Summary of 4X4 Keypad Interfacing with ATmega32 and LED Display
This article details interfacing a 4x4 matrix keypad with an AVR ATmega32 microcontroller to display pressed key values on a 1x8 LED array. The system continuously scans the keypad rows and columns via the `read_keypad` function. When a key is detected, its specific value is shown; otherwise, the last pressed value remains displayed.
Parts used in the Keypad Interfacing Project:
- AVR ATmega32 microcontroller
- 4X4 matrix keypad
- 1X8 LED array
Keypads are parts of HMI or Human Machine Interface and play really important role in a small embedded system where human interaction or human input is needed. Matrix keypads are well known for their simple architecture and ease of interfacing.
In this project, we will learn How to interface a 4X4 keypad with AVR ATmega32 microcontroller. Here, we will display the value of the pressed key in a 1X8 LED array. See the below table to know the value assigned to each key of the 4X4 keypad. For to display the value of the pressed key, the microcontroller should know if any key is pressed or not and if pressed then which key is pressed. To know all this, the microcontroller scans each row or column of the 4X4 keypad one by one continuously (scanning is done by the read_keypad function). When any key of 4X4 keypad is pressed, the read_keypad function returns the value of the pressed key and the microcontroller displays it in the 1X8 LED array. When none of the key is pressed the read_keypad function returns 0XFF and the 1X8 LED array displays the value of the last pressed key. Now, press different keys of the 4×4 keypad and see the output in the 1X8 LED array.
| Key Pressed | Key Value |
| 1 | 1 |
| 2 | 2 |
| 3 | 3 |
| 4 | 4 |
| 5 | 5 |
| 6 | 6 |
| 7 | 7 |
| 8 | 8 |
| 9 | 9 |
| 0 | 0 |
| * | 10 |
| # | 11 |
| A | 12 |
| B | 13 |
| C | 14 |
| D | 15 |
Softwares Required
For more detail: 4X4 Keypad Interfacing with ATmega32 and LED Display
- What is the primary purpose of this project?
To interface a 4X4 keypad with an AVR ATmega32 microcontroller and display the pressed key value on a 1X8 LED array. - How does the microcontroller detect which key is pressed?
The microcontroller scans each row or column of the 4X4 keypad one by one continuously using the read_keypad function. - What value does the read_keypad function return when no key is pressed?
When none of the keys are pressed, the function returns 0XFF. - What happens to the LED display if no key is currently pressed?
The 1X8 LED array displays the value of the last pressed key. - Which software tools are required for this project?
Required software includes AVR Studio 4, WinAVR 2010, SinaProg Hex Downloader, and USBasp Driver. - What value is assigned to the asterisk (*) key?
The asterisk key is assigned the value 10. - Does the project use a standard matrix keypad architecture?
Yes, it uses a well-known simple matrix architecture for ease of interfacing.
