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CapSense Device and Method Selection Guide

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This application note guides you in choosing PSoC® devices and capacitive sensing methods for applications using PSoC CapSense technologies

This application note guides you in choosing PSoC® devices and capacitive sensing methods for applications using PSoC CapSense technologies

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  • pretty interesting read though,,for amateur designers,,, i looked into the main page http://www.cypress.com/ ,there is enough information about capsense devices,check out
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  • Capsense in detail,check out this link http://www.cypress.com/
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  • 1. CapSense™ Device and Method Selection Guide AN14459 Author: Ryan Seguine Associated Project: No Associated Part Family: CY8C201xx , CY8C20x34, CY8C21x34, CY8C24x94 GET FREE SAMPLES HERE Software Version: PSoC Designer™ 4.3 with EPCY8C20x34, EPCY8C24x94 and EPNUMv3 Associated Application Notes: AN2041, AN2209, AN2292 Application Note Abstract This application note guides you in choosing PSoC® devices and capacitive sensing methods for applications using PSoC ™ CapSense technologies. The CY8C21534-24PVXI is qualified for automotive Introduction applications. The CY8C20x34 is available in an extended ™ commercial range only. Both CY8C20x34 and CY8C21x34 Cypress offers the following four CapSense part families support up to 28 capacitive sensors and the CY8C24x94 capable of performing capacitive to digital conversion: supports up to 46 sensors.  ™ CY8C201xx – CapSense Express The CY8C201xx CapSense Express family supports IOs  configurable as Capacitive sensing inputs or as GPIOs for CY8C20x34 LED drive, interrupt output, wake-up on interrupt input and  other digital IO functionalities. These products support CY8C21x34 register based configuration through an I2C interface.  CY8C24x94 Cypress offers the following CapSense development tools for ease of use: Table 1 displays a high level comparison of PSoC CapSense devices.  PSoC Designer IDE containing CapSense User Parameters useful in determining the appropriate device Modules (UMs) for an application include:  PSoC Express with CapSense Integration  Number of capacitive sensors  CapSense Development Kits:  Necessary supply voltage  CY3218-CAPEXP1, CY3218-CAPEXP2, and  CY3218-CAPEXP3 for CY8C201xx Communication means  CY3203A for CY8C20x34  Non CapSense functionality required  CY3213A for CY8C21x34  Package size  CY3214 for CY8C24x94  Programmability versus Configurability Development tools allow designers to adjust parameters for each method pertaining to their application. These Table 1. High Level Comparison of PSoC CapSense parameters allow designers to configure the dynamic Devices baseline control, harsh environment firmware CY8C CY8C CY8C CY8C compensation, finger detection, slider and touchpad Parameter 201xx 20x34 21x34 24x94 configuration, and external passive component pin Additional selection. Lowest High Higher Highest Functionality Power Lowest Lowest Lower Low Consumption Package Smallest Smallest Smaller Small Sizes Voltage Input Lowest Lowest Lower Low Range March 18, 2008 Document No. 001-14459 Rev. *A 1 [+] Feedback
