File content as of revision 3:7d6b9684595c:

#include "MCP23008_Keypad.h"
#include "mbed.h"
 


// Keypad layout:
//                [row][col]   Col0 Col1 Col2 Col3 
char const kpdLayout[4][4] = {{'1' ,'2' ,'3' ,'A'},  //row0
                              {'4' ,'5' ,'6' ,'B'},  //row1
                              {'7' ,'8' ,'9' ,'C'},  //row2
                              {'*' ,'0' ,'#' ,'D'}}; //row3

//NIBBLE LOW=0000,  HIGH= 0111 1011 1101 1110    Col  (x)
const char KpdInMask[4] ={0xe0,0xd0,0xb0,0x70};

//NIBBLE HIGH=1111,  LOW= 0111 1011 1101 1110    Rows (y)
const char KpdOutMask[4]={0xfe,0xfd,0xfb,0xf7};  
    


MCP23008_Keypad::MCP23008_Keypad(PinName SDApin, PinName SCLpin, int MCP23008Address) : i2c(SDApin, SCLpin) {
    char cmd[2];
    
    _addr = MCP23008Address;
    i2c.frequency(100000);      //set I2C frequency to 100Khz
    cmd[0] = 0x00;              //IODIR register
    cmd[1] = 0xf0;              //Bit7 - 4 are inputs and rest outputs
    i2c.write(_addr, cmd, 2);   //write IODIR setting to MCP23008
}

char MCP23008_Keypad::ReadKey() {
    char KeyValue, Done=0;
    uint16_t y, x;
    char cmd[2];
    
    //delay_ms(ContactBounceTime);  //warning no contact bounce protection
                                    //call read_key more than once with delay
                                    //between if key stay constant then key is pressed
    y = 0;
    while((y < 4) && (!Done))
    {
        cmd[0] = 0x09;
        cmd[1] = KpdOutMask[y];
        i2c.write(_addr, cmd, 2);           //write mask value to MCP23008 GPIO register
      
        wait(0.01);  

        cmd[0] = 0x09;
        i2c.write(_addr, cmd, 1);
        i2c.read(_addr, cmd, 1);
        KeyValue = cmd[0] & 0xf0;           //read 4 MSB bits from MCP23008 GPIO register
        
        if(KeyValue == KpdInMask[0])
            x = 0;
        else if(KeyValue == KpdInMask[1])
            x = 1;
        else if(KeyValue == KpdInMask[2])
            x = 2;
        else if(KeyValue == KpdInMask[3])
            x = 3;
        else
        {
            KeyValue='\0';                  //more than one key was pressed or no key in this row.
            x=9;          
        }
        if(x != 9)
        {
            Done = 1;                       //valid key found
            KeyValue = kpdLayout[x][y];     //convert to a character eg. '1','2','3','#','*'
        }
        y++;
    }
    return(KeyValue);
}