PR28
Tic-Tac-Toe with mTouch
Version 1.0
June 2010
Cytron Technologies Sdn. Bhd.
Information contained in this publication regarding device applications and the like is intended through suggestion only and may be superseded by
updates. It is your responsibility to ensure that your application meets with your specifications. No representation or warranty is given and no liability is
assumed by Cytron Technologies Incorporated with respect to the accuracy or use of such information or infringement of patents or other intellectual
property rights arising from such use or otherwise. Use of Cytron Technologies’s products as critical components in life support systems is not
authorized except with express written approval by Cytron Technologies. No licenses are conveyed, implicitly or otherwise, under any intellectual
property rights.
FEATURES
OVERVIEW
This document describes the development of Cytron
Technologies DIY (Do It Yourself) Project PR28. This
project demonstrates hobbyist on how to build a simple
Microchip’s mTouch where no extra components are
needed excluding the sensing pads on PCB. In this
project, capacitive sensing module (CSM) is used. Tic
Tac Toe game is one of the simple applications of
mTouch. This DIY project will be using PIC 16F727
microcontroller, 74HC595 shift registers, piezo, mTouch,
RGB LEDs and 2 x 16 characters LCD.
PIC16F727
- 8-bit microcontroller with 35 I/O
- Operates with 5V supply
- Operating speed 20MHz
- mTouch Sensing Oscillator Module which is
up to 16-input channels
74HC595 Shift Register
- 8-bit serial input
- 8-bit serial or parallel output
- Shift register with direct clear
Capacitive Touch Sensor (mTouch™)
- Made up from copper sensor pads
Created by Cytron Technologies Sdn. Bhd. – All Rights Reserved
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PR28 – Tic-Tac-Toe with mTouch
SYSTEM OVERVIEW
74 HC 595
mTouch™
PIC16F727
RGB LEDs
LCD
Piezo
GENERAL DESCRIPTION
PR28 is an open-sourced microcontroller Do It Yourself
kit. This PIC microcontroller based project is designed to
develop a Tic-Tac-Toe game using mTouch. mTouch,
also known as capacitive touch sensor, can replace
mechanical buttons with capacitive alternative. In
addition, it helps in cost reduction. mTouch has become
more prevalent and in demand for commercial
applications such as mobile devices and mp3 players.
Thus, this project will show users how to work with
mTouch. For information, PR28 uses internal oscillator
to run the program.
PIC16F727
This powerful (200 nanosecond instruction execution)
yet easy-to-program (only 35 single word instructions)
CMOS FLASH-based 8-bit microcontroller with nanoWatt XLP Technology packs Microchip's powerful PIC®
architecture into a 28- or 40- or 44-pin package and is
upwards compatible with the 28- or 40- pin PIC16CXX
and PIC16FXXX Microcontrollers. Features of the
device:
•
•
•
•
•
•
•
Interrupt capability
8-Level Deep Hardware Stack
Direct, Indirect or Relative Addressing modes
Processor Read Access to Program Memory
Precision Internal Oscillator
a. 16MHz or 500kHz operation
b. Factory calibrated to ±1%, typical
c. Software tunable
d. Software selectable +1, +2, +4 or +8
divider
Multiplexed Master Clear with Pull-up or Input
Pin
14 channels of 8-bit Analog-to-Digital (A/D)
converter where conversion is also available
during sleep mode
•
•
•
•
•
Enhanced Timer1:
a. Dedicated low-power 32 kHz
oscillator
b. 16-bit timer/counter with pre-scaler
c. External Gate Input mode with
toggle and single shot modes
d. Interrupt-on-gate completion
2 capture/compare/PWM functions
Synchronous Serial Port (SSP):
a. SPI (Master/Slave)
b. I²C™ (Slave) with Address Mask
Addressable
Universal
Asynchronous
Receiver Transmitter (AUART).
mTouch™ Sensing Oscillator Module which
is up to 16 input channels
40-pin PDIP (PIC 16F727)
Figure 1
Figure 1 shows the pin diagram for PIC16F727. For
more information about the PIC microcontroller, please
refer to the datasheet. The datasheet can be found in
microchip web site at: http://www.microchip.com
Created by Cytron Technologies Sdn. Bhd. – All Rights Reserved
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PR28 – Tic-Tac-Toe with mTouch
74HC595 Shift Register
Push Button
microcontroller
74HC595 shift register is the cheapest and easiest way to
extend I/O ports if user is running out of I/O pins. Using
this 8-bit shift register, user can control 8 outputs at a
time while only taking up 3 I/O ports on microcontroller.
