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keypad 74c922
27 Threads found on 74c922
118929 I'm designing a board to multiplex 24 inputs to 1 pc104 port which is on my SBC. There are (3) '374's which are polled by the SBC using lines from pc104 port B (output) to see if one of the inputs has changed. The 4th '374 reads the output from a 74c922 keypad chip of which the DA pin is connected to an interrupt p
Use a 74c922 if you can find one - all done in one IC, including the debounce. Brian.
The high level like C langauge cann't access PC counter , So Assembly langauge is prefer to pre setup, I think so. Why you donn't use 74c922 encoder chip to link between 3x4 keypads and The PIC CHIP . Port scan like in PC Computer is make loosing time because Ex. we can gennerate table for change to the other langauge in the next time in memory
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.
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 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
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
You don't have to. The 74c922 does all that for you. All you need to do is monitor the "Data Available" signal on pin 13 and when it goes high, you read the data output lines. Each key produces a unique binary number on the output lines. Note that for the '922 to work you must have the -Output Enable (pin 14) held low or grounded. Brian.
Please, I need the library of 74c922 key matrix component. Regards Frigo
Use the 74c922 keyboard decoder chip (with interupt line)
Hello, Because I have only 3 columns, i grounded Y4 of the 74c922 Who told you to do? It can be easily seen from datasheet, that the part can't operate this way. As the idle state is all contacts open, just leave unused matrix pins unconnected! If you didn't forget to connect the oscillator capacitor, there's a good chance, that
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
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
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. '**********************************************
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
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
Try 74c922: Regards, IanP
Take a look at 74c922 IC ( ). It is 16-key encoder .. Regards, IanP
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)
hi friends, do anyone of u know how to interface pic+74c922+3*4(nightmare) because one of my friend urgently needs it.thanx
can you chak this
A 74c922 will do the job, but it might be expensive: /Rambo
hi here is the model for 74c922 made by loving james
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, See this app. note from IAR if you do not want to use 74c922 = t
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.
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