Cap Wheel 2 Click Board™

Capacitive sensors are a very popular method of controlling 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. The CAP Wheel 2 Click Board™ can find its place among many applications - for touch-activated lighting controls, process control, touch-activated control panels, toys and any other applications that need a switch or an encoder.

How Does The Cap Wheel 2 Click Board™ Work?

Although it looks simple at first glance, capacitive touch sensing is not an easy task. Many parameters need to be sampled, filtered, compared and processed before positive touch detection and its position are confirmed. To make this possible, the Cap Wheel 2 Click Board™ utilizes the IQS263B, ProxSense® IC, a 3-channel projected (or self) capacitive proximity and touch controller from Azoteq. This IC has some advanced features such as the auto drift compensation, up to 80Hz report rate, long proximity range, automatic adjustment for optimal performance (ATI), configurable 8-bit 2/3 channel slider or 3 channel scroll wheel. These features enable CAP Wheel 2 Click Board™ 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. 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 maximize performance, many routing requirements need to be met in the sensing electrodes design. The relation between the sensing elements in position and size is crucial. The CAP Wheel 2 Click Board™ is designed with these requirements in mind and electrodes are "Self-Capacitive Wheel" shaped.

The IQS263B IC interfaces to a master controller via a 3-wire (SDA, SCL, and RDY) serial interface bus that is I2C compatible, with a maximum communication speed of 400kbit/s. The host MCU can force a communication at any time, by pulling the RDY line low. The communication will start directly following the current conversion cycle. If the event is terminated by the watchdog timer, the device will reset.

After every power-on cycle, the device will recalibrate itself. It will take some time, so it should be taken into consideration when building custom applications. MikroElektronika provides libraries and the demo application, that can be used as a reference for any future designs.

As mentioned before, the CAP Wheel 2 Click Board™ is I2C compatible and uses SCL, SDA and RDY pins for communication which are routed to SCL, SDA and INT pin on mikroBUS respectively.

SPECIFICATIONS

PINOUT DIAGRAM

This table shows how the pinout on Cap Wheel 2 Click Board™ corresponds to the pinout on the mikroBUS socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
	NC	1	AN	PWM	16	NC
	NC	2	RST	INT	15	RDY	Ready Output
	NC	3	CS	RX	14	NC
	NC	4	SCK	TX	13	NC
	NC	5	MISO	SCL	12	SCL	I2C Clock
	NC	6	MOSI	SDA	11	SDA	I2C Data
Power Supply	3.3V	7	3.3V	5V	10	NC
Ground	GND	8	GND	GND	9	GND	Ground

ONBOARD SETTINGS AND INDICATORS