Features of this device are as follows:
• 8-bit serial input
• 8-bit serial or parallel output
• Storage register with 3-state output
• Shift register with direct clear
• 100MHz (typical) shift out frequency
• Output capability
a. Parallel outputs; bus driver
b. Serial outputs; standard
• Icc category: MSI
For more information on 74HC595 shift register, please
refer to the datasheet which is available at the website
http://www.nxp.com/documents/data_sheet/74HC_HCT5
95.pdf
Capacitive Touch Sensor (mTouch™)
The construction of mTouch™ only consists of copper
pads on PCB board. There is no extra components
needed to make the mTouch™ functions. The detailed
explanation on how to work with mTouch™ will be
discussed in later section.
Power supply for the circuit
as
input
for
PIC
Figure 4
One push button needs one I/O pin to be used as an
input for PIC microcontroller. The connection of the
push button to the I/O pin is shown in Figure 3. The
I/O pin should be pulled up to 5V using a resistor (with
value range 1K-10K) and this configuration will result
in an active-low input. When the button is being
pressed, reading of I/O pin will be in logic 0, while
when the button is not pressed, reading of that I/O pin
will be logic 1.
ICSP
for
microcontroller
programming
PIC
Figure 5
Figure 3
User can choose either AC to DC adaptor (not included
in the DIY project set) or 9V-12V battery (not included
in the DIY project set) to power up the circuit. Higher
input voltage will produce more heat at LM7805 voltage
regulator. Typical voltage is 12V. Anyhow, LM7805 will
still generate some heat at 12V. There are two type of
power connector for the circuit, DC plug (J1) and 251002 (Power Connector). Normally AC to DC adaptor can
be plugged to J1 type connector.
The basic connection for In-Circuit Serial Programmer
(ICSP) is as displayed in Figure 5. There are a few
types of USB in-circuit programmer can be found in
Cytron, for example, UIC00B. However, programmer
is not included in this DIY project package since the
programmer can be reused for other projects.
For the instruction of using a PIC programmer, please
refer to the particular PIC programmer user’s manual at
cytron website.
Referring to Figure 3, the D2 is used to protect the circuit
from wrong polarity supply. C2 and C3 are used to
stabilize the voltage at the input side of the LM7805
voltage regulator, while the C1 and C4 are used to
stabilize the voltage at the output side of the LM7805
voltage supply. LED is a green color LED to indicate the
power status of the circuit. R1 is a resistor to protect LED
from excessive current that will burn the LED.
Created by Cytron Technologies Sdn. Bhd. – All Rights Reserved
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PR28 – Tic-Tac-Toe with mTouch
Transistor
HARDWARE
This project will require following hardware:
a.
b.
c.
d.
e.
f.
g.
h.
Figure 8
1 x PIC16F727
1 x PR28 Printed Circuit Board (PCB)
1 x LCD (2x16 character)
3 x 74HC595 Shift Register
9 x RGB LEDs
1 x piezo
1 x 9V-12V power supply
Related electronic components
The transistor is used to amplify the current for the RGB
LEDs. In this project, 3 NPN transistors, 2N2222A, are
used. The pin sequence is as shown in Figure 8. Beware
that wrong sequence will burn the transistor.
Please refer to Appendix A for the board layout of
PR28. The board layout is provided for free therefore
Cytron Technologies will not be responsible for any
further modification or improvement.
RGB LEDs
Interface LCD (2x 16 Character) with
PIC16F727
To use the LCD display, users have to solder 16 pin
header pin to the LCD display. LCD used in this
project is RT1602C, for other type of LCD, please
refer to its data sheet.
Figure 9
The RGB LED contains 3 LEDs encased in one shell. It
looks like a single white LED except that it has four
leads. It can be used to display 3 different colors which
are red, green or blue. Pin 1, pin 3 and pin 4 are the
anode pins for the red color LED, green color LED and
blue color LED, respectively. Pin 2 which has the longest
leg, is the cathode pin. In this project, pin 1, 3 and 4 are
connected to the 74HC595 shift register whereas pin 2 is
connected to the collector of a transistor.
In this project, RGB LEDs are used to show the output
for the Tic-Tac-Toe game where red color represents
player 1 and green color to indicate player 2. In addition,
if there is no winner in the game, blue color LEDs will
blink continuously.
