade; system. The CAPSENSE&trade; tuner application works with the EZI2C and UART communication interfaces. This project has an SCB block configured in EZI2C mode to establish communication with the on-board KitProg, which in turn enables reading the CAPSENSE&trade; raw data by the CAPSENSE&trade; tuner. See [EZI2C - Peripheral settings](#resources-and-settings).

The CAPSENSE&trade; data structure that contains the CAPSENSE&trade; raw data is exposed to the CAPSENSE&trade; tuner by setting up the I2C communication data buffer with the CAPSENSE&trade; data structure. This enables the tuner to access the CAPSENSE&trade; raw data for tuning and debugging.

The successful tuning of the button is indicated by a user LED in the prototyping kit; the LED is turned ON when the finger touches the button and turned OFF when the finger is removed from the button. Figure 21 shows the firmware flow for this code example.

**Figure 21. Firmware design**

<img src="images/firmware-flowchart.png" alt=""/>


### Resources and settings

**Figure 22. EZI2C Settings**

<img src="images/ezi2c-config.png" alt=""/>

**Table 5. Application resources**

| Resource  |  Alias/object     |    Purpose     |
| :------- | :------------    | :------------ |
| SCB (I2C) (PDL) | CYBSP_EZI2C          | EZI2C slave driver to communicate with the CAPSENSE&trade; tuner |
| CAPSENSE&trade; | CYBSP_CSD | CAPSENSE&trade; driver to interact with the CSD hardware and interface CAPSENSE&trade; sensors |
| Digital pin | CYBSP_LED_BTN1 | To show the button operation|

<br />

## Related resources

Resources  | Links
-----------|----------------------------------
Application notes  | [AN79953](https://www.infineon.com/AN79953) – Getting started with PSoC&trade; 4 <br /> [AN85951](https://www.infineon.com/AN85951) – PSoC&trade; 4 and PSoC&trade; 6 MCU CAPSENSE&trade; design guide
Code examples  | [Using ModusToolbox&trade; software](https://github.com/Infineon/Code-Examples-for-ModusToolbox-Software) on GitHub <br /> [Using PSoC&trade; Creator](https://www.infineon.com/cms/en/design-support/software/code-examples/psoc-3-4-5-code-examples-for-psoc-creator/)
Device documentation | [PSoC&trade; 4 datasheets](https://www.infineon.com/cms/en/search.html#!view=downloads&term=psoc4&doc_group=Data%20Sheet) <br />[PSoC&trade; 4 technical reference manuals](https://www.infineon.com/cms/en/search.html#!view=downloads&term=psoc4&doc_group=Additional%20Technical%20Information)
Development kits | Select your kits from the [evaluation board finder](https://www.infineon.com/cms/en/design-support/finder-selection-tools/product-finder/evaluation-board)
Libraries on GitHub | [mtb-pdl-cat2](https://github.com/Infineon/mtb-pdl-cat2) – PSoC&trade; 4 peripheral driver library (PDL)<br /> [mtb-hal-cat2](https://github.com/Infineon/mtb-hal-cat2) – Hardware abstraction layer (HAL) library
Middleware on GitHub | [capsense](https://github.com/Infineon/capsense) – CAPSENSE&trade; library and documents <br />
Tools  | [ModusToolbox&trade; software](https://www.infineon.com/modustoolbox) – ModusToolbox&trade; 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&trade; Wi-Fi and Bluetooth® connectivity devices. <br /> [PSoC&trade; Creator](https://www.infineon.com/cms/en/design-support/tools/sdk/psoc-software/psoc-creator/) – IDE for PSoC&trade; and FM0+ MCU development

<br />

## 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: *CE230926* - *PSoC&trade; 4 MCU: CAPSENSE&trade; CSD button tuning*

| Version | Description of change |
| ------- | --------------------- |
| 1.0.0   | New code example      |
| 2.0.0   | Major update to support ModusToolbox&trade; software v2.4 and updated to use CAPSENSE™ MW 3.X <br /> Added support for CY8CKIT-045S kit <br />  This version is not backward compatible with ModusToolbox&trade; software v2.3|
| 3.0.0   | Major update to support ModusToolbox&trade;  v3.0. This version is not backward compatible with previous versions of ModusToolbox&trade;  |
| 3.1.0   | Update to support ModusToolbox&trade; v3.1 and CAPSENSE&trade; middleware v4.X  |
<br />

---------------------------------------------------------

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