2x2 Key click
1
2x2 Key click
2x2 Key click
2x2 Key click
IC/Module
Interface
SN74HC14 datasheet
[1]
74HC32 datasheet
[2]
AN, RST, CS, PWM, INT
Power supply 3.3V or 5V
Product page 2x2 Key click [3]
Schematic
2x2 Key click schematic
[4]
2x2 Key click has a 4 PCB button keypad. It carries the SN74HC14 Hex Schmitt-Trigger Inverter from Texas
Instruments and 74HC32 quad 2-input OR gate from NXP. The click allows multiple key presses and is designed to
use either 3.3V or 5V power supply.
The silkscreen markings on the click let you know which button is which. The buttons that can be independently
read.
Features and usage notes
The debounce circuit
In electronics, two metal components tend to bounce or create multiple signals when they are in contact with each
other, like when you push a button before they get to a stable state. You want a single contact to be recorded, but the
microcontroller records this as if you pressed the button many times.
So debouncing is, as the name states, the removal of bounces or spikes of low and high voltages. Graphically
speaking, you want a clean line, not spikes. A debounce circuit makes sure that there are no voltage changes on the
output.
2x2 Key click
2
Interrupt service routine
All four Schmitt-trigger outputs are connected to input pins of the logic OR gate 74HC32, whose output is directly
connected to the INT pin on mikroBUS. This pin is used to signalize an interrupt to the MCU any time a button is
pressed.
In this way, the MCU software can be implemented as a simple polling routine, without any delays programmed in
the code, like it would be necessary if there wasn’t a hardware debouncing circuit present.
Thanks to the INT pin you can easily program a common interrupt service routine, in order to detect when a button is
pressed (the state of the button changes from low to high logic level).
Key features
• 74HC32 quad 2-input OR gate
• High noise immunity
• Low power dissipation
• SN74HC14 Hex Schmitt-Trigger Inverter
• Outputs Can Drive Up to 10 LSTTL Loads
• Low Power Consumption, 20-μA Max ICC
• 4 black PCB buttons onboard
• Interface: PWM, INT, AN, RST, CS pins
• Runs on either 3.3V or 5V power supply
Additional information
• J2 is the interrupt enable pin (by default it is in the enable status).
• J1 is the power selection pin.
Pinout diagram
This table shows how the pinout on 2x2 Key click corresponds to the pinout on the mikroBUS™ socket (the latter
shown in the two middle columns).
Notes
Pin
Pin
Notes
mikroBUStm
When button T1 is pressed the pin is
active
T1-OUT 1 AN
X PWM 16 T4-OUT When button T4 is pressed the pin is active
When button T2 is pressed the pin is
active
T2-OUT 2 RST
INT
15 TINT
When button T3 is pressed the pin is
active
T3-OUT 3 CS
TX
14 NC
NC
4 SCK
RX
13 NC
NC
5 MISO
SCL
12 NC
NC
6 MOSI
SDA
11 NC
Power supply
+3.3V
7 +3.3V
+5V
10 +5V
Ground
GND
8 GND
GND 9
GND
Interrupt pin that notifies the MCU that a button is
pressed
Power supply
Ground
2x2 Key click
3
Programming
The demo initialises the TFT display and sets pins to operate in input direction. The main fucntion of the demo uses
the polling method to check if inputs are on an active level. The TFT display shows the button state according to
detect level.
void main()
{
system_init();
Draw_Taster(X1,
Draw_Taster(X2,
Draw_Taster(X1,
Draw_Taster(X2,
Y1,
Y1,
Y2,
Y2,
RELEASED,
RELEASED,
RELEASED,
RELEASED,
"T1");
"T2");
"T3");
"T4");
while(1)
{
if(Taster_Pressed(TAST1, &t1_state))
Draw_Taster(X1, Y1, PRESSED, "T1");
if(Taster_Released(TAST1, &t1_state))
Draw_Taster(X1, Y1, RELEASED, "T1");
if(Taster_Pressed(TAST2, &t2_state))
Draw_Taster(X2, Y1, PRESSED, "T2");
if(Taster_Released(TAST2, &t2_state))
Draw_Taster(X2, Y1, RELEASED, "T2");
if(Taster_Pressed(TAST3, &t3_state))
Draw_Taster(X1, Y2, PRESSED, "T3");
if(Taster_Released(TAST3, &t3_state))
Draw_Taster(X1, Y2, RELEASED, "T3");
if(Taster_Pressed(TAST4, &t4_state))
Draw_Taster(X2, Y2, PRESSED, "T4");
if(Taster_Released(TAST4, &t4_state))
Draw_Taster(X2, Y2, RELEASED, "T4");
t1_state
t2_state
t3_state
t4_state
=
=
=
=
TAST1;
TAST2;
TAST3;
TAST4;
Delay_ms(POLLING_PERIOD);
}
2x2 Key click
}
Resources
•
•
•
•
•
SN74HC14 datasheet [1]
74HC32 datasheet [2]
Demo code / Library [5]
2x2 Key click schematic [4]
mikroBUS™ standard specifications [6]
References
[1]
[2]
[3]
[4]
[5]
[6]
http:/ / www. ti. com/ lit/ ds/ symlink/ sn74hc14. pdf
http:/ / www. nxp. com/ documents/ data_sheet/ 74HC_HCT32. pdf
http:/ / www. mikroe. com/ click/ 2x2-key/
http:/ / cdn-docs. mikroe. com/ images/ 7/ 7d/ 2x2-Key. pdf
https:/ / libstock. mikroe. com/ projects/ view/ 1965/ 2x2-key-click
http:/ / www. mikroe. com/ mikrobus/
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Article Sources and Contributors
Article Sources and Contributors
2x2 Key click Source: http://docs.mikroe.com/index.php?oldid=2680 Contributors: Lana.vulic
Image Sources, Licenses and Contributors
File:2x2-key-click.jpg Source: http://docs.mikroe.com/index.php?title=File:2x2-key-click.jpg License: unknown Contributors: Lana.vulic
File:mikrobus logo.png Source: http://docs.mikroe.com/index.php?title=File:Mikrobus_logo.png License: unknown Contributors: Vojislav.gvozdic
License
Creative Commons Attribution
https:/ / creativecommons. org/ licenses/ by/ 4. 0/
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