Chapter 18 74HC595 & 7-segment display.
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int
main
(
void
)
{
int
i
;
i f
(
wiringPiSetup
()
= =
-
1
) {
//when initialize wiring failed,print messageto screen
printf
(
"setup wiringPi failed !"
) ;
r e turn
1
;
}
pinMode
(
dataPin
,
OUTPUT
);
pinMode
(
latchPin
,
OUTPUT
);
pinMode
(
clockPin
,
OUTPUT
);
w h ile
(
1
){
f o r
(
i
=
0
;
i
<
sizeof
(
num
);
i
++){
digitalWrite
(
latchPin
,
LOW
);
_shiftOut
(
dataPin
,
clockPin
,
MSBFIRST
,
num
[
i
]);
//Output the figures and the
highest level is transfered preferentially.
digitalWrite
(
latchPin
,
HIGH
);
delay
(
500
);
}
f o r
(
i
=
0
;
i
<
sizeof
(
num
);
i
++){
digitalWrite
(
latchPin
,
LOW
);
_shiftOut
(
dataPin
,
clockPin
,
MSBFIRST
,
num
[
i
]
&
0x7f
) ;
//Use the "&0x7f" to
display the decimal point.
digitalWrite
(
latchPin
,
HIGH
);
delay
(
500
);
}
}
r e turn
0
;
}
First, put encoding of “0”-“F” into the array.
unsigned
char
num
[]={
0xc0
,
0xf9
,
0xa4
,
0xb0
,
0x99
,
0x92
,
0x82
,
0xf8
,
0x80
,
0x90
,
0x88
,
0x83
,
0xc6
,
0xa1
,
0x86
,
0x8e
};
In the “for” cycle of loop() function, use 74HC595 to output contents of array “num” successively.
SevenSegmentDisplay can correctly display the corresponding characters. Pay attention to that in shiftOut
function, the transmission bit, flag bit highest bit will be transmitted preferentially.
for
(
i
=
0
;
i
<
sizeof
(
num
);
i
++){
digitalWrite
(
latchPin
,
LOW
);
_shiftOut
(
dataPin
,
clockPin
,
MSBFIRST
,
num
[
i
]);//Output the figures and the
highest level is transfered preferentially.
digitalWrite
(
latchPin
,
HIGH
);
delay
(
500
);
}
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