This code example demonstrates an implementation of a low-power proximity sensing application for maximum proximity sensing at the longest distance to detect a target (a hand). It includes recommended power states and transitions, adjustments for tuning parameters, and the method of tuning. This example uses a proximity widget in multi-sense CAPSENSE™ low-power (MSCLP - 5th-generation low-power CAPSENSE™) to demonstrate different considerations for implementing a low-power design.
This document also explains how to manually tune the low-power widget for optimum performance and the longest distance according to parameters such as power consumption and response time using the CSD-RM sensing technique and CAPSENSE™ Tuner.
Provide feedback on this code example.
- ModusToolbox™ v3.2 or later (tested with v3.2)
- Board support package (BSP) minimum required version: 3.2.0
- Programming language: C
- Associated parts: PSoC™ 4000T
- GNU Arm® Embedded Compiler v11.3.1 (
GCC_ARM) – Default value ofTOOLCHAIN - Arm® Compiler v6.16 (
ARM) - IAR C/C++ Compiler v9.30.1 (
IAR)
- PSoC™ 4000T CAPSENSE™ Prototyping Kit (
CY8CPROTO-040T) – Default value ofTARGET
This example uses the board's default configuration. See the kit user guide to ensure that the board is configured correctly to use VDD at 5 V.
See the ModusToolbox™ tools package installation guide for information about installing and configuring the tools package.
This example requires no additional software or tools.
The ModusToolbox™ tools package provides the Project Creator as both a GUI tool and a command line tool.
Use Project Creator GUI
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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).
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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.
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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-low-power-csd-proximity" application with the desired name "MSCLP_Low_Power_Proximity" configured for the CY8CPROTO-040T BSP into the specified working directory, C:/mtb_projects:
project-creator-cli --board-id CY8CPROTO-040T --app-id mtb-example-psoc4-msclp-low-power-csd-proximity --user-app-name MSCLP_Low_Power_Proximity --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).
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).
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Connect the board to your PC using the provided Micro-B USB cable through the KitProg3 USB connector as shown in Figure 1.
Figure 1. Connecting the CY8CPROTO-040T kit with the PC
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Program the board using one of the following:
Using Eclipse IDE
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Select the application project in the Project Explorer.
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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 programcommand 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 -
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After programming, the application starts automatically.
Note: After programming, you see the following error message if debug mode is disabled. This can be ignored or enabling the debug mode will solve this error.
"Error: Error connecting Dp: Cannot read IDR" -
To test the application, hover a hand on top of the CAPSENSE™ proximity sensor and notice that LED2 turn ON and turn OFF when the hand is moved away. The LED2 brightness changes based on hand distance. In this case, the maximum distance the proximity sensor can sense an object is 40 mm.
The sensor can also detect a touch. When you touch the sensor (outer loop) the LED3 turn ON and turn OFF when you remove the touch.
Note that the proximity sensor detects objects from all directions. Implementing directional proximity sensing in an end system presents a significant challenge due to its dependence on various factors, including the overall enclosure design, hardware components, and PCB layout. To achieve directional sensitivity in proximity sensors, position a ground plane at the bottom to reduce sensitivity from below. Because the ground plane can decrease sensitivity, it must be placed with some separation from the shield below the proximity sensor. The optimal distance varies based on different system factors and necessitates testing on the actual system to determine the best distance.
Figure 2. LED2 turn ON after hovering the hand on top of the sensor
Table 1. LED indications for proximity and touch detection
Scenario LED Status Hand in proximity LED2 ON (brightness changes based on hand distance) Touch LED3 ON
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Open CAPSENSE™ Tuner from the BSP Configurators section in the IDE Quick Panel.
You can also run the CAPSENSE™ Tuner application in standalone mode 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 present in the {Application root directory}/bsps/TARGET_APP_<BSP-NAME>/COMPONENT_BSP_DESIGN_MODUS/ 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.
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Ensure the kit is in CMSIS-DAP bulk mode (KitProg3 status LED is ON and not blinking). See Firmware-loader to learn how to update the firmware and switch modes in KitProg3.
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In the tuner application, click on the Tuner Communication Setup icon or select Tools > Tuner Communication Setup. In the window, select I2C under KitProg3 and configure as follows:
- I2C address: 8
- Sub-address: 2-Bytes
- Speed (kHz): 400
These are the same values set in the EZI2C resource.
