Post by thread:[OT] 4x4 Hex Keypad

Hello! I have an hex keypad with 16 pins (one for each key) and 1 common. Can I use this type of keypad in a project that requires a 4x4 matrix keypad (8 lines/pins)(row/column selection)? How can I do that? Sorry for my ignorance. And thank you for your time. Special thanks to those people that always find the time and knowledge to answer my questions. I owe them... ------------------------------------ netQ <spam_OUTnetquakeTakeThisOuTinnocent.com> http://virtuaweb.com/picprog "Home of amateur PIC programmers..." -----BEGIN PGP PUBLIC KEY BLOCK----- Version: 2.6.2 mQCNAzV38BkAAAEEALfWv9j3f+tZ+z2IW+2o9Ebx4bUGnHjHPqIe0a6yVKawaeV/ Y4I6L2/A0ddbVMG8+qJ0MvHNkr3DzYkpW+hTl9zAzXkKBdZ3GA5bbvot7entl/O2 YDtRWUV730koxBo5iFFUbJH5kbmkox+h3znj34zPnZNWzNaqOAwol3wABfBNAAUT tBxOZXRRIDxuZXRxdWFrZUBpbm5vY2VudC5jb20+ =0bVU -----END PGP PUBLIC KEY BLOCK-----

German wrote: > I have a hex keypad with 16 pins (one for each key) and 1 common. > Can I use this type of keypad in a project that requires a 4x4 matrix > keypad (8 lines/pins)(row/column selection)? Yes, but you aren't going to like the answer! You'll need four 4066 chips and two octal SIL resistor packs for pull-downs. Each key and pull-down controls one "switch" which makes the matching matrix closure. This *is* very useful if you need for example, to control a remote control (IR) sender to control some device for four functions, and there is a cute trick using a pocket calculator as a dirt-cheap item counter. The message for your application however is - you need a matrix keyboard and they are usually inexpensive and common. Note that some keyboards (real old Touch-Tone telephone pads) have a common with rows and columns. In that case of course, you don't need to use the common and it would do the job. -- Cheers, Paul B.

"Paul B. Webster VK2BZC" wrote: > > Hello Tony. > > > Maybe a 74C150 16 line to 1 line multiplexer. > > Now how would you use that? > I could be wrong (it's been a long day) but I thought you could set a 4 bit code to sample any one of the 16 inputs. There are inverted, but that doesn't matter. If a key is pressed on the input line that corresponds to the 4 bit data, then the output state will be opposite of the key state. 6 lines from a PIC including the strobe. -- Best regards Tony http://www.picnpoke.com Email salesKILLspampicnpoke.com

No you can't I do not think it is economical to reserve 16 I/O for keypad. Andre > I have an hex keypad with 16 pins (one for each key) and 1 common. > Can I use this type of keypad in a project that requires a 4x4 matrix > keypad (8 lines/pins)(row/column selection)? > How can I do that? >

No easy way to make it work with that project as-is, but could conceivably read such a keypad with a 16c7x series pic using some resistors and an a/d input. Simultaneous keypresses would confuse it though, and false readings would be possible when the voltage is changing, depending on what resistor values are chosen and how much capacitance is present. This would have to be dealt with in software. Not the prettiest solution, but it does have the advantage of consuming only one pin on the pic. > I have an hex keypad with 16 pins (one for each key) and 1 common. > Can I use this type of keypad in a project that requires a 4x4 matrix > keypad (8 lines/pins)(row/column selection)? > How can I do that? --- Peace, William Kitchen .....billKILLspam.....iglobal.net The future is ours to create.