JUL29
Decoding 4x4 keypad with AVR and 74C922
Keypad decoding or scanning using microcontroller is, lets face it - nothing new. The thing is that sometimes it can be a real pain when smaller microcontroller with not enough I/O pins is being used or when microcontroller has some more important task to do besides scanning the keypad.
Anyway, here is a project that scans 4x4 keypad using Atmel's 4+4 I/O pins (the usual method) and by using a special IC designed for that purpose: MM74C922. This IC is directly connected to keypad rows and columns with it's 4+4=8 pins, and on it's 4 digital output BCD pins it provides information about which key is pressed on keypad. Along with those 4 data pins it also has IRQ pin that can generate interrupt in microcontroller when key press is detected. Keypad scanning has never been easier!
© nevdull
[ Source: nevdull ]
similar content
- AVR programmer v1 (06-02-2006) [@Schematics/Microcontrollers]
- AVR tutorial - External Interrupts (13-09-2010) [@News]
- Hackvision retro game platform based on AVR (25-10-2010) [@News]
- AVR tutorial - IO registers (01-07-2010) [@News]
- AVR development board - update (11-01-2010) [@News]
- Huge AVR development board (18-09-2009) [@News]
- DTMF decoding and generation (05-03-2004) [@Schematics/Everything else]
- IR remote decoding (24-12-2008) [@News]
- Nokia 3310 AVR library (07-07-2010) [@News]
- AVR programmer v3 (15-02-2006) [@Schematics/Microcontrollers]
add comment
Please log-in!
You can log-in on forum link: Login page. After logging-in, return to this page and click refresh in your browser.