7 led segments source code in Keil C

[coca99]

Hi Guys,
This is the first time I have just started with Keil C .
Yet, I have no idea about this concept.
Please clarify it for me.
Thank you all.

#include <stdio.h>
#include "NUC1xx.h"
#include "Driver\DrvGPIO.h"
#include "Driver\DrvSYS.h"
#include "Seven_Segment.h"
#define SEG_N0   0x82 
#define SEG_N1   0xEE 
#define SEG_N2   0x07 
#define SEG_N3   0x46 
#define SEG_N4   0x6A  
#define SEG_N5   0x52 
#define SEG_N6   0x12 
#define SEG_N7   0xE6 
#define SEG_N8   0x02 
#define SEG_N9   0x62
#define SEG_N10  0x22
#define SEG_N11  0x1A
#define SEG_N12  0x93
#define SEG_N13  0x0E
#define SEG_N14  0x13
#define SEG_N15  0x33

unsigned char SEG_BUF[16]={SEG_N0, SEG_N1, SEG_N2, SEG_N3, SEG_N4, SEG_N5, SEG_N6, SEG_N7, SEG_N8, SEG_N9, SEG_N10, SEG_N11, SEG_N12, SEG_N13, SEG_N14, SEG_N15}; // this is an array of Heximal character from 0 to F.

void show_seven_segment(unsigned char no, unsigned char number)
{
    unsigned char temp,i;
    temp=SEG_BUF[number];

    for(i=0;i<8;i++)
        {
        if((temp&0x01)==0x01)//???????????????             
           DrvGPIO_SetBit(E_GPE,i);
           else
           DrvGPIO_ClrBit(E_GPE,i);       
           temp=temp>>1;
        }
        DrvGPIO_SetBit(E_GPC,4+no); 

}

***: could any one tell me how the loop works and why the condition is to do with 0x01

Thank you

[ddanbe]

Hi coca99, welcome at Daniweb!
The loop tests the bits in temp by ANDing with 0x01 on line 32.
If this gives 0x01 than bit i of DrvGPIO is set, else it is cleared. The next bit of temp will be tested after a right shift by 1 on line 38.

[coca99]

Thank ddanbe.
Yet, when I read the defined term in Hex, there are no value which related to 0x01 when we mention (==0x01). In addition, only the four-following define include (temp&0x01)==0x01.

define SEG_N2 0x07 (//7//0111)

define SEG_N12 0x93 (//147//10010011)

define SEG_N14 0x13 (//19//10011)

define SEG_N15 0x33 (//51//110011)

In my document, the led will set if we use ClearBit and vice versa. Thus, ostensibly I think (==0x01) is the range/condition out of the SEG_BUF.
However, with the four define above, the first binary value =1 so I still do not understand the term (temp&0x01)==0x01.

Please could you explain more detailed for me.

Thank you so much

[ddanbe]

Using 4 bits here to keep it simple
Say temp is equal to 0110 (=6 decimal)
0x01 I will represent by 0001

Anding will give:
  0110
& 0001
  ----
  0000 ---> not equal to 0001 so  DrvGPIO_ClrBit(E_GPE,i); is executed

Next we do a right shift of one and temp becomes 0011, after anding:
  0011
& 0001
  ----
  0001 ---> equal to 0001 so  DrvGPIO_SetBit(E_GPE,i); is executed 

And so on till the loop is finished.
Hope this makes it a bit(no pun intended) clearer.

[coca99]

thank..I got it today :)