PICDEM Touch Sense 2 Demonstration Board
The PICDEM Touch Sense 2 Demo Board provides a simple platform for developing a variety of capacitive touch sense applications. Despite a simple and low part-count design, the Touch Sense 2 board shows how to implement USB-enabled touch applications with multiple outputs using a single microcontroller.
The USB connection supplies both communications and power to the board; no additional external power supply is needed. For independent operation, the demo board may be disconnected from the PC and powered at test points for independent functionality.
The PC side application that accompanies the demo board allows users to monitor the performance of the touch sensors and calibrate their response. A separate, 6-wire programming interface allows users to replace the pre-programmed demo firmware with their own applications, using Microchip’s MPLAB Integrated Development Environment and In-Circuit Serial Programming™ (ICSP™). This allows the board to also be used as a test bed for capacitive touch sense solutions.
Control of the touch sense features are built on the PIC24F microcontroller’s on-chip Charge Time Measurement Unit (CTMU) module. The CTMU consists of a constant
current source that charges the touch circuit to a fixed voltage level. When any additional capacitance is added to the circuit (from the touch of a fingertip, for example), the fixed current source will now charge the circuit to a lower voltage. This change is how the microcontroller detects a touch event.
The microcontroller uses the CTMU to monitor its analog input channels, which are in turn, connected to capacitive touch pad sensors on the top layer of the circuit board. The acrylic top layer protects the top layer of the PCB from direct contact, as well as visual cues of where to touch.
Key Applications: CapacitiveTouch Sense applications
Features
- Touch Sense 2 Demo Board has four different sensor demonstration areas:
- Directional Keypad
- Located at the bottom left side of the demo board, the directional keypad takes the form of an 8-point compass rose of red arrows surrounding a white circle.
- Above this is a second compass rose with white arrows instead of red.
- Touching any one of the arrows in the keypad causes the corresponding arrow in the upper compass rose to light up
- Numeric Keypad
- By board area, the largest application on the demo board is the numeric keypad.
- 20 touch-sensitive keys arranged in a 4x5 arbitrarily labelled, simple four-function calculator.
- Touching any one of the keypads causes it to be lit in its upper left corner and from beneath, accompanied by an audible tone.
- Touch Slider
- Located on the right side of the board, the touch slider resembles the upper portion of a large exclamation point.
- Touching the slider anywhere along its length causes it to be lit at that point.
- The light follows your finger as it moves up and down the slider and remains at the last position on the slider when you remove your finger.
- “Soft” Power Control
- At the far right side of the board is a touch control marked with the universal power switch symbol.
- Touching the control lights the pad and turns the demo board on and off.
- Directional Keypad
Ships With
- PICDEM Touch Sense 2 Demo Board
- PICDEM Touch Sense 2 Demo Board Documentation CD
- USB Cable