  • 2. AN14459 CapSense UMs utilize digital and analog resources. To Device Selection utilize the additional functions listed, reconfiguration may be required. This can be done either by using the Dynamic Use Table 9. CapSense Device Parameters on page 6 in Reconfiguration tool within the PSoC Designer Device Appendix A to choose the appropriate device. Editor, or referring to the appropriate technical reference Many users prefer PSoC because it can perform multiple manual and manually configuring the needed registers functions in a single device. Table 2 provides an overview within the application firmware. of real time device functions (or user modules) supported Many of the digital hardware functions can be recreated in by the Cypress development tools within each CapSense firmware. For example, to create a PWM, an internal clock device family. or timer’s interrupt can be configured to post periodically. Table 2. User Modules for Each CapSense Device Family Within the interrupt, the port pins drive can be toggled to achieve the desired frequency and duty cycle. 201xx 20x34 21x34 24x94 Function CapSense devices also have important distinctions in areas like system and CPU clocking and power supply ● Full-Speed USB options as detailed in Table 3. ● USB to UART Table 3. Device Clocking Overview Communication ● ● ● ● HW I2C Slave Feature 201xx 20x34 21x34 24x94 ● ● HW I2C Master 6 or 12 6,12, or System Clock 24 MHz ● ● ● HW SPI M & S MHz 24 MHz ● ● Max CPU Speed HW UART, RX, TX 12 MHz 24 MHz 24 MHz at 4.75-5.25V ● ● ● SW I2C N/A Max CPU Speed 12 MHz 12 MHz 12 MHz HW Counter/Timer 13- at 3.15-4.75V 8-32 bit 8-32 bit bit Max CPU Speed 3 MHz 3 MHz 3 MHz HW Timer w/ Capture 8-32 bit 8-32 bit at 2.4-3.15V Digital HW PWM (with 8-32 bit 8-32 bit All CapSense devices have robust capacitive sensing Deadband Option) methods. Choose your device based on the application Pseudo Random notes, and then decide the implementation method. 8-32 bit 8-32 bit Sequencer LED (Including 7- ● ● ● Segment Support) Miscellaneous 20x2 LCD Controller ● ● ● Interface ● ● ● E2PROM Emulation ● ● ● I2C Bootloader Full-Speed USB ● Bootloader ADC 8 and 7 to 13 10 bit bit Analog / Mixed Signal DAC 6, 8, and 9 bit ● ● ● Comparators Amplifiers ● (Programmable Gain and Instrumentation ) 2-pole Band and Low ● Pass Filter CSR (Relaxation ● ● CapSense Oscillator) ● ● CSD (Sigma Delta) CSA (Successive ● ● Approximation) March 18, 2008 Document No. 001-14459 Rev. *A 2 [+] Feedback
  • 3. AN14459 Method Selection Table 6. Method Performance in Harsh Environments PSoC supports two capacitive sensing methods listed here: CSA CSA CSD CSD External Stimulus  201xx 20x34 21x34 24x94 Successive Approximation Radiated RF Excellent Excellent Excellent Excellent  Immunity (1.9GHz) Sigma-Delta Modulator Radiated RF Excellent Excellent Excellent Excellent Each sensing methods has an associated PSoC Designer Immunity (800MHz) UM to help designers configure the PSoC for the sensing Radiated RF method. They are: Excellent Excellent Excellent Excellent Immunity (144MHz)  CSA – CapSense with Successive Approximation Radiated RF Excellent Excellent Excellent Excellent Immunity (90kHz)  CSD – CapSense with Sigma-Delta Modulator AC Conducted Mains Excellent Excellent Excellent Excellent Immunity (50/60Hz) Table 4 lists the sensing methods supported by each AC Conducted Noise PSoC device. For details on the UM parameters, block Good Good Good Good Immunity (10kHz- placement and usage, and application programming 1MHz) interfaces (APIs), see the associated UM datasheets Power Supply contained within PSoC Designer. Excellent Excellent Excellent Excellent Transient Table 4. Available Methods for Each CapSense Device GPIO Load Transient Excellent Excellent Excellent Excellent Device CSD Method CSA Method ESD Air Discharge to Horizontal Ground Excellent Excellent Excellent Excellent ● CY8C201xx Plane ● CY8C20x34 ESD Contact Excellent Excellent Excellent Excellent Discharge to ● CY8C21x34 CapSense Overlay ● CY8C24x94 ESD Air Discharge to Excellent Excellent Excellent Excellent Exposed Ground Pin Temperature Note The CapSense with a Relaxation Oscillator (CSR) Good Good Excellent Excellent Response UM is not recommended for new designs. Contact your local Cypress FAE for guidance or more details. Radiated RF Excellent Excellent Excellent Excellent Immunity (1.9GHz) CSA and CSD are the recommended capacitive sensing Radiated RF methods. They perform