Designing with Touch Controls in Altium Designer

How many of us got into electronics because we were drawn by the myriad of cool switches, knobs, lights and other suitably gadget-centric controls? Fast forward a good few years and that allure is still there, only it is now replaced with the "Snazzy GUI" factor - electronic products that have a sleek, sexy interface. Central to these ever-advancing (and shrinking) product interfaces is touch control. Subtle yet powerful, touch control makes a product more efficient to use, typically lowers the manufacturing cost and, by virtue of replacing mechanical switches and dials – that are at the mercy of inevitable wear and tear – increases the life-span of that product. Pick up your favorite piece of smart technology and you will soon realize that without touch control, it would simply be, well, not so smart - and certainly far less engaging and fun.

Altium Designer provides support for creating planar capacitive sensor patterns on your PCB. The following vendors are supported:

  • Atmel Touch Controls – various self-capacitance and mutual-capacitance sensor patterns (buttons, wheels, sliders) are available, for use with Atmel® QTouch® and QMatrix® sensor controllers.
  • Cypress Touch Controls – various self-capacitance sensor patterns (buttons, sliders) are available, for use with Cypress® CapSense® controllers.
  • Microchip Touch Controls – various self-capacitance sensor patterns (ring, sliders) are available, for use with Microchip® mTouch® controllers.

Installing Touch Sensor Support

Touch Sensor support can be included as part of initial installation of Altium Designer. Simply ensure that the Touch Sensor Support option (for the required vendor(s)) is enabled, on the Select Design Functionality page of the Altium Designer Installer.

Add Touch Sensor support as part of initial installation of Altium Designer.
Add Touch Sensor support as part of initial installation of Altium Designer.

If support has not already been added during initial installation of the software, it can be added from the Configure Platform page, when managing the extensions and updates for your installation (click the Bobblehead icon button, at the top-right of the main application window, then choose the Extensions and Updates entry from the associated menu).

  1. From the Installed page of the view, simply click the Configure button at the top-right - to access the Configure Platform page.

    First access the Configure Platform page of the Extensions & Updates view.
    First access the Configure Platform page of the Extensions & Updates view.

  2. Scroll to the bottom of the page and enable the entry for Atmel QTouch, in the Touch Sensor Support region of the page.

    Then enable the Atmel QTouch option, under Touch Sensor Support.
    Then enable the Atmel QTouch option, under Touch Sensor Support.

  3. Click the Apply button, back at the top-right of the page. Altium Designer must be restarted for the changes to take effect, so click Yes at the dialog prompt. The required files will be downloaded and installed, and Altium Designer restarted. Verify through Windows Explorer that the IntLib library file is now available – in the associated folder in \Users\Public\Documents\Altium\AD<VersionNumber>\Library (for a default installation).

    After the installation is updated, the integrated libraries will be available.
    After the installation is updated, the integrated libraries will be available.

Installing touch sensor support for a particular vendor installs the relevant library of components needed for the different touch sensor technologies supported for that vendor, including touch wheels, sliders, and buttons. All components are configurable, allowing you to specify the size and orientations of the touch sensor geometries, in accordance with your design requirements.

Sensor Implementation

A touch sensor is implemented in a design by placing and configuring the required sensor type from a dedicated integrated library. Access to the associated configuration dialog (QTouch Component dialog, CapSense Component dialog, or mTouch Component dialog) for a sensor component by right-clicking over the component and choosing Configure from the context menu.

Note that while you can use the Sensor Component Type drop-down in the dialogs to quickly switch to a different sensor component type (the graphical symbol will update accordingly), the component's Comment and Description as well as the Design Item ID (for the linked library component) will remain reflective of, and reference, the original placed sensor type.

When configured as required, simply update the target PCB – an ECO is used to effect the required changes, resulting in the creation of the sensor pattern for placement on the PCB. Then it's just a case of placing the sensors on the board at the locations they are required to facilitate your product's user interface, then wiring them up to the applicable touch sensor controllers. Each sensor component on the PCB isn't a footprint in the normal sense, but rather the actual copper electrode pattern. An overlaying panel would be placed over a sensor when the board is assembled.

Although self-capacitance type sensor patterns can be used with or without an overlying panel, electrostatic discharge (ESD) implications - for the associated controller device - is a major influence for such a panel being used. For mutual-capacitance slider- and wheel-based sensors, multiple channels have unique X-electrode connections to the sensor controller, with a commoned Y-electrode connection. Such sensors should be used with an overlying panel, bonded with no air gaps. It is the panel that provides a suitable conduit for the electric fields between the X and Y electrodes.
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Implementing a touch control is a snap – just place the required sensor type component on the schematic, configure it as applicable to your design needs, then push the changes over to the PCB to obtain the sensor pattern.

