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Hi,

I am afraid that I'm a newly registered member.
Indeed, the next question made me register and join your community.

I'm an electrical engineering student and I received an assignment from my professor.
I should make a 4x4 keypad and print out values on an LCDdisplay depending on the pushed button.

I have to make my own 4x4 keypad *** . The reason why is not of a huge importance.

I thought someone here could help me and explain me how does the existing 4x4keypad work.
I have to connect 1 row per 1pin so I couldn't come up with any idea how to detect which button was pushed exactly.

I am aware that my problem is more connected with logic than flowcode itself.



Thank you.

Hi eldarjah

Have you had a look at the e-block keypad datasheet. It has a full circuit and shows how the switches are wired.
That way you could make one from conventional push switchs and some resistors.

Simply, when a switch is pushed it joins two of the lines three vertical ie down from 1 2 3 and four horizonal through 1 4 7 *
The pic detects which 2 lines are connected

Hope Ive explained it simply, bit early in the morning & just got to work.

If you can use flowcode, a home brew pad should still work ok.

Hi,

eldarjah wrote:I should make a 4x4 keypad and print out values on an LCDdisplay depending on the pushed button.

As john said you can have a look first at the following link...
http://www.matrixmultimedia.com/resourc ... 4-30-1.pdf
It will give you idea how to make 4*3 keypad which you can modify to 4*4..
All the programming resources also in the following link..
http://www.matrixmultimedia.com/product ... PHPSESSID=
Have a look n start and let us know how are you getting into that..
Enamul

I thought someone here could help me and explain me how does the existing 4x4keypad work.
I have to connect 1 row per 1pin so I couldn't come up with any idea how to detect which button was pushed exactly.

Well it is quite easy.

I will try to explain to you how it works.
Take the datasheet from the eblock with the Keypad.
http://www.matrixmultimedia.com/resourc ... 4-30-1.pdf

its all about scanning Colum's and Rows. If you apply 5V on R1:A and you press key 1 then you know that whatever is connected to that pin A you just know that Key 1 is pressed.
However you cannot connect R1:A & R1:B & R1:C to 5V, if you do this you cannot tell if you pressed key 1, key 2 or key 3.

So to interface the Keypad to a PIC, AVR, ARM you would need at least for a 4x3 keypad, 7 I/O available.
For a 4x4 keypad you would need to have 8 I/O.

for a 4x3 keypad connect 3 pins to the Rows and 4 pins to the columns.

I hope this helps you out, if not tell me what you don't understand and I will try to explain more in depth.

Regards Jordy