extremely well in harsh and noisy Excellent Excellent Excellent Excellent Immunity (800 MHz) environments, require only minimal external passive Radiated RF components and are configurable for varying button sizes. Excellent Excellent Excellent Excellent Immunity (144 MHz) Table 5 provides an overview of the performance of each Radiated RF method in a typical application. Performance is influenced Excellent Excellent Excellent Excellent Immunity (90 kHz) by sensor layout, the overlay material and thickness, the AC Conducted Mains update rate, and resolution. Excellent Excellent Excellent Excellent Immunity (50/60 Hz) To validate the methods, Cypress has created a harsh AC Conducted Noise environment performance specification. These tests Excellent Excellent Good Good Immunity evaluate how each method performs against various (10 kHz-1 MHz) external stimuli. Relative comparisons of each method Power Supply based on the results of these tests are shown in Excellent Excellent Excellent Excellent Transient Table 6. GPIO Load Transient Excellent Excellent Excellent Excellent ESD Air Discharge to Table 5. Method Performance Excellent Excellent Excellent Excellent Horizontal Ground Plane CSA CSA CSD CSD Feature ESD Contact 201xx 20x34 21x34 24x94 Excellent Excellent Excellent Excellent Discharge to Power CapSense Overlay Excellent Excellent Excellent Excellent Consumption ESD Air Discharge to Excellent Excellent Excellent Excellent Typical SNR Exposed Ground Pin Excellent Excellent Excellent Excellent (1mm Overlay) Temperature Good Good Excellent Excellent Typical SNR Response Excellent Excellent Excellent Excellent (3mm Overlay) March 18, 2008 Document No. 001-14459 Rev. *A 3 [+] Feedback
  • 4. AN14459 Development CSA and CSD Differentiation To develop a PSoC CapSense design, download and While CSA and CSD are both robust capacitive sensing install the PSoC Designer or PSoC Express development methods, they differ in their applicability to certain designs. tool. This section discusses similarities, drawbacks, and advantages of the two sensing methods. CapSense in PSoC Express Both CSA and CSD create a switched capacitor circuit PSoC Express brings the simplicity of block based design using the sensing capacitor, switching it between a voltage to microcontrollers. It is a useful tool that allows designers rail and a measuring node. Because the clock has a 50% unfamiliar with real time embedded systems to quickly duty cycle, during half of the scan the sensing capacitor is build a functional design. All CapSense methods are connected to a voltage rail. This reduces the input supported in this development tool. impedance, reducing the amplitude of external noise seen To use a PSoC CapSense sensor in the PSoC Express, in measurement data. place the appropriate CapSense Sensor Inputs and the The CSD circuit uses many of the available resources in CapSense Properties Input. Similar to the Device Editor the CY8C21x34 device. It uses the VC clocks, three digital User Module properties, all relevant parameters are blocks, one comparator, both comparator columns, and configurable through the Properties Input. the ADC PWM. Projects that require an ADC must re- Support for CapSense Express devices is provided in the configure the CSD into an ADC and then back. The VC3 PSoC Express 3.0 software tool. This tool has various interrupt is unavailable for loop timing, unless the same drivers to configure these devices. For details refer to the settings are used for VC clock settings and CSD. Another application note CapSense Express Software Tool - way of doing this is; the extra digital block can be AN42137. You can tune all CapSense related parameters configured as a timer or the low-speed 32 kHz oscillator in real time to adjust sensitivity using this tool. (calibration is recommended if the 32 kHz oscillator is used for this type of application). CapSense