MIKROE-972 mikroElektronika, MIKROE-972 Datasheet - Page 33

• Manufacturer Part Number: MIKROE-972
• Description: Development Boards & Kits - ARM EASYMX PRO v7 ARM STELLARIS CORTEX-M3
• Manufacturer: mikroElektronika

Specifications of MIKROE-972

• Rohs: yes
• Product: Development Boards
• Tool Is For Evaluation Of: LM3S9B95
• Core: ARM Cortex M3
• Interface Type: CAN, I2C, SPI
• Operating Supply Voltage: 7 VAC to 23 VAC, 9 VDC to 32 VDC

SW12
SW12
EasyMx PRO
Piezoelectricity is the charge which accumulates in
certain solid materials in response to mechanical pressure,
but also providing the charge to the piezo electric material
causes it to physically deform. One of the most widely used
applications of piezoelectricity is the production of sound
generators, called piezo buzzers. Piezo buzzer is an electric
component that comes in different shapes and sizes, which
can be used to create sound waves when provided with
analog electrical signal. EasyMx PRO
comes with piezo buzzer which can be connected to PA6
microcontroller pin. Connection is established using SW12.1
DIP switch. Buzzer is driven by transistor Q2 (Figure 19-1).
Microcontrollers can create sound by generating a PWM
(Pulse Width Modulated) signal – a square wave signal,
which is nothing more than a sequence of logic zeros and
Piezo Buzzer
Freq = 3kHz, Duty Cycle = 50%
Freq = 3kHz, Duty Cycle = 80%
Freq = 3kHz, Duty Cycle = 20%
BUZZER
BUZZER
BUZZER
Figure 19-1: Piezo
buzzer connected to PA6
microcontroller pin
DATA BUS
R52
10K
R52
10K
R52
10K
R50
1K
R50
1K
R50
1K
VCC-5V
VCC-5V
VCC-5V
v7
PZ1
BUZZER
PZ1
BUZZER
BUZZER
PZ1
Q2
BC846
Q2
BC846
Q2
BC846
PERSPECTIVE
PERSPECTIVE
PERSPECTIVE
™
VIEW
VIEW
VIEW
VIEW
VIEW
VIEW
TOP
TOP
v7 for Stellaris
TOP
Freq = 3kHz,
Volume = 50%
Freq = 3kHz,
Volume = 80%
Freq = 3kHz,
Volume = 20%
PA6
®
SW12
ones. Frequency of the square signal determines
the pitch of the generated sound, and duty cycle of
the signal can be used to increase or decrease the
volume in the range from 0% to 100% of the duty
cycle. You can generate PWM signal using hardware
capture-compare module, which is usually available in
most microcontrollers, or by writing a custom software
which emulates the desired signal waveform.
Supported sound frequencies
Piezo buzzer’s resonant frequency (where you can expect
it's best performance) is 3.8kHz, but you can also use it to
create sound in the range between 2kHz and 4kHz.
How to make it sing?
Buzzer starts "singing" when you provide
PWM signal from the microcontroller
to the buzzer driver. The pitch of the
sound is determined by the frequency,
and amplitude is determined by the
duty cycle of the PWM signal.
BUZZER
R52
10K
R50
1K
VCC-5V
PZ1
BUZZER
Q2
BC846
PERSPECTIVE
VIEW
VIEW
TOP
Enabling Piezo Buzzer
In order to use the on-board Piezo Buzzer in
your application, you first have to connect the
transistor driver of piezo buzzer to the appropriate
microcontroller pin. This is done using SW12.1 DIP
switch which connects it to PA6 pin.
Figure 19-2:
push
SW12.1 to
ON position
to connect
Piezo buzzer
to PA6
page 33