Hardware Reference
In-Depth Information
gpio_io.c
The following pages show the program listing for
gpio_io.c
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gpio_io.c : GPIO Access Code
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5 #define BCM2708_PERI_BASE 0x20000000
6 #define GPIO_BASE (BCM2708_PERI_BASE + 0x200000)
7 #define BLOCK_SIZE (4
1024)
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8
9 /
GPIO setup macros. Always use INP_GPIO (x) before using OUT_GPIO(x)
10 or SET_GPIO_ALT(x, y )
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11 #define INP_GPIO(g) \
(ugpio + ((g)/10)) &= ~(7 <<(((g) % 10)
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12 #define OUT_GPIO(g)
(ugpio + ((g)/10)) |= (1 <<(((g) % 10)
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13 #define SET_GPIO_ALT(g,a) \
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(ugpio + (((g)/10))) |= (((a) <=3?(a) + 4 : \
(a)==4?3:2)<<(((g)%10)
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3))
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15
16 #define GPIO_SET
(ugpio+7) /
sets bits
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17 #define GPIO_CLR
(ugpio+10) /
clears bits
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18 #define GPIO_GET
(ugpio+13) /
gets all GPIO input levels
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20 typedef enum {
21 Input = 0, /
GPIO is an Input
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22 Output /
GPIO is an Output
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23 } direction_t;
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25 static volatile unsigned
ugpio;
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Perform initialization to access GPIO registers:
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Sets up pointer ugpio.
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31 static void
32 gpio_init() {
33 int fd;
34 char
map;
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35 /
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36 fd = open("/dev/mem",O_RDWR|O_SYNC);
37 if ( fd < 0 ) {
38 perror("Opening/dev/mem");
39 exit(1);
40 }
41
Needs root access
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