Cap Extend 3 click
PID: MIKROE-2883
Weight: 30 g
Cap Extend 3 click features four capacitive sensor pads integrated on the PCB, that can sense
touch through a variety of different materials. This click can sense touch through plastic, wood,
or even metal, thanks to the proprietary Metal over Capacitive technology. All these materials
can be used to protect the surface of the PCB and sensor pad traces, allowing implementation of
all kinds of human-machine interfaces and seamless integration of the touch-sensitive buttons
into various kinds of front panels. The click also features a connector used for connecting to
external sensors.
Features like the multi-stage active noise suppression filtering, automatic environmental
compensation, high signal-to-noise ratio (SNR) and support for a wide range of sensor pad
shapes and sizes, allow this device to be used as a reliable replacement for buttons or switches in
many applications, including light switches, office equipment and toys, display and keypad
backlight activation, and similar applications where a reliable and aesthetically pleasing button
alternative is required.
How does it work?
Cap Extend 3 click features the MTCH105, a five-channel proximity/touch controller with active
guarding capability, from Microchip. The MTCH105 IC uses a sophisticated scan optimization
algorithm to actively attenuate noise from the signal. Having a good SNR is one of the essential
prerequisites when implementing a reliable capacitive touch detection. Good SNR coupled with
the automatic environmental compensation, low power consumption and simple I/O interface
make this IC a perfect solution for building the Cap Extend 3 click with four reliable touchpad
sensors.
The surface of Cap Extend 3 click is protected with the acrylic glass. If a touch event is detected
on one of the sensors connected to input pins of the IC (MTI0 to MTI4), the state of the
corresponding channel output pin, (MTO0 to MTO4) will be pulled to a logic LOW level,
indicating that the channel has been activated - touch has been detected on that specific channel.
This will also be indicated by a LED, related to the activated channel. The output pins are
working in an open drain configuration, thus are pulled HIGH by the onboard resistors.
Although the IC has five channels, only four buttons are implemented, as one of the channels is
multiplexed with the active guard functionality. Guard control (GC) pin is multiplexed with the
MTO2 pin, while GUARD pin is multiplexed with the MTI2 pin. If the GC pin is pulled down to
a GND level, it will set the MTI2/GUARD pin into the GUARD mode, which can be used to
absorb the noise around the sensor pads. A PCB trace connected to this pin surrounds all the
sensor pads, providing active guarding and enhancing the SNR significantly. It should be noted
that when the Active Guard is activated, a LED on the MTO2 pin will be lit, indicating that the
Guard function is enabled.
A small onboard SMD jumper, labeled as JP2 can be left unpopulated, disconnecting the guard
pin from the network of PCB traces that surround the sensor pads. This option is useful when the
external sensor pads are used, or when the active guard function is not required so that the
MTI2/MTO2 can be used as additional external cap touch sensor.
Cap Extend 3 click also allows connecting of external sensors through the connector labeled as
J1. The MTCH105 itself allows sensors of various sizes and shapes to be used, as well as sensors
made of several different materials - carbon printing on plastic film, Indium Tin Oxide (ITO)
pad, wire/cable, etc. External sensors connector allows expanding touch capabilities of the Cap
Extend 3 beyond the click itself. All five channels are routed to this connector, so users can
decide on their preferred configuration of sensors and decide if the active guard feature will be
used or replaced by another sensor.
The sensitivity of the sensor pads can be adjusted via the onboard potentiometer, connected
between the VCC and GND. The potentiometer acts as a voltage divider, with its wiper
connected to the MTSA pin of the MTCH105. Raising the voltage level of this pin will result in
the lower sensitivity of the MTCH105 inputs.
