Cap Wheel Click Board™

Capacitive sensors are a very popular method of controling 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 8 LEDs array thatthe CAP Wheel Click Board™ has onboard is taken into account. The CAP Wheel 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 Click Board™ 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 and its position are confirmed. To make this possible, Cap Touch click utilizes the IQS333, ProxSense® IC, a 9-channel projected (or 7-channel self) capacitive proximity and touch controller from Azoteq. This IC has some advanced features such as the auto drift compensation, Long proximity range, Automatic adjustment for optimal performance (ATI), two Configurable 11-bit sliders/scroll wheels and more. These features enable the CAP Wheel Click Board™ to 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 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 Click Board™ is designed with these requirements in mind and electrodes are "Self-Capacitive Wheel" shaped.

The CAP Wheel Click Board™ also contains 8 LEDs whose function can be user-defined. LEDs are connected to PWM LED driver pins on IQS333 which means that the user can turn LEDs on or off and control illumination, using the dimming modes that IQS333 supports.

The IQS333 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 has the capability to 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 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. Besides that, CLR pin is available on board which is routed to RST pin on mikroBUS™ and used to master reset the IC.

SPECIFICATIONS

PINOUT DIAGRAM

This table shows how the pinout of the CAP Wheel 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
Master Clear	CLR	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