Piezo
The piezo used in this project works similarly as a buzzer
except that it has no polarity. The difference of piezo and
buzzer is that piezo can play melody with the use of
PWM. Of course, before using PWM function, the piezo
needs to be connected to CCP1 or CCP2 pin of PIC
microcontroller. In this case, the piezo is connected to
RC2 which is CCP1. To play a certain note, we need to
adjust the PR2 value to get the PWM period needed by
using the equation below.
PWM period = [(PR2) +1] · 4·Tosc
To fully understand the working of the piezo, kindly refer
to the sample source code provided as well as the PIC
microcontroller datasheet.
Figure 11
Figure 11 is a 2X16 character LCD. LCD connection
pin and function of each pin is shown:
Pin
1
2
Name
VSS
VCC
3
VEE
4
RS
5
R/W
6
E
7
DB0
8
DB1
9
DB2
Created by Cytron Technologies Sdn. Bhd. – All Rights Reserved
Pin function
Ground
Positive supply
for LCD
Brightness adjust
Select
register,
select instruction
or data register
Select read or
write
Start data read or
write
Data bus pin
Data bus pin
Data bus pin
Connection
GND
5V
Connected to
a trimmer to
adjust LCD
brightness
RE0
GND
RE1
RB0
RB1
RB2
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PR28 – Tic-Tac-Toe with mTouch
10
11
12
13
14
15
DB3
DB4
DB5
DB6
DB7
LED+
Data bus pin
Data bus pin
Data bus pin
Data bus pin
Data bus pin
Backlight positive
input
16
LED-
Backlight
negative input
RB3
RB4
RB5
RB6
RB7
a resistor to
limit
excessive
current
GND
Figure 14
Figure 12
Interface 74HC595 with PIC16F727
The basic connection of 74HC595 is as demonstrated in
Figure 13 below.
Figure 15
Interface mTouch™ with PIC16F727
To utilize the capacitive sensing module in PIC16F727,
all the copper pads must be connected to the capacitive
channels of PIC microcontroller and set those pins to
analog pins. This step is very vital before proceeding to
software algorithm. In this project, the mTouch™ or
touch pad is connected as shown in Figure16.
Figure 13
As mentioned earlier, 74HC595 is a serial-in parallel- or
serial-out shift register. Basically, it works as
synchronous serial communication where one pin can be
pulsed up and down thereby communicating a data byte
to the register bit by bit. By pulsing second pin, the clock
pin, bits can be delineated. To have clearer picture on this,
please refer to Figure 14 and Figure 15, respectively.
Figure 16
Theoretically, to know whether the touch pad has been
touched or not is by determining the change of
capacitance. As demonstrated in Figure 17, before a
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PR28 – Tic-Tac-Toe with mTouch
finger presses the pad, the PCB pad itself has a
capacitance, Cp. However, if a finger presses the copper
pad, another capacitance, Cf is introduced where it is in
parallel with Cp. Thus, the equivalent of capacitance
increases after finger press. Additionally, the capacitance
change will result in change in frequency. To scan a pad,
frequency change on copper pad is measured. To get a
clear picture on this, please refer to Figure 17.
Not
Pressed
Figure 17
There are a few methods to perform capacitive sensing,
such as comparator, Charge Time Measurement Unit
(CTMU), Capacitive Voltage Divider (CVD) and
Capacitive Sensing Module (CSM). In this project, the
touch pad is sensed by capacitive sensing module (CSM)
at fixed time interval. The benefit of this method is that it
does not need external oscillator since the module has its
own oscillator embedded. The frequency of each pad at
rest is averaged.
Frequency Measurement
Since CSM is a frequency-based method, timer method is
used. Basically, Timer 2 is used as the timer resource
instead of using Timer 0 due to it has greater flexibility
in defining time base. On the other hand, Timer 1 gate is
used as a counter. It will increment at every rising edge
of capacitive sensing module output frequency. The
value on the Timer 1 will be a measure for CSM
oscillator frequency. The completion of Timer 1 gate
event, triggered by Timer 2 overflow, will generate a
Timer 1 gate interrupt. When servicing the interrupt, the
value from the Timer 1 can be read to determine the
oscillator frequency.
In detailed, capacitance of the pad alone results in a
corresponding square wave frequency. When the PR2
value is matched, the current count value in Timer 1 will
be read and stored as reference. Once the finger is
touched, the RC time constant of the oscillator increases
and thus results in a decrease of frequency of the square
wave output. Therefore, on the next interrupt, the Timer
1 value will be smaller. Using a software algorithm to
compare the difference between these values, the sensor
can be identified as pressed or not pressed. Below
explains the frequency changes graphically.
