PICDEM™ TOUCH SENSE 2 DEMO
BOARD USER’S GUIDE
©
2008 Microchip Technology Inc.
DS51748A-page 19
Chapter 4. Demo Board Hardware
This chapter provides a functional overview of the PICDEM Touch Sense 2 Demo
Board and identifies the major hardware components. Topics covered include:
• Application Functional Overview
4.1
APPLICATION FUNCTIONAL OVERVIEW
Figure 4-1 illustrates the main functions of the Touch Sense 2 Demo Board:
FIGURE 4-1:
APPLICATION SIDE BLOCK DIAGRAM
The operation of the demo board is managed by the PIC24FJ256GB110
microcontroller, which requires very little additional hardware to perform its tasks. In
addition to the Touch Sense demo application code, the preloaded demo uses
substantial parts of the Microchip USB Stack Library to provide a hardware interface to
the PC-based interface application.
The Touch Sense application uses the microcontroller’s Charge Time Measurement
Unit (CTMU) and all 16 of the microcontroller’s A/D input channels to monitor the touch
interfaces. The CTMU functions by sensing small changes in capacitance on its inputs,
such as those occurring when a person touches the copper pad electrodes. By
continuously monitoring for these changes, the CTMU can determine when a touch
event occurs. The sensors on the Touch 2 Demo Board are comprised of carefully
placed circuit traces and capacitive touch pads, shown in Figure 4-2.
PIC24FJ256GB110
USB mini-B
Receptacle
Touch Keypad
ICSP™
D+/D-
Directional LEDs
RC1:RC4
RD6:RD7
RD12:RD13
AN0:AN8
PGC/EMUC
PGD/EMUD
MCLR
Numeric
J1
Programming
Header
Touch Keypad
AN9:AN10
Directional
Touch
AN11:AN14
Slider
Power Supply
D18/Q1
RG6
Slider
LED Matrix
Keypad
LED Matrix
D8-D33
D12-17, D39-64
D19-24, D26-27,
BZ1
Piezo Speaker
D38
RE0:RE8
RG7
RD1:RD5
RD8:RD1
Touch
Switch
Power
AN15
S20
ROT1
S14
S1-12, S21-27
