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34 Threads found on edaboard.com: 74c922
Hi, You must connect two external capacitors, one on Osc pin and the other to Keybounce Mask pin. See the datasheet page 5 for the values of Cosc (connected to Osc pin) and Ckbm (connected to Keybounce mask = t
hi here is the model for 74c922 made by loving james
can you chak this
hi friends, do anyone of u know how to interface pic+74c922+3*4(nightmare) because one of my friend urgently needs it.thanx
Just use the 74c922 and plain 4X4 keyboard, wire the keyboard to the X and Y inputs of the 922 , Wire the outputs of the 922 to AD0-AD3 in the 8051 , Map the 922 to an adress and then you have 2 options: A. Using interrupt for indicating that a key is pressed (Wire DA from the 922 to the INT1 in the 8051) - it will be a very good idea
Hey guys, I'm kinda stuck on this one. I'm trying to use a 3x4 keypad, which goes to a 74c922 IC. From the 74c922, I'm putting the data out to my PPI and the data available pin to my PIC. I can handle the coding part, but I just can't get the hardware part right. I've hooked it all up and when i press a key, I get 4 different codes for it. ke
Dear all, I like to use 74c922 keypad encoder to connect the keypad (3x4) to PIC18F452. I searched the forum for this topic. But, I could not able to find anything useful for me. I have connected the DA(Data available) pin at interrupt pin on the PIC. I can able to receive some character from the keyboard when the key is pressed. But, I don't kn
A keypad has 7 pins. A 74c922 has 18 pins. And I don't know, which pins of keypad I need to connect to pins of chip. Help me
Hello, I need a 3x3 keyboard for control a robor arm...i dont know if can use the IC 74c922. How I use it? Any idea? Thank You
Hi If you want easy complete solution you can use 74c922 or 74c923 (keyboard controller) Or make it in a small uc or cpld and (prog debounce filter for it). Best regards.
Hi Zelec, first take a look on the 74c922 from National Semiconductor from the data you can make your own keypad decoder on CPLD. If you use 4 bit mode for LCD you save a lot of CPLD resources. LCD intelligent displays need only 3 control signals R/W, E, RS. here is a link for the 74c922/923.pdf
Hi, See this app. note from IAR if you do not want to use 74c922 = t
Tip: Uses a 74c922, but well...
A 74c922 will do the job, but it might be expensive: /Rambo
The 74c922 or 923 does just that. It scans the keyboard matrix and puts up a Data Valid signal when a key is pressed. You can use this data valid to create an interrupt on your MCU and read the key through 4-5 bits. So the only thing u need from the MCU is 4-5 portpins and an interrupt. Ive used this before and although the 74C923 aint cheap ($10)
hello, you must try first to disect or testing the output of pin D1,D2,D3 if there is an equivalent digital combinations for the desired characters 1. say " R" try to test pins 17,16,15,13, for D's output 2. next say if you have proper capacitance in the debounce input 3. then also check the enable pin's out put after that ..if you
Take a look at 74c922 IC ( ). It is 16-key encoder .. Regards, IanP
Try 74c922: Regards, IanP
hi all, I'm looking for a keypad program in c that uses the 74c922 encoder chip. A 3x4 keypad is used. I'm really struggling with this. Can anyone help me? How do you wright the program so that the eprom can tell what keypad has been pressed according the encoder chip? i got some information,but still i have a confusion with it.i am shari
One option is to use the 74c922 keypad decoder and connect the DA (data available) pin to INT0 or INT1 .. Here is an example: Regards, IanP
Not that I am aware of .. There is Keypad IC, namely the 74c922, but it doesn't have serial port and has to be read by a microcontroller through 4-bit data + control signals port .. So, from that point of view option with PICAXE microcontroller can be very tempting .. Regards, IanP
hi i want to implement a keypad using PicBasic PRO, and i want to use the interrupt on change of PORTB. i am using 16F877 and i can't use "polling routine" in this project with , also i can't use any Keypad IC (like 74c922). i wrote a program and i attach its PROTEUS file its schematic. '**********************************************
well a hex keypad (4x4) will give you an 8bit code. though if you use a 74c922 decoder you effectively cut it down to 4bits (0 to 16)!!! though you need to connect the decoder to an interupt line. Its all pretty easy. no source code though, I discovered the beauty of C a few years back! Hope this helps
Here's MikroC code for a 4x8 keypad, for those who don't want to use specialize ic like 74c922. I derived this from CCS forum's flexible keypad ( for more info search for it on CCS forum). might be useful to some. I had to use 20Mhz crystal, less than that it doesn't work could it be because I use pic16f628 instead of pic16f628A? outpu
here is a code: . . . . . . const char key_table = "123A456B789C*0#D"; unsigned char key; //unsigned char ex0_isr_counter = 0; void ex0_isr (void) interrupt 0 { //ex0_isr_counter++; // Increment the count unsigned char keypad_scan; key = ((keypad_scan=keypad_address)&keypad_mask); key = key_table; goto
Keypad requires periodic sequential scanning and if you want to put the scanning microcontroller to sleep something else has to scan it (keypad) instead .. One option is to use dedicated keypad IC (with an interrupt) such as the MM74c922 .. Here is it's detailed description: Regards, IanP
Hi all, I use Pic16f877 with 4x4keypad.I cannot get the interrupt to work.I read the key OK, but then cannot prevent the code from scanning the same key again while the key is pressed.I tried to to keep it out by an IF statement, but then it only scans once when the program runs at startup?????? I use CCS C. Here is some of the code I t
Use the 74c922 keyboard decoder chip (with interupt line)
Please, I need the library of 74c922 key matrix component. Regards Frigo
Hello, We Need To Create This Simple 7 Button Joy-Pad, using any interface possible. Since I am a total noob in this stuff, can anyone help me with this ? I have heard ( maybe it's wrong ) that PS/2 interface would be the simplest. The JoyPad must contain these 7 keyboard keys : Up, Down, Left, Right, Enter, SpaceBar, Shift ( Right Shift ).
You have two options, either use a 74c922 to scan the keyoad for you and let it present the key number to the Z80 input port, or, you can connect the output port to the keypad columns and the input port to the keypad rows directly. If you use the second method, your Z80 software should make one, and only one, output pin to the keypad high at a time
Hello, When I'm trying to use the keypad with the 74922 chip it refers only to the first button I press and any other buttons don't work. When I'm starting the simulation I can see the chip scanning for presses but when I press it never continues. 79242 Thanks in advance
You are not really scanning the keys, just reading the output of the 74c922. As wp100 points out it is easy to do without an external interface but if you want to do it the way you show, this should be simpler: char key; if(PORTDbits.RD0 == 1) { key = PORTC & 0x0F; } Brian.
Hi all, I'm new to writing code I am trying to interface a 4 row by 3 column keypad to display which buttons are being pressed on the LCD and its being used in a security/password scenario. the LCD is a hitachi HD44780U I am using the C18 compiler on MPLAB and the microcontroller that has been assigned to me is the PIC18F4321 I was cons