Figure 3. Tuner Communication Setup parameters
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Click Connect or select Communication > Connect to establish a connection.
Figure 4. Establish connection
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Click Start or select Communication > Start to start data streaming from the device.
Figure 5. 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.
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Set the Read mode to Synchronized mode. Navigate to the Widget View tab and observe that the Proximity0 widget is highlighted in blue color when you touch it.
Figure 6. Widget view of the CAPSENSE™ Tuner
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Go to the Graph View tab to view the raw count, baseline, difference count, and status for each sensor. Observe that the low-power widget sensor's (LowPower0_Sns0) raw count is plotted after the device completes a full-frame scan (or detects a touch) in WOT mode and moves to Active/ALR mode.
Figure 7. Graph view of the CAPSENSE™ Tuner
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See the Widget/Sensor parameters section in the CAPSENSE™ Tuner window as shown in Figure 7.
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Switch to the SNR Measurement tab for measuring the SNR and verify that the SNR is above 5:1 and the signal count is above 50; select the Proximity0 and Proximity0_Sns0 sensors, and then click Acquire Noise as shown in Figure 8.
Figure 8. CAPSENSE™ Tuner - SNR measurement: Acquire noise
Note: Because the scan refresh rate is lower in ALR mode, it takes more time to acquire noise. Touch the CAPSENSE™ proximity loop once before clicking Acquire Noise to transition the device to ACTIVE mode to complete the measurement faster.
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After noise is acquired, bring your hand near the proximity loop at a distance of around 40 mm above it and then click Acquire Signal. Ensure that the hand remains above the proximity loop as long as the signal acquisition is in progress. Observe that the SNR is above 5:1 and the signal count is above 50. If not, repeat signal acquisition by lowering the hand, and therefore, getting a higher signal.
The maximum distance the proximity loop can sense is when the SNR is greater than 5:1 for a particular configuration. Tuning procedure section explains how changing the configuration affects the distance and SNR.
The calculated SNR on this proximity widget is displayed, as Figure 9 shows.
Figure 9. CAPSENSE™ Tuner - SNR measurement: Acquire signal
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To tune the low-power widget, see the Tuning flow section of the code example PSoC™ 4: MSCLP low-power CSD button.
Note : Refer to the PSoC™ 4: MSCLP low-power CSD button to observe the power state transitions, indicated by changing the blinking rate of a LED. The Code Example also explains the scan time and process time measurements.
Follow the instructions in the Measure current at different power modes section of the code example PSoC™ 4: MSCLP low-power CSD button to measure the current consumption.
CY8CPROTO-040T 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 the Set up the VDDA supply voltage and debug mode in Device Configurator section.
This application functionalities are optimally tuned for 5 V. However, you can observe the basic functionalities working across other voltages.
It is recommended to tune the application with the preferred voltages for better performance.
Create custom BSP for your board
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Create a custom BSP for your board with any device by following the steps given in ModusToolbox™ BSP Assistant user guide. This code example is created for the CY8C4046LQI-T452 device.
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Open the design.modus file from the {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 be started from scratch as follows:
The following steps explain the tuning procedure for the proximity loop and the low-power widget.
Note: See the "Manual Tuning" section in the AN92239 - Proximity sensing with CAPSENSE™ to learn about the considerations for selecting each parameter values. In addition, see the "Low-power widget parameters" section in the AN234231 - Achieving lowest-power capacitive sensing with PSoC™ 4000T to learn about the considerations for parameter values specific to low-power widgets.
The tuning flow of the proximity widget is shown in Figure 10.
Figure 10. Proximity widget tuning flow
To tune the low-power widget, see the Tuning flow section of the code example PSoC™ 4: MSCLP low-power CSD button.
Do the following to tune the proximity widget:
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Connect the board to the PC using the provided USB cable through the KitProg3 USB connector.
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Launch the Device Configurator tool.
You can launch the Device Configurator in Eclipse IDE for ModusToolbox™ from the Tools section in the IDE Quick Panel or in standalone mode from {ModusToolbox™ install directory}/ModusToolbox/tools_{version}/device-configurator/device-configurator. In this case, after opening the application, select File > Open and open the design.modus file of the respective application located in the {Application root directory}/bsps/TARGET_APP_<BSP-NAME>/COMPONENT_BSP_DESIGN_MODUS folder.
