4x4 Keypad interfacing to PIC18f458

Hi,

i want to inetrface a 4x4 keypad to PIC18f458.

I am using the below circuit but my code is not working.



When i simulate in proteus it works but doesnot work in hardware.

Please help. If any c code is available, plz help with that also.

Thanks.

Hi csr1981,

How do you simulate using only a connector in place of the keypad? Please post your code so that we may help you.

hardware looks ok

Hi,
Keyboard connection
**broken link removed**

Hi,
In the circuit provided, you forgot to set MCLR pin high, so the microcontroller is in reset mode and not doing anything. Connect the MCLR pin to +5v with a resistor (about 10k) and try it.
Hope it helps.
Tahmid.

Hi Tahmid

i had just posted the part of my circuit. I have connected the MCLR pin to Vcc.
All other things are working fine.
Only the keypad is not working.

Hi,
Maybe you should pull-down RD0, RD1, RD2 and RD3 to ground with 10k resistors.
I do that when I use keypad.
Tahmid.

Tahmid said:

Hi,
Maybe you should pull-down RD0, RD1, RD2 and RD3 to ground with 10k resistors.
I do that when I use keypad.
Tahmid.

Click to expand...

You don't need any external resistors.
Its not necessary. (depends ur code.)

Can you help with c code.

Thanks

Hi,
I can help you if you can use mikroC.
Tahmid.

Hi Tahmid,

Yes no problem, i can use mikroC.
Also if you can share the hardware ckt.

Thanks.

csr1981 said:

Hi Tahmid,

Yes no problem, i can use mikroC.
Also if you can share the hardware ckt.

Thanks.

Click to expand...

If u have CCS compiler use the example program with it. There is diver available with CCS compiler called 'KBD.c'

c:\program files\picc\examples\ex_lcdkb.c

Click to expand...

Ur circuit diagram is correct and no need to change it.


Good luck.

thanks for the input, but i donot have a CCS compiler.

Suggest you use active low logic. Output low on any of the 4 outputs and then look for low on the 4 inputs. You WILL need pullup resistors on the 4 inputs, internal weak pullups may be ok if the port has them, would go for external myself 1-10k ok, I tend to use 4K7.

Added after 6 minutes:

Simulation gives a good indication that a circuit may work, but this as in many cases it fails to take account of real world conditions. In theory you circuit should work, in practice not.

Added after 5 minutes:

This is 3x4. Maybe it will give you some ideas.

//Read Keypad and returns Digit Value

unsigned char GetKey(void)
{ // Get Keypress Active Low
unsigned char Digit, KeyRead;
C1 = 0; C2 = 1; C3 = 1; // Column 1 On
DelayMs(3);
KeyRead = (P2 & 0x0F);
if (KeyRead == 14) {Digit = 1;goto Skip;} // Read Rows and Translate
if (KeyRead == 13) {Digit = 4;goto Skip;}
if (KeyRead == 11) {Digit = 7;goto Skip;}
if (KeyRead == 7) {Digit = 10;goto Skip;} // Cancel Key

C1 = 1; C2 = 0; C3 = 1; // Column 2 On
DelayMs(3);
KeyRead = (P2 & 0x0F);
if (KeyRead == 14) {Digit = 2;goto Skip;}
if (KeyRead == 13) {Digit = 5;goto Skip;}
if (KeyRead == 11) {Digit = 8;goto Skip;}
if (KeyRead == 7) {Digit = 0;goto Skip;}

C1 = 1; C2 = 1; C3 = 0; // Column 3 On
DelayMs(3);
KeyRead = (P2 & 0x0F);
if (KeyRead == 14) {Digit = 3;goto Skip;}
if (KeyRead == 13) {Digit = 6;goto Skip;}
if (KeyRead == 11) {Digit = 9;goto Skip;}
if (KeyRead == 7) {Digit = 11;} // Call Key

Skip:
Blip();
DelayMs(30);
while ((P2 & 0x0F) != 0x0F);ResetWD(); // Wait for Key Release
return Digit;
}

Hi,
This is a sample code provided in mikroC v8.2:
Hope it helps.
Tahmid.

Hi, whay my PIC18F458 different with your in my proteus? I using Proteus 7.
Now i doing my assingment for this PIC18F458. Can you help me to draw the schematic using PROTEUS with the basic component required to run a PIC18F458. Thanks.

Hi thetravellerzt
the PIC18f458 i shown above in the circuit is the one drawn in OrCad.

can you help me design in proteus please? TQ

Hello thetravellerzt

here is the ckt in Proteus

hi can u help me with 4x3 keypad interfacing in zilog?
thanks!!