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Topic: Debounced Breadboard Keypad (Read 5772 times) previous topic - next topic

Debounced Breadboard Keypad

I've been getting tired of having to wire up buttons and paste in debounce code (or wire up debouncers for TTL projects) every time I want any kind of user input.

I was browsing around Maxim's site, when I stumbled upon the MAX6816-6818 series of button debouncers.  These are single, dual, and octal channel debouncers.  Attached is the design files for a simple eight-button breakout board for the MAX6818 designed to be plugged into a breadboard.  In addition to the eight active-low debounced outputs, the edge connector includes an active-low button-change interrupt, and an active low enable input, which can be optionally solder-jumpered on, if the button outputs don't need to be tri-stated.

I'm a little deep in trying to get my last batch of PCBs working, but I figured I'd release this now, untested.  A little late to be useful for the 7400 contest, unless you order the PCB right now.

Re: Debounced Breadboard Keypad

Reply #1
this could be very useful, thanks for posting it.


Re: Debounced Breadboard Keypad

Reply #3
that chip is like 10-15 USD, much cheaper alternative would be to get a 16 GPIO MC and do a simple debouncing algoritham, the cost of the chip would be around 1-2 USD.
best regards FIlip.

Re: Debounced Breadboard Keypad

Reply #4
I'v seen it yesterday for 3.4$ .. that's way below 10-15$ ... I might missed the min order quantity ... if they are 10+ for 10pcs then yes, I'd rather stay with RC+74HC14

Re: Debounced Breadboard Keypad

Reply #5
my coment was based on farnell pricing, at digi key they are 8.6 usd a peace, withc is more then a spartan 3a FPGA witch could probably debounce a full pc keyboard
best regards FIlip.

Re: Debounced Breadboard Keypad

Reply #6
A friend yesterday told me he can source then per piece for under 4$ (in usa, no idea what store will ask him) ... but yes, farnell show them to cost more then 10GBP

Re: Debounced Breadboard Keypad

Reply #7
Damn.  I agree; that pricing is kind of a problem.  I hadn't bothered looking, since I just sampled two of them.  Maybe I'll respin it using a 7414 and only 6 buttons...  It'll just be kind of too bad losing the !CH functionality.  I thought that was pretty slick.

Re: Debounced Breadboard Keypad

Reply #8
I think the MAX6818 (octal of the serie) is a bit expensive (arround 6,5 euros in small qtt, and arround 3,8 euros for big qtt). While it has nice volatage range carachteristics, it can be easily replaced by a 1 euros MCU (any pic16fxx or pic18xx could do it), and you have the software control of things if you want to read an inverted entry or to send back data via I2C, SPI, OW or any protocol you want.
You can make such chip once and use it multiple times as you are going to do with MAX6818.
You can also do that with PIC10Fxx for small factor stuff.

Re: Debounced Breadboard Keypad

Reply #9
are those little square buttons available in  a config like
when release it closes one pole and when push close the other pole ?
:-)