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Enable CAPSENSE™ channel in Device Configurator as shown in Figure 11.
Figure 11. Enable CAPSENSE™ in Device Configurator
Save the changes and close the window.
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Launch the CAPSENSE™ Configurator tool.
You can launch the CAPSENSE™ Configurator tool in Eclipse IDE for ModusToolbox™ from the CAPSENSE™ peripheral setting in the Device Configurator or directly from the Tools section in the IDE Quick Panel.
You can also launch it in standalone mode from {ModusToolbox™ install directory}/ModusToolbox™/tools_{version}/capsense-configurator/capsense-configurator. In this case, after opening the application, select File > Open and open the design.cycapsense file of the respective application, which is present in the {Application root directory}/bsps/TARGET_APP_<BSP-NAME>/COMPONENT_BSP_DESIGN_MODUS folder.
See the ModusToolbox™ CAPSENSE™ Configurator tool guide for step-by-step instructions on how to configure and launch CAPSENSE™ in ModusToolbox™.
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In the Basic tab, add a proximity widget Proximity0 and a low-power widget LowPower0. Set their sensing mode as CSD RM (self-cap) and set the CSD tuning mode as Manual tuning.
Figure 12. CAPSENSE™ Configurator - Basic tab
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Do the following in the General tab under the Advanced tab:
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Select CAPSENSE™ IMO Clock frequency as 46 MHz.
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Set the Modulator clock divider to 1 to obtain the optimum modulator clock frequency.
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Set the Number of init sub-conversions based on the hint shown when you hover over the edit box. Retain the default value (which will be set in Stage 2: Set sense clock frequency).
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Use Wake-On-Touch settings to set the refresh rate and frame timeout while in the lowest power mode (Wake-on-Touch mode).
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Set Wake-on-Touch scan interval (ms) based on the required low-power state scan refresh rate. For example, to get a 16-Hz refresh rate, set the value to 62500.
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Set the Number of frames in Wake-on-Touch as the maximum number of frames to be scanned in WoT mode if there is no touch detected. This determines the maximum time the device will be kept in the lowest-power mode if there is no user activity. The maximum time can be calculated by multiplying this parameter with the Wake-on-Touch scan interval (µs) value.
For example, to get 10 seconds as the maximum time in WoT mode, set Number of frames in Wake-on-Touch to 160 for the scan interval set as 62500 µs.
Note: For tuning low-power widgets, Number of frames in Wake-on-Touch must be less than the Maximum number of raw counts values in SRAM based on the number of sensors in WoT mode as follows:
Table 2. Maximum number of raw counts values in SRAM
Number of low power widgets Maximum number of raw counts in SRAM 1 245 2 117 3 74 4 53 5 40 6 31 7 25 8 21
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Retain the default settings for all regular and low-power widget filters. You can enable or update the filters later depending on the signal-to-noise ratio (SNR) requirements in Stage 3: Fine-tune for required SNR, power, and refresh rate.
Filters are used to reduce the peak-to-peak noise; however, using filters will result in a higher scan time.
Figure 13. CAPSENSE™ Configurator - General settings
Note: Each tab has a Restore Defaults button to restore the parameters of that tab to their default values.
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Go to the CSD Settings tab and make the following changes:
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Set Inactive sensor connection as Shield.
Connect the inactive sensor, hatch pattern, or any trace that is surrounding the proximity sensor to the driven shield instead of connecting them to ground. This minimizes the signal due to the liquid droplets falling on the sensor.
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Set Shield mode as Active.
Setting the shield to active: The driven shield is a signal that replicates the sensor-switching signal. This minimizes the signal because of the liquid droplets falling on the sensor.
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Set Total shield count as 10 (Enabling all the inactive sensors as shield during CSD sensor scan).
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Select Enable CDAC auto-calibration and Enable compensation CDAC.
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Set Raw count calibration level (%) to 70.
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Select Enable CDAC dither.
This helps in removing flat spots by adding white noise that moves the conversion point around the flat-spots region. See the CAPSENSE™ design guide for more information.
Figure 14. CAPSENSE™ Configurator - Advanced CSD settings
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Go to the Widget Details tab.
Select Proximity0 from the left pane and then set the following:
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Sense clock divider: Retain the default value (will be set in Stage 2: Set sense clock frequency)
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Clock source: Direct
Note: Spread spectrum clock (SSC) or PRS clock can be used as a clock source to deal with EMI/EMC issues.
