Keypad programming for arduino

Projects Programming
1

Hi, i heard that you can write the code of keypad to arduino using analog input, may i know how this done? and if there are any examples that i can use?

2

Sure, you make a string of resistors from +5 to ground. Attach the middle of the string to an analog input.
Then, grounding the junction of 2 resistors one at a time will change the analog voltage read in. You poll the analog input and when you see change from the non-button push reading you know a button was pushed.

There was a great example of this from a fellow in Spain in the old forum.
You may have luck searching for Spanish analog button or similar.
Maybe one button keypad.

3

I found this link that might be helpfull: http://www.instructables.com/id/Arduino-3-wire-Matrix-Keypad/

I really dont know, but would like to, if the values of the resistors can be changed and how do you calculate them.
Regards

4

String ten 1K resistors in series from 5V to Gnd, R10 to R1, R10 at 5V and R1 at Gnd.
Connect the junction of R9 & R10 (call this spot J9) to an analog input.
J1 = junction of R1/R2. Each Jx will be a button going to ground.
J2 = junction of R2/R3, etc.

Now you have a simple voltage divider where Vout = R2/(R1+R2),with R2 being the resistors between J9 and Gnd, and R1 being the Resistor above J9.
You can then make a simple excel spreadsheet that will calculate the voltage J9.

With no buttons pressed, J9 = 5*(R1+R2+R3+R4+R5+R6+R7+R8+R9)/* ((R1+R2+R3+R4+R5+R6+R7+R8+R9)+R10) )
more simply written as 5*sum(R1:R9)/sum(R1:R10)

With J9 pressed, J9 = 0V
With J8 pressed, J9 = 5*(R9)/(R9+R10)
J7 pressed, J9 = 5sum(R8:R9)/sum(R8:R10)
J6 pressed, J9 = 5sum(R7:R9)/sum(R7:R10)
J5 pressed, J9 = 5sum(R6:R9)/sum(R6:R10)
J4 pressed, J9 = 5sum(R5:R9)/sum(R5:R10)
J3 pressed, J9 = 5sum(R4:R9)/sum(R4:R10)
J2 pressed, J9 = 5sum(R3:R9)/sum(R3:R10)
J1 pressed, J9 = 5*sum(R2:R9)/sum(R2:R10)

With 1K resistors, values should be:
J9 pressed = 0
J9 open = 4.5V
J8, 2.5
J7, 3.333333333
J6, 3.75
J5, 4
J4, 4.166666667
J3, 4.285714286
J2, 4.375
J1, 4.444444444

With the excel spreadsheet, you can play with different values easily and see if you can find a spread that you like better.

5

Example & spreadsheet to go with the above.
http://www.crossroadsfencing.com/keypad_divider.xls