in PSoC Designer In the CY8C24x94 device, there is a hardware decimator, PSoC Designer is an integrated development environment and a comparator reference based on Vdd. This reduces (IDE) complete with a debugger and application editor resource consumption by one digital block and one analog supporting C programming language and assembly column. However, the VC clocks are still used. language. CSD has two features that CY8C20x34 does not possess. PSoC Designer also includes an innovative device editor First, it uses a pseudo-random clock for its switching clock which allows users to configure PSoC for initialization and as well as its measurement clock. This reduces all to add prepackaged real time functions or user modules to radiated emissions except for the main oscillator PSoC projects. frequency. The PSoC CapSense UMs are placed using the device Second, the CSD provides a means to output a clock at its editor. After the UM is placed, sensors are assigned to switching frequency. If this clock is connected to a shield pins using the CapSense wizard. Set the parameters sensor surrounding the actual sensor, the count output governing the UM configuration. Table 7 lists the UM from the CSD will differentiate between smaller non- parameters. grounded objects (like metal disks or water) and larger Table 7. User Module Parameters Supported by Each grounded objects (like humans). Please see application Method note AN2398, Waterproof Capacitive Sensing. 201xx 20x34 21x34 24x94 CSA CSA CSD CSD The CSA sensing method uses a non-linear approach to Parameter measure the change in capacitance. A small change in capacitance produces an exponentially larger change in ● ● ● ● Sensor Debounce measurement counts. See Figure 1 on page 5 for a ● ● ● ● ESD FW Detection comparison of the capacitance response for each method. See Table 8 on page 5 for equations describing each Finger-on Startup ● ● ● ● curve. Recovery ● ● ● ● Note Unless waterproof sensing is required by the Sensor Auto Reset application, the device selection may be used to determine Shield Sensor for Wet ● ● the appropriate sensing method. Environments Independent Finger ● ● ● ● Thresholds for Buttons Configurable Finger On ● ● ● ● Hysteresis ● ● Sensor Auto Calibration Configurable Interpolated ● ● ● ● Position Touchpad Capability ● ● ● (Multiple Sliders) March 18, 2008 Document No. 001-14459 Rev. *A 4 [+] Feedback
  • 5. AN14459 Table 8. CapSense Response Linearity and Sensitivity Equations Linearity Sensing Sensitivity/Resolution Max. CS (Counts Method (Farads/Count) (Farads) vs. CS) 2 VREF FIMOCbus I dacCS Non- CSA linear I dac I DAC Cbus FIMO 1 kd 1 1 CSD Linear 1)2 N RES FS Rb ( 1 k d FS Rb kd Figure 1. Capacitive Response Method Comparison 7000 6000 5000 4000 Counts 3000 2000 1000 0 0 5 10 15 20 25 Added Capacitance (pF) CSA CSD Summary When using PSoC for capacitive sensing, any of the four device families available provide a robust sensing method in CSA and CSD. Choose your device, based on the package, feature set, and power needs you require. PSoC is not just a capacitive sensing device; it is an ADC, a full-speed USB device, an LED pulse controller, a frequency counter and more. March 18, 2008 Document No. 001-14459 Rev. *A 5 [+] Feedback
  • 6. AN14459 Appendix A: CapSense Device Parameters Table 9. CapSense Device Parameters CSA CSD Temp. CapSense Part Device Package IO RAM Flash Family Sensors Sensors Range Vdd Range CY8C20110-LDX2I 10 10 N/A Com-Ex 2.4-5.25 512 2K 16 QFN(3x3) CY8C20110-LDX2I 10 10 N/A Com-Ex 2.4-5.25 512 2K 16 SOIC CY8C20140-LDX2I 16 QFN(3x3) 4 4 N/A Com-Ex 2.4-5.25 512 2K CY8C20140-SX2I 16 SOIC 4 4 N/A Com-Ex 2.4-5.25 512 2K CY8C201xx CY8C20142-SX1I 4 4 N/A Com-Ex 2.4-5.25 512 2K 8 SOIC CY8C20160-LDX2I 6 6 N/A Com-Ex 2.4-5.25 512 2K 16 QFN(3x3) CY8C20160-SX2I 6 6 N/A Com-Ex 2.4-5.25 512 2K 16 SOIC CY8C20180-LDX2I 8 8 N/A Com-Ex 2.4-5.25 512 2K 16 