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Number of sub-conversions: 60
60 is a good starting point to ensure a fast scan time and sufficient signal. This value will be adjusted as required in Stage 3: Fine-tune for required SNR, power, and refresh rate.
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Proximity threshold: 65535
Proximity threshold is set to the maximum to avoid waking the device up from WoT mode because of touch detection; this is required to find the signal and SNR. This will be adjusted in Stage 4: Tune threshold parameters.
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Touch threshold: 65535
Touch threshold is also set to the maximum to avoid the waking up of the device from WoT mode.
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Noise threshold: 40
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Negative noise threshold: 40
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Low baseline reset: 65535
Low baseline reset is set to 65535 so that the baseline does not reset at all because of abnormal dips in raw count.
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Hysteresis: 40
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ON debounce: 3
Figure 15. CAPSENSE™ Configurator - Proximity Widget Details tab under the Advanced tab
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Go to the Scan Configuration tab to select the pins and scan slots. Do the following:
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Configure the pins for electrodes using the drop-down menu.
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Configure the scan slots using the Auto-assign slots option. The other option is to allot each sensor a scan slot based on the entered slot number.
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Select Proximity0_Sns0 as Ganged under the LowPower0 widget as shown in Figure 16.
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Check the notice list for warnings or errors.
Figure 16. Scan Configuration tab
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Click Save to apply the settings.
See the CAPSENSE™ design guide for detailed information on tuning parameters.
The sense clock is derived from the modulator clock using a clock-divider and is used to scan the sensor by driving the CAPSENSE™ switched capacitor circuits. Both the clock source and clock divider are configurable.
Select the maximum sense clock frequency such that the sensor and shield capacitance are charged and discharged completely in each cycle. This can be verified using an oscilloscope and an active probe. To view the charging and discharging waveforms of the sensor, probe at the sensor (or as close as possible to the sensors), and not at the pins or resistor.
Figure 21 shows proper charging when the sense clock frequency is correctly tuned, i.e., the voltage is settling to the required voltage at the end of each phase. Figure 22 shows incomplete settling (charging/discharging) and therefore, the sense clock divider is set to 28 as shown in Figure 21.
Figure 21. Proper charge cycle of a sensor
Figure 22. Improper charge cycle of a sensor
To set the proper sense clock frequency, follow these steps:
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Program the board and launch CAPSENSE™ Tuner.
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Observe the charging waveform of the sensor and shield as described earlier.
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If the charging is incomplete, increase the sense clock divider. Do this in CAPSENSE™ Tuner by selecting the sensor and editing the sense clock divider parameter in the Widget/Sensor Parameters panel.
Note:
- The sense clock divider should be divisible by 4. This ensures that all four scan phases have equal durations.
- After editing the value, click the Apply to Device button and observe the waveform again. Repeat this until complete settling is observed.
- Using a passive probe will add an additional parasitic capacitance of around 15 pF; therefore, should be considered during the tuning.
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Click the Apply to Project button so that the configuration is saved to your project.
Figure 23. Sense clock divider setting
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Repeat this process for all the sensors and the shield. Each sensor may require a different sense clock divider value to charge/discharge completely. But all the sensors which are in the same scan slot need to have the same sense clock source, sense clock divider, and number of sub-conversions. Therefore, take the largest sense clock divider in a given scan slot and apply it to all the other sensors that share that slot.
Table 5. Sense clock parameters obtained based on sensors for CY8CPROTO-040T kit
Parameter Value Modulator clock divider 1 Sense clock divider 28
The sensor should be tuned to have a minimum SNR of 5:1 and a minimum signal of 50 to ensure reliable operation. The sensitivity can be increased by increasing number of sub-conversions and noise can be decreased by enabling available filters.
The steps for optimizing these parameters are as follows:
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Measure the SNR as mentioned in the Operation section.
Measure the SNR by placing your hand above the proximity loop at maximum proximity height (35 mm in this case).
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If the SNR is less than 5:1 increase the number of sub-conversions. Edit the number of sub-conversions (Nsub) directly in the Widget/Sensor parameters tab of the CAPSENSE™ Tuner.
Note: Number of sub-conversion should be greater than or equal to 8.
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PSoC™ 4000T CAPSENSE™ has a built-in CIC2 filter which increases the resolution for the same scan time. This example has the CIC2 filter enabled.
