MIKROE-2888 datasheet, PDF - EEWORLD Datasheet

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MIKROE-2888: DescriptionCAP TOUCH CLICK; CategoryDevelopment board/suite/development tools; File Size662KB，6 Pages; ManufacturerMikroElektronika; Websitehttps://www.mikroe.com; Environmental Compliance

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MIKROE-2888 Overview

CAP TOUCH CLICK

MIKROE-2888 Parametric

Parameter Name	Attribute value
platform	mikroBUS™ Click™
type	sensor
Function	capacitive touch
IC/parts used	AT42QT1010
content	plate

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Cap Touch click

PID: MIKROE-2888

Weight: 27 g

Cap Touch click is a capacitive touch sensing button, integrated on a click board™. It can be

activated by touch. This click can sense touch even through plastic, wood, or other dielectric

materials, which can be used to protect the surface of the PCB and the sensor pad trace

itself. Unlike the mechanical button, the capacitive touch button lasts much longer, it is not

prone to damage and wear over time and it is very reliable.

Capacitive buttons are a very popular method of powering up various devices. Besides the

aforementioned benefits, having a touch sensitive button on a device allows for a compact

design, opens possibilities for various kinds of human-machine interface and - it looks good and

modern, especially if accompanied by a LED that turns on when activated, just like the one on

Cap Touch click. Cap Touch click can find its place among many applications - for touch

activated lighting controls, touch activated control panels, toys and any other applications that

need a switch or a button.

How does it work?

Although it looks simple at first glance, capacitive touch sensing is not an easy task. There are

many parameters that need to be sampled, filtered, compared and processed before positive touch

detection is confirmed. To make this possible, Cap Touch click utilizes the AT42QT1010, a

single-key QTouch® touch sensor IC from Microchip. This IC has some advanced features such

as the self-calibration, auto drift compensation, noise filtering and proprietary QTouch®

technology, based on the patented charge-transfer method. These features enable Cap Touch

click exhibit very reliable and accurate touch detection.

Capacitive touch sensing is based on detecting a change in capacitance, due to the influence of a

foreign object. Basically, the capacitance of the sensor, also known as the antenna, is measured

and monitored and if a significant change occurs, after processing by the detection integrator, a

touch event is acknowledged. To successfully perform the detection, many routing requirements

need to be met, as the relation between the sensing elements in position and size is crucial. Cap

Touch click is designed with these requirements in mind, so it could successfully detect a touch.

This IC uses short bursts to monitor the capacitance and it features three modes of operation:

Fast mode, Low Power mode and SYNC mode. Switching between Fast and Low Power mode is

done by pulling the SYNC/MODE pin, routed to the mikroBUS™ PWM pin, to a HIGH or

LOW logic level, respectively:

- Fast mode yields the fastest detection time, yet it uses the most power, as the device

continuously sends measuring bursts, with about 1ms of delay between them. The device will

work in this mode if the PWM pin stays permanently at HIGH logic level.

- Low Power mode will send measurement bursts with about 80mS delay in between,

significantly lowering the power consumption, as well as the responsiveness of the device.

However, when a touch is detected, the device will enter the Fast mode again, allowing the

detection integration to detect a valid touch event. The device will work in Low Power mode if

the PWM pin stays permanently at LOW logic level.

- SYNC mode is used to control the measurement bursts timing by the clock signal provided on

the PWM pin. It is sed to reduce crosstalk when using more devices, or to enhance noise

immunity from low-frequency sources, such as 50Hz or 60Hz mains signals.

The output of the device is routed to the INT pin of the mikroBUS™. The output pin is active

high - on a valid detection it will be set to a HIGH logic level. The output will stay at the HIGH

level as long as the touch event is active (touch hold) and will be terminated by the Max On

duration feature - a timer that is set to about 60 seconds. If the event is terminated by the Max On

duration feature, the device will be recalibrated. The Max On duration feature is normally used

to resolve issues when the button detects an event for too long. If an object obstructs the sensor

pad - e.g. when a protective plastic layer is added, this feature will recalibrate the sensor so it

accommodates for this plastic layer.

After every power on cycle, the device will recalibrate itself. It will take some time, so it should

be taken into a consideration when building custom applications. MikroElektronika provides

libraries and the demo application, that can be used as a reference for any future designs.

The output of this device is too weak to drive a LED. Yet, a touch button is not good without the

LED or other indication of its state. In order to drive a LED, Cap Touch click is equipped with

the N-type MOSFET transistor, which is activated by the output pin of the AT42QT1010 IC. It

can drive one red LED without a problem.

The onboard SMD jumper labeled as VCC SEL is used to select the operating voltage of the

device. It is capable of working with both 3.3V and 5V capable MCUs. Besides PWM pin, used

for mode selection and the INT pin, used to signal the button state to the MCU, no other lines of

the mikroBUS™ are used.

Specifications

Type

Applications

On-board

modules

Capacitive

It can be used for touch activated lighting controls, touch activated control panels, toys

and any other applications that need a switch or a button.

AT42QT1010, a single-key QTouch® touch sensor IC from Microchip

Patented QTouch® sensing technology allows for low power consumption, auto

calibrating and detection integration algorithms which improve touch sensing quality,

Max ON duration for improved obstacle problem handling.

GPIO

Key Features

Interface

Input Voltage 3.3V or 5V

Click board

size

M (42.9 x 25.4 mm)

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