A sensor pattern can also be modified on the PCB side, and the changes pushed back to the relevant schematic sheet through an ECO.

The following sections take a closer look at the configurable sensor components available for placement in a design, their configuration options, and the resulting sensor pattern obtained on the PCB side. In each case, the default configurations are presented.

Atmel Touch Controls

Th QTouch Component dialog provides controls to configure a touch sensor component on a schematic sheet when creating planar capacitive sensor patterns on your PCB for use with the range of Atmel® QTouch® and QMatrix® sensor controllers to which the corresponding electrodes from the sensor patterns connect.

Atmel Touch Controls – Supported Self-Capacitance Type Sensors

The following self-capacitance type sensors are supported for use in your PCB designs.

A button (or key) sensor is a zero-dimensional sensor. It has a single point of contact. Slider and wheel sensors are one-dimensional sensors – they detect movement of your finger along a single axis. A spatially-interpolated sensor uses the geometry of its electrodes to interpolate the electric fields. A resistively-interpolated sensor uses physical resistors to provide the interpolation.

Each channel (electrode) of these sensors has a single, direct connection to the sensor controller. Such sensors are non-directional, in terms of their emitted electric fields. Although they can be used with or without an overlying panel, electrostatic discharge (ESD) implications – for the associated controller device – is a major influence for such a panel being used.

All of these sensors are suited for use with Atmel QTouch sensor controllers.

Atmel Touch Controls – Supported Mutual-Capacitance Type Sensors

The following mutual-capacitance type sensors are supported for use in your PCB designs.

A button (or key) sensor is a zero-dimensional sensor. It has a single point of contact. Slider and wheel sensors are one-dimensional sensors – they detect movement of your finger along a single axis. A spatially-interpolated sensor uses the geometry of its electrodes to interpolate the electric fields. A resistively-interpolated sensor uses physical resistors to provide the interpolation.

Each of these sensors has X (transmit) and Y (receive) electrodes, with the mutual capacitance between X and Y measured by the sensor controller. For slider- and wheel-based sensors, multiple channels have unique X-electrode connections to the sensor controller, with a commoned Y-electrode connection. Such sensors should be used with an overlying panel, bonded with no air gaps. It is the panel that provides a suitable conduit for the electric fields between the X and Y electrodes.

All of these sensors are suited for use with Atmel QMatrix sensor controllers.

Cypress Touch Controls

The CapSense Component dialog provides controls to configure a touch sensor component on a schematic sheet when creating planar capacitive sensor patterns on your PCB for use with the range of Cypress® CapSense® and PSoC® controllers.

Cypress's CapSense Controllers – to which the corresponding electrodes from the sensor patterns connect – are based on the Programmable System-on-Chip (PSoC®) platform. CapSense Controller categories include:

  • CapSense®
  • CapSense® Plus
  • CapSense® Express
  • The families of PSoC® Controllers - PSoC® 1, PSoc® 3, PSoC® 4, and PSoC® 5LP (which replaced the PSoC® 5 family).

The following self-capacitance sensor types are available for use in your PCB designs.

A button sensor is a zero-dimensional sensor. It has a single point of contact. Slider sensors are one-dimensional sensors – they detect movement of your finger along a single axis.

Each channel (electrode) of these sensors has a single, direct connection to the sensor controller. Such sensors are non-directional, in terms of their emitted electric fields. Although they can be used with or without an overlying panel, electrostatic discharge (ESD) implications – for the associated controller device – is a major influence for such a panel being used.

All of these sensors are suited for use with Cypress CapSense and PSoC controllers.

Microchip Touch Controls

The mTouch Component dialog provides controls to configure a touch sensor component on a schematic sheet when creating planar capacitive sensor patterns on your PCB for use with the range of Microchip® mTouch® controllers. Microchip's mTouch Controllers – to which the corresponding electrodes from the sensor patterns connect – are typically PIC devices. The following self-capacitance sensor types are available for use in your PCB designs.

Slider sensors are one-dimensional sensors – they detect movement of your finger along a single axis.

Each channel (electrode) of these sensors has a single, direct connection to the sensor controller. Such sensors are non-directional, in terms of their emitted electric fields. Although they can be used with or without an overlying panel, electrostatic discharge (ESD) implications – for the associated controller device – is a major influence for such a panel being used.

All of these sensors are suited for use with Microchip mTouch controllers.

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