When designing capacitive touch sense technology into your application, it is crucial to keep in mind that the CapSense device exists within a larger framework. Careful attention to every level of detail from PCB layout to user interface to end-use operating environment will lead to robust and reliable system performance. For more in-depth information, refer
Getting Started with CapSense.
What is SmartSense™?Cypress's revolutionary, patent-pending SmartSense™ auto-tuning algorithm, which eliminates the requirement for system tuning. SmartSense enables automatic tuning of more than 10 parameters to achieve optimal touch sensing performance.
SmartSense™ Advantages 1. Auto-tuning: Competitor solutions require FW changes / use of interface boards for configuration changes, SmartSense takes care of the tuning without user intervention.
2. Time Saver: Saves a lot of time by avoiding manual tuning during development.
3. Process change: No re-tuning required when there is PCB process change / PCB vendor change (for cost reasons) / sensor characteristics change.
4. Overlay change: No re-tuning required when overlay material or thickness change.
5. Environment change: No re-tuning needed when the noise conditions change making the CapSense module
What is CapSense Tuner?The graphical CapSense software module in Cypress's PSoC Creator™ IDE makes it easy for designers to define combinations of buttons, sliders, touch pads and proximity-sensing capacitive sensors, and offers real-time feedback of parameters such as signal-to-noise ratio (SNR), finger threshold, noise threshold, and more.
The module features include: 1. Supports user defined combinations of button, slider, touch pad, and proximity capacitive sensors
2. Provides automatic SmartSense tuning or manual tuning
3. High immunity to AC power line noise, EMC noise, and power supply voltage changes
4. Optional two scan channels (parallel synchronized) increases sensor scan rate.
5. Shield electrode support for reliable operation in the presence of water film or droplets
6. Guided sensor and terminal assignments using the CapSense customizer
1. Overlay Selection
| | • To increase the CapSense signal strength, choose an overlay material with a higher dielectric constant, decrease the overlay thickness, and increase the button diameter. Conductive material cannot be used as an overlay because it interferes with the electric field pattern. For this reason, do not use paints containing metal particles in the overlay.
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2. ESD Protection
| | • Robust ESD tolerance is a natural by-product of thoughtful system design. By considering how contact discharge will occur in your end product, particularly in your user interface, it is possible to withstand an 18-kV discharge event without incurring any damage to the CapSense controller.
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3. Electromagnetic Compatibility Considerations
| | • Radiated Interface: Radiated electrical energy can influence system measurements and potentially influence the operation of the processor core.
• Radiated Emissions:Selecting a low frequency for the switched capacitor clock will help to reduce radiated emissions from the CapSense sensor.
• Conducted Immunity and Emissions: Noise entering a system through interconnections with other systems is referred to as conducted noise. These interconnections include power and communication lines. Because CapSense controllers are low-power devices, conducted emissions must be avoided.
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4. Software Filtering
| | • Software filters are one of the techniques for dealing with high levels of system noise.
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5. Power Consumption
| | • From the system design perspective, methods to reduce power includes: set GPIO drive mode for low power, turn off the high-power blocks, optimize CPU speed, etc.
• In typical applications, the CapSense controller does not need to always be in the active state. The device can be put into the sleep state to stop the CPU and the major blocks of the device.
• In any application, if both power consumption and response time are important parameters to be considered, an optimized method can be used that incorporates both continuous-scan and sleep-scan modes.
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6. Pin Assignment
| | • An effective method to reduce interaction between CapSense sensor traces and communication and non-CapSense traces is to isolate each by port assignment.
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