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Load the parameters to the device and measure SNR as mentioned in steps 10 and 11 in the Monitor data using the Tuner Application section.
Repeat steps 1 to 4 until the following conditions are met:
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Measured SNR from the previous stage is greater than 5:1
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Signal count is greater than 50
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If the system is noisy (>40% of signal), enable filters.
Whenever the CIC2 filter is enabled, it is recommended to enable the IIR filter for optimal noise reduction. Therefore, this example has the IIR filter enabled as well.
To enable and configure filters available in the system:
a. Open CAPSENSE™ Configurator from ModusToolbox™ Quick Panel and select the appropriate filter.
Figure 24. Filter settings in CAPSENSE™ Configurator
Note : Add the filter based on the type of noise in your measurements. See ModusToolbox™ CAPSENSE™ Configurator user guide for details.
b. Click Save and close CAPSENSE™ Configurator. Program the device to update the filter settings.
Note : Increasing number of sub-conversions and enabling filters increases the scan time which in turn decreases the responsiveness of the sensor. Increase in scan time also increases the power consumption. Therefore, the number of sub-conversions and filter configuration must be optimized to achieve a balance between SNR, power, and refresh rate.
Various thresholds, relative to the signal, need to be set for each sensor. Do the following in CAPSENSE™ Tuner to set up the thresholds for a widget:
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Switch to the Graph View tab and select Proximity0.
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Place your hand at 40 mm directly above the proximity sensor and monitor the touch signal in the Sensor signal graph, as shown in Figure 25.
Figure 25. Sensor signal when hand is in the proximity of the sensor
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Note the signal measured and set the thresholds according to the following recommendations:
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Proximity threshold = 80% of the signal
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Proximity touch threshold = 80% of the signal
Here, the touch threshold denotes the threshold for the proximity sensor to detect a touch when it is touched by a finger. When the proximity sensor is touched, the sensor yields a higher signal compared the proximity signal; therefore, it is the touch signal. To measure the touch signal count, touch the sensor and monitor the signal in the Sensor signal graph.
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Noise threshold = 40% of the signal
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Negative noise threshold = 40% of the signal
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Hysteresis = 10% of signal
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Low baseline reset = 30 (by default)
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Hysteresis = 10% of the signal
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ON debounce = 3
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Apply the settings to the device by clicking To device.
Figure 26. Apply settings to device
If your sensor is tuned correctly, you will observe that the proximity status goes from
0to1in the Status sub-window of the Graph View window as Figure 27 shows. The successful tuning of the proximity sensor is also indicated by LED3 in the kit; it turn ON when the hand comes closer than the maximum distance and turn OFF when the hand is moved away from the proximity sensor.Figure 27. Sensor status in CAPSENSE™ Tuner showing proximity status
After touching the proximity loop, a further change in status from
1to3can be observed which indicates a touch. Along with this, LED1 will turn ON in blue color.Figure 28. Sensor status in CAPSENSE™ Tuner showing touch status
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Click Apply to Project as shown in Figure 29. The change is updated in the design.cycapsense file.
Close CAPSENSE™ Tuner and launch CAPSENSE™ Configurator. You should now see all the changes that you made in the CAPSENSE™ Tuner reflected in the CAPSENSE™ Configurator.
Figure 29. Apply settings to Project
Table 6. Tuning parameters obtained based on sensors for CY8CPROTO-040T kit
Parameter Proximity0 Proximity signal 150 Touch signal 3125 Proximity threshold 120 Touch threshold 2500 Noise threshold 60 Negative noise threshold 60 Low baseline reset 255 Hysteresis 15 ON debounce 3
This code example explains the tuning procedure for the proximity widget. See the PSoC™ 4: MSCLP low-power CSD button for tuning the low-power widget.
You can debug the example to step through the code.
In Eclipse IDE
Use the <Application Name> Debug (KitProg3_MiniProg4) configuration in the Quick Panel. For details, see the "Program and debug" section in the Eclipse IDE for ModusToolbox™ user guide.
In other IDEs
Follow the instructions in your preferred IDE.
The project contains the following widgets:
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Proximity widget with 1 electrode configured in CSD-RM Sensing mode.
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Low power widget with 1 electrode configured in CSD-RM Sensing mode.
See the Tuning procedure section for step-by-step instructions on configuring these widgets.
