2×2 Key click

Name: 2x2 Key click
SKU: MIKROE-2152
Price: 180.00 ZAR
Availability: BackOrder

R180.00 ex. VAT

2×2 Key click has a 4 button keypad.

The click allows multiple key presses and has a debounce circuit composed of 74HC32 quad 2-input OR gate from NXP and the SN74HC14 Hex Schmitt-Trigger Inverter from Texas Instruments. 2×2 Key click is designed to use either 3.3V or 5V power supply. The buttons can be independently read.

Stock: Lead-time applicable.

R171.00

10+

R162.00

15+

R153.00

20+

R147.24

SKU: MIKROE-2152 Categories: HMI, MikroElektronika

Description
Additional information

2×2 Key click has a 4 button keypad. The click allows multiple key presses and has a debounce circuit composed of 74HC32 quad 2-input OR gate from NXP and the SN74HC14 Hex Schmitt-Trigger Inverter from Texas Instruments. 2×2 Key click is designed to use either 3.3V or 5V power supply. The buttons can be independently read.

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. Thanks to it, one button press is recorded as such.

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).

Specifications

Type	Pushbutton/Switches
Applications	Human machine interface applications
On-board modules	74HC32 quad 2-input OR gate from NXP and the SN74HC14 Hex Schmitt-Trigger Inverter from Texas Instruments
Key Features	74HC32 quad 2-input OR gate, SN74HC14 Hex Schmitt-Trigger Inverte
Interface	GPIO
Compatibility	mikroBUS
Click board size	M (42.9 x 25.4 mm)
Input Voltage	3.3V or 5V

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 2×2 Key click corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
When button T1 is pressed the pin is active	T1-OUT	1	AN	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	Interrupt pin that notifies the MCU that a button is pressed
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	Power supply
Ground	GND	8	GND	GND	9	GND	Ground

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.

 1 void main()
 2 {
 3     system_init();
 4 
 5     Draw_Taster(X1, Y1, RELEASED, "T1");
 6     Draw_Taster(X2, Y1, RELEASED, "T2");
 7     Draw_Taster(X1, Y2, RELEASED, "T3");
 8     Draw_Taster(X2, Y2, RELEASED, "T4");
 9 
10     while(1)
11     {
12         if(Taster_Pressed(TAST1, &t1_state))
13             Draw_Taster(X1, Y1, PRESSED, "T1");
14 
15         if(Taster_Released(TAST1, &t1_state))
16             Draw_Taster(X1, Y1, RELEASED, "T1");
17             
18         if(Taster_Pressed(TAST2, &t2_state))
19             Draw_Taster(X2, Y1, PRESSED, "T2");
20 
21         if(Taster_Released(TAST2, &t2_state))
22             Draw_Taster(X2, Y1, RELEASED, "T2");
23             
24         if(Taster_Pressed(TAST3, &t3_state))
25             Draw_Taster(X1, Y2, PRESSED, "T3");
26 
27         if(Taster_Released(TAST3, &t3_state))
28             Draw_Taster(X1, Y2, RELEASED, "T3");
29             
30         if(Taster_Pressed(TAST4, &t4_state))
31             Draw_Taster(X2, Y2, PRESSED, "T4");
32 
33         if(Taster_Released(TAST4, &t4_state))
34             Draw_Taster(X2, Y2, RELEASED, "T4");
35             
36         t1_state = TAST1;
37         t2_state = TAST2;
38         t3_state = TAST3;
39         t4_state = TAST4;
40             
41         Delay_ms(POLLING_PERIOD);
42     }
43 }