QFN(3x3) CY8C20180-SX2I 16 SOIC 8 8 N/A Com-Ex 2.4-5.25 512 2K CY8C201A0-SX2I 16 SOIC 10 10 N/A Com-Ex 2.4-5.25 512 2K CY8C20x34 CY8C20234-12LKX 16 QFN(3x3) 13 13 N/A Com-Ex 2.4-5.25 512 8K CY8C20334-12LFXC 24 QFN(4x4) 20 20 N/A Com-Ex 2.4-5.25 512 8K CY8C21634-24LFXI 32 QFN(5x5) 28 28 N/A Com-Ex 2.4-5.25 512 8K CY8C21234-24SXI 16 SOIC 12 N/A 10 Ind 2.7-5.25 512 8K CY8C21334-24PVXI 20 SSOP 16 N/A 14 Ind 2.7-5.25 512 8K CY8C21x34 CY8C21534-24PVXI 28 SSOP 24 N/A 22 Ind 2.7-5.25 512 8K CY8C21434-24LFXI 32 QFN(5x5) 28 N/A 26 Ind 2.7-5.25 512 8K CY8C21634-24LFXI 32 QFN(5x5) 28 N/A 24 Ind 2.7-5.25 512 8K CY8C21334-12PVXE 20 SSOP 16 N/A 14 Auto 4.75-5.25 512 8K CY8C21534-12PVXE 28 SSOP 24 N/A 22 Auto 4.75-5.25 512 8K CY8C24794-24LFXI 56 QFN(8x8) 50 N/A 46 Ind 3.0-5.25 1K 16K CY8C24x94 CY8C24894-24LFXI 56 QFN(8x8) 49 N/A 45 Ind 3.0-5.25 1K 16K CY8C24994-24LFXI 68 QFN(8x8) 56 N/A 46 Ind 3.0-5.25 1K 16K 100 VFBGA CY8C24994-24BVXI 56 N/A 46 Ind 3.0-5.25 1K 16K (6x6) March 18, 2008 Document No. 001-14459 Rev. *A 6 [+] Feedback
  • 7. AN14459 About the Author Name: Ryan Seguine Title: Product Manager, Senior Background: BS, University of Washington Contact: capsense@cypress.com PSoC is a registered trademark of Cypress Semiconductor Corp. quot;Programmable System-on-Chip,quot; PSoC Designer, and PSoC Express are trademarks of Cypress Semiconductor Corp. All other trademarks or registered trademarks referenced herein are the property of their respective owners. Cypress Semiconductor 198 Champion Court San Jose, CA 95134-1709 Phone: 408-943-2600 Fax: 408-943-4730 http://www.cypress.com/ © Cypress Semiconductor Corporation, 2007-2008. The information contained herein is subject to change without notice. Cypress Semiconductor Corporation assumes no responsibility for the use of any circuitry other than circuitry embodied in a Cypress product. Nor does it convey or imply any license under patent or other rights. Cypress products are not warranted nor intended to be used for medical, life support, life saving, critical control or safety applications, unless pursuant to an express written agreement with Cypress. Furthermore, Cypress does not authorize its products for use as critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress products in life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress against all charges. This Source Code (software and/or firmware) is owned by Cypress Semiconductor Corporation (Cypress) and is protected by and subject to worldwide patent protection (United States and foreign), United States copyright laws and international treaty provisions. Cypress hereby grants to licensee a personal, non-exclusive, non-transferable license to copy, use, modify, create derivative works of, and compile the Cypress Source Code and derivative works for the sole purpose of creating custom software and or firmware in support of licensee product to be used only in conjunction with a Cypress integrated circuit as specified in the applicable agreement. Any reproduction, modification, translation, compilation, or representation of this Source Code except as specified above is prohibited without the express written permission of Cypress. Disclaimer: CYPRESS MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARD TO THIS MATERIAL, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Cypress reserves the right to make changes without further notice to the materials described herein. Cypress does not assume any liability arising out of the application or use of any product or circuit described herein. Cypress does not authorize its products for use as critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress’ product in a life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress against all charges. Use may be limited by and subject to the applicable Cypress software license agreement. March 18, 2008 Document No. 001-14459 Rev. *A 7 [+] Feedback