The project uses the CAPSENSE™ middleware; see the ModusToolbox™ user guide for more details on selecting a middleware.
See AN85951 – PSoC™ 4 and PSoC™ 6 MCU CAPSENSE™ design guide for more details of CAPSENSE™ features and usage.
The design also has an EZI2C peripheral and a PWM controlled LED. The EZI2C slave peripheral is used to monitor the information of sensor raw and processed data on a PC using the CAPSENSE™ Tuner available in the Eclipse IDE for ModusToolbox™ via I2C communication.
The PWM pin is used to control the brightness and ON/OFF operation of the LED.
The firmware is designed to support the following application states:
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Active state
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Active low-refresh rate state
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Wake-on-touch state
Figure 30. Firmware state-machine
The firmware state machine and the operation of the device in four different states are explained in the following steps:
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Initializes and starts all hardware components after reset.
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The device starts CAPSENSE™ operation in the Active state. In this state, the following steps occur:
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The device scans all CAPSENSE™ sensors present on the board.
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During the ongoing scan operation, the CPU moves to the Deep Sleep state.
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The interrupt generated on scan completion wakes the CPU which processes the sensor data and transfers the data to CAPSENSE™ Tuner through EZI2C.
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Turn ON the corresponding LEDs with specific brightness to indicate the specific proximity or touch detection.
In Active state, a scan of the selected sensors happen with the highest refresh rate of 128 Hz.
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Enters the Active low-refresh rate state when there is no touch or object in proximity detected for a timeout period. In this state, selected sensors are scanned with a lower refresh rate of 32 Hz. Because of this, power consumption in the Active low-refresh rate state is lower compared to the Active state. The state machine returns to the Active state if there is touch or object in proximity detected by the sensor.
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Enters the Wake-on-Touch state when there is no touch or object in proximity detected in Active low-refresh rate state for a timeout period. In this state, the CPU is set to deep sleep, and is not involved in CAPSENSE™ operation. This is the lowest power state of the device. In the Wake-on-Touch state, the CAPSENSE™ hardware executes the scanning of the selected sensors called "low-power widgets" and processes the scan data for these widgets. If touch is detected, the CAPSENSE™ block wakes up the CPU and the device enters to the Active state.
In the PSoC™ 4000T CAPSENSE™ Prototyping Kit, there are two onboard LEDs connected to PWM pins on the device. Therefore, the brightness and ON/OFF status of these LEDs can be controlled.
Figure 31. Firmware flowchart
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Open Device Configurator from the Quick Panel.
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Go to the System tab. Select the Power resource, and set the VDDA value under Operating conditions as shown in Figure 32.
Figure 32. Setting the VDDA supply in the System tab of Device Configurator
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By default, the debug mode is disabled for this application to reduce power consumption. Enable debug mode to enable SWD pins as shown in Figure 33.
Figure 33. Enable debug mode in the System tab of Device Configurator
Figure 34. EZI2C settings
Figure 35. PWM settings
Table 7. Application resources
| Resource | Alias/object | Purpose |
|---|---|---|
| SCB (I2C) (PDL) | CYBSP_EZI2C | EZI2C slave driver to communicate with CAPSENSE™ Tuner |
| SCB (SPI) (PDL) | CYBSP_MASTER_SPI | SPI master driver to control serial LEDs |
| CAPSENSE™ | CYBSP_MSC | CAPSENSE™ driver to interact with the MSC hardware and interface the CAPSENSE™ sensors |
| Digital pin | CYBSP_PWM | To show the proximity operation in the PSoC™ 4000T CAPSENSE™ Prototyping Kit |
| Resources | Links |
|---|---|
| Application notes | AN79953 – Getting started with PSoC™ 4 AN85951 – PSoC™ 4 and PSoC™ 6 MCU CAPSENSE™ design guide AN234231 – Achieving lowest-power capacitive sensing with PSoC™ 4000T AN92239 – Proximity sensing with CAPSENSE™ |
| 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 psoc4-middleware – Links to all PSoC™ 4 middleware |
| 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. |
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 title: CE238882 – PSoC™ 4: MSCLP low-power proximity
| Version | Description of change |
|---|---|
| 1.0.0 | New code example. |
| 2.0.0 | Major update to support ModusToolbox™ v3.2 and CAPSENSE™ Middleware v5.0. This version is not backward compatible with previous versions of ModusToolbox™ |
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