Not
Pressed
Pressed
Figure 18
For more detailed information on the working of
mTouch™, kindly refer to the application notes which
can be downloaded for free in Microchip website
(http://www.microchip.com)
Explanation
mTouch™
on
Tic-Tac-Toe
using
When a pad is touched, the frequency on the CSM
changes due to the extra capacitance from the finger.
The change in frequency is noted and the LEDs light
up to indicate which button was pressed. Since the
mTouch™ is used for the Tic-Tac-Toe game, the LEDs
will not light up immediately after the touch pad has
been pressed. Each copper pad is only responsible for
only one RGB LED. For example, a touch pad which is
noted as X1 is responsible to the RGB LED that is also
noted as X1. When that particular touch pad has been
pressed and being detected by PIC microcontroller,
PIC will check whether that particular pad has been
touched previously or not. If yes, that particular RGB
LED will not response. On the contrary, the RGB LED
will light up.
PCB circuit board
2
3
1
4
7
6
5
12
9
8
10
13
11
14
15
16
19
17
18
Components:
1.
2.
3.
Created by Cytron Technologies Sdn. Bhd. – All Rights Reserved
Slide Switch ( to ON or OFF the circuit)
2510-02 connector ( to use either 9V or 12V
battery)
AC-DC adaptor socket
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PR28 – Tic-Tac-Toe with mTouch
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
IN 4007 diode ( to protect the circuit from
wrong polarity)
LM7805 (to supply 5V for PIC and 74HC595
Shift register.
ICSP programmer connector ( to program the
code into PIC)
74HC595 shift register ( to control RGB LEDs)
Reset button ( to reset the PIC)
LED ( power indicator)
1N4148 ( to protect LED from wrong polarity)
Capacitors ( to stabilize both input and output
voltage of LM7805)
2N2222 transistors ( to amplify the current for
RGB LEDs)
RGB LEDs
Piezo ( to play melody)
PIC 16F727 ( the main brain of this project)
Contrast ( to control the contrast of LCD)
mTouch™ (for Tic Tac Toe gaming)
LCD ( to display the result and guidelines of the
Tic Tac Toe game)
0.1uF capacitor ( to stabilize the supply voltage
to the PIC)
Flow
chart
Measurement
for
ISR:
Frequency
ISR
Read Timer 1 value
Current
Reading <
(average –
threshold)?
Yes
No
Button not
pressed
Button pressed
Software: Flow Chart for main loop
Start
Perform average
Initialize PIC, LCD
And Capacitive Sensing
Module
Set Next Channel
Clear all variables
and set flag = 0
Restart Timer
Enable interrupt
Return
Timer 1
gate
interrupt?
Yes
No
Service interrupt
Main loop
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PR28 – Tic-Tac-Toe with mTouch
Flow chart for Tic-Tac-Toe Game
Main loop
Play starting melody
Check flag
Flag = 0?
No
Yes
Player 1
The button
pressed has been
pressed
previously?
No
Player 2
Yes
Toggle flag
Store ‘X’ or ‘O’ into
matrix based on flag
Display RGB LEDs
accordingly
Winner?
Yes
No
Yes
Draw?
Play melody
No
Toggle flag
Display result on LCD
Stop
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PR28 – Tic-Tac-Toe with mTouch
For more information about the software for this
system, please refer to the source code provided. The
explanation of each instruction is provided in the
source code as the comment of each line.
Guide for making 2510-02 connector
1
2
3
4
5
6
The source code is provided free and Cytron
Technologies will not be responsible for any further
modification or improvement.
GETTING START
User can obtain the hardware set for this project (PR28)
either by online purchasing (www.cytron.com.my) or
by purchasing it in Cytron Technologies Shop.
1.
Once user has the hardware set, soldering
process can be started. Please solder the
electronic components one by one according
to the symbols or overlays on the Printed
Circuit Board (PCB). Ensure that the
component value and polarity is correctly
soldered. Please refer to PCB Layout in
Appendix A.
Caution: Make sure all the connectors (2510) are
soldered in proper side. Those electronic
components have polarity such as capacitors,
diodes, PIC, 74HC595s, LM7805, transistors,
RGB LEDs and LED should be soldered in
right polarity or it may cause the circuit board
fail to work.
Warning: Before the battery (Power) is plugged in,
make sure the polarity is correct to prevent
explosion. Wrong polarity of capacitor also
may cause explosion.
