Discovery with LCD and 4x3 keypad example

[spiovan9]

Posted on December 12, 2010 at 15:38

The original post was too long to process during our migration. Please click on the attachment to read the original post.

[spiovan9]

Posted on January 02, 2011 at 20:15

Hi all,

Here's an improved code for the 4x3 keypad with debounce and autorepeat.

With STM8S 2MHz clock it performs pretty close to the PC keyboard.

The action() function is out from the keypad management state machine for clarity.

Suggestions and improvements are welcome.

Hope it helps.

Merry Xmas and happy holidays

Steven

u8 key = 255;

u8 oldkey = 255;

u8 AutoRptMax = 64;

u8 AutoRptCount = 0;

while(1)

    {

        key = GetKeyPressed(); //Scan the keypad to getting the code of the key pressed

    

        // < Is it a valid key pressed ? >

        if (key < 12) // YES

        {

            // < Is key still the old one ? >

            if (key == oldkey) // YES

            {

                // (Start counting for autorepeat to occour)

                DelayMS(50);

                AutoRptCount++;

                

                // < Is time to execute the key action? >

                if (AutoRptCount >= AutoRptMax) // YES

                {

                    Action(key); // perform the action according to the key code

                    AutoRptCount = 0; // reset the autorepeat counter to get ready for the next autorepeat event

                    AutoRptMax = 16; // make the autorepeat limit short for speeding up the next repetition when keeps keypressing

                }

            }

            else // NO, the key is new brand

            {

                Action(key); // perform the action according to the key code

                DelayMS(50); // and also make a little debouncing

            }

            

        } // END if (key < 12)

        

        else // NO, the key is not among the 12 defined keys

        {

            // < Was the key pad released ? >

            if (oldkey < 255 ) // YES

            {

                AutoRptCount = 0; // reset the autorepeat counter

                AutoRptMax = 128; // and restart using the first typing delay long

            }            

        }

        

        oldkey = key;

    }

void Action(u8 key)

{

    switch(key)

    {

        case 9: // backspace (mode entry is ''right after writing'' so we need to cursor left twice)

            LCD_DATA(0x10,0);

            LCD_CHR(32);

            LCD_DATA(0x10,0);

        break;

        case 11:

            LCD_DATA(0x14,0); // cursor right

        break;

       

        default:

            LCD_CHR(key + 48 + 1); // display keycode

        break;

    }

}

void DelayMS(int delay)

{

    int nCount = 0;

    while (delay != 0)

    {

        nCount = 100;

        while (nCount != 0)

        {

            nCount--;

        }

        delay--;

    }

}

[nad]

Posted on December 23, 2010 at 01:26

thank you for your code.

Can you give me the reference of the keyboard(4*3) that you used??

best regards

[Andrew Neil]

Posted on December 23, 2010 at 08:33

Look at the JPEG attachment to the original post:

You can see that it's a hand-made keypad!

The connections for the rows & columns, and the key layout are described in the original post.

[spiovan9]

Posted on December 23, 2010 at 13:52

Hi George,

the 4x3 keypad is home made. I've bought 12 single push-buttons and wired them together on a prototyping pcb as you can see in the photo.

Stefano