The onboard SMD jumper labeled as the MODE SEL is used to select the working mode of the
device. The device can work in either normal or the low power mode. While working in normal
mode, the burst scan of the inputs will happen continuously, providing the shortest detection
time. When set to work in the low power mode, the device will have a delay of 256ms between
each burst scan interval. It will allow for significantly reduced power consumption, but the touch
detection can be longer in this case. The device will work in a normal mode, when the MTPM
pin is set to the VCC level, by switching the MODE SEL jumper to the position labeled as
HIGH. When the MODE SEL jumper is set to the position labeled as LOW, the MTPM pin will
be set to the GND level and the device will work in the low power mode.
The device also features a timeout reset. This function is useful when the sensor pad is
obstructed by a foreign object, or its state is otherwise stuck as activated. When the channel stays
activated for longer than 10 seconds, the corresponding channel will be reset and recalibrated.
All the five channel output pins of the MTCH105 are routed to the mikroBUS™ so that their
states can be read and detected by the MCU in an easy and simple way. The channels are routed
to the AN, PWM, INT, RST and CS pins of the mikroBUS™.
Specifications
Type
Proximity
It can be used as a reliable replacement for buttons or switches in many
applications, including light switches, office equipment and toys, display and
keypad backlight activation, and similar.
MTCH105, a 5-Channel Proximity/Touch Controller from Microchip
The device features multi-stage active noise suppression filtering, automatic
environmental compensation, high signal-to-noise ratio (SNR) and it can
sense touch through many different materials, including metal panels.
Applications
On-board modules
Key Features
Interface
Input Voltage
Click board size
GPIO
3.3V
L (57.15 x 25.4 mm)
Pinout diagram
This table shows how the pinout on Cap Extend 3 click corresponds to the pinout on the
mikroBUS™ socket (the latter shown in the two middle columns).
Notes
Sensor 0 state
Sensor 1 state
Sensor 2 state
Pin
TO0
TO1
TO2
NC
NC
NC
Power supply
Ground
+3.3V
GND
1
2
3
4
5
6
7
8
AN
RST
CS
SCK
MISO
MOSI
3.3V
GND
PWM
INT
RX
TX
SCL
SDA
5V
GND
16
15
14
13
12
11
10
9
TO3
TO4
NC
NC
NC
NC
NC
GND
Ground
Pin
Notes
Sensor 3 state
Sensor 4 state
Onboard settings and indicators
Label
LD1
LD2
LD3
LD4
Name
TO0
TO1
TO2
TO3
Default
-
-
-
-
Sensor 0 state indicator
Sensor 1 state indicator
Sensor 2 state indicator
Sensor 3 state indicator
Description
LD5
LD6
JP1
TO4
PWR
MODE SEL
-
-
Right
Sensor 4 state indicator
Power LED indicator
Mode selection, left (LOW) - low power mode, right (HIGH)
- normal power mode
Jumper used to connect the guard pin to the traces
network that surrounds sensor pads
1x5 header used for connecting sensor pads
JP2
J1
JP2
TOUCH SENSOR
Populated
Software support
We provide a library for Cap Extend 3 click on our LibStock page, as well as a demo application
(example), developed using MikroElektronika compilers and mikroSDK. The provided click
library is mikroSDK standard compliant. The demo application can run on all the main
MikroElektronika development boards.
Library Description
Initializes GPIO driver and click driver functions, which detect a touch on determined pins. For
more details, check the documentation.
Key functions
uint8_t
uint8_t
uint8_t
uint8_t
uint8_t
capextend3_Touch_0()
-
capextend3_Touch_1()
-
capextend3_Touch_2()
-
capextend3_Touch_3()
-
capextend3_Touch_4()
-
The function reads a state of the AN pin.
The function reads a state of the RST pin.
The function reads a state of the CS pin.
The function reads a state of the INT pin.
The function reads a state of the PWM pin.
Examples Description
The demo application is composed of three sections:
•
•
•
System Initialization - Initializes AN, RST, CS, PWM, INT pin as INPUT.
Application Initialization - Initializes GPIO Driver.
Application Task - (code snippet) - The USB UART shows the number of the button which is being
touched.
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