7
Figure 19
Guide for making 2510-02 for
9V battery connector:
Figure 20 (not included in DIY project set)
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PR28 – Tic-Tac-Toe with mTouch
2.
Please download the necessary files and
document from Cytron Technologies website.
These included documentation, sample source
code, schematic, component list and software.
3.
The next step is to install MPLAB IDE and
HI-TECC C PRO into a computer. The
MPLAB IDE and HI-TECC C PRO can be
downloaded from www.cytron.com.my .
Please refer MPLAB IDE installation step
document to install the software. The
documents can be used to any version of
MPLAB IDE software.
4.
After the installation complete, open the
project file provided using MPLAB IDE.
Please refer MPLAB Open Project document
to open the sample program.
5.
Plug in power supply for the circuit. User can
choose to use battery or AD to DC adaptor.
AC to DC adaptor:
the power. The programmer is not included in
the hardware set but it can be found at Cytron
website. (User manual is provided at website).
7.
Test the functionality of the PCB board.
8.
Have fun!
TEST METHOD
1.
Switch ON the power
• Power LED (Green) will turn ON.
• A short melody will be played.
• LCD will show “Cytron Technologies
Sdn Bhd” and “PR 28 –Tic-Tac-Toe with
mTouch”).
• Then, LCD will show the indicator for
RGB LEDs, which is “Player 1 = red”
and “Player 2 = green”.
• Next, LCD will show “Player 1 starts
first”.
2.
Press your finger on the touch pad
• Tic Tac Toe game has been started.
• RGB LED will turn ON accordingly with
the position.
• For player 1, the RGB LED will be in red
color.
• Whereas, player 2 is in green color.
• LCD will guide user who is the turn each
time.
• Repeat this step continuously until there
is a winner.
If player 1 is a winner
• A melody will be played.
• LCD will display “Congratulation!!
**Player 1 win**”
If player 2 is a winner
• A melody will be played.
• LCD will display “Congratulation!!
**Player 2 win**”
If there is a draw
• Different melody will be played.
• LCD will display “Congratulation!!
**draw**” and blink continuously.
• All RGB LEDs will be blinking
continuously in blue color.
If all steps mentioned above can be executed,
your project is done successfully.
Congratulations!!
3.
Figure 21 (Not included in DIY project set)
4.
Connection to the PCB board:
5.
12V
Polarity
Figure 22
6.
Build the project and load the hex file into the
PIC microcontroller using the USB In-Circuit
Programmer (UIC00B). When user builds the
project, MPLAB IDE will generate hex file.
The hex file generated from MPLAB IDE will
be named according to project name, not C
file name. Cytron Technologies also provide
hex file for user. Do not forget to switch ON
6.
•
Please note that do not try to press more than
one touch pad each time as it will cause
instability of the system.
WARRANTY
No warranty will be provided as this is DIY project.
Thus, user is advised to check the polarity of each
electronic component before soldering it to board.
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PR28 – Tic-Tac-Toe with mTouch
Demonstration
1.
When player 1 press position Z1 on the touch pad, the RGB LED on position Z1 will turn ON in red color. The
LCD will show that player 2 is the next turn. This step is as shown in Figure below.
2.
Next, when player 2 press position Y2 at touch pad, the RGB LED on position Y2 will turn ON in green color.
The LCD will then guide users that player 1 is the next turn.
3.
These two steps will repeat till there is a winner or draw.
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PR28 – Tic-Tac-Toe with mTouch
Appendix A
PCB Layout:
1N4007
PWR
74HC595
ICSP
Adaptor
Slide
Programmer
Switch
LM7805
2N2222 Transistors
1N4148
Reset
330
0.1uF
1K
LED
1K
4K7 16V 10uF
100
PIEZO
74HC595
74HC595
RGB LEDS
PIC 16F727
0.1 uF
Contrast
mTouch™
LCD
* Cytron Technologies reserved the right to replace the component in the list with component of the same functionality
without prior notice.
Created by Cytron Technologies Sdn. Bhd. – All Rights Reserved
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PR28-Tic-Tac-Toe with mTouch
Prepared by
Cytron Technologies Sdn. Bhd.
19, Jalan Kebudayaan 1A,
Taman Universiti,
81300 Skudai,
Johor, Malaysia.
Tel:
Fax:
+607-521 3178
+607-521 1861
URL: www.cytron.com.my
Email: [email protected]
[email protected]
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13