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comparison py/touch/touch.c @ 454:dce9f7841696

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rough touch sensor
author Matt Johnston <matt@ucc.asn.au>
date Fri, 21 Dec 2012 23:30:16 +0800
parents
children bed65c321b46
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453:0af7b38a1847 454:dce9f7841696
1 //
2 // How to access GPIO registers from C-code on the Raspberry-Pi
3 // Example program
4 // 15-January-2012
5 // Dom and Gert
6 //
7
8
9 // Access from ARM Running Linux
10
11 #define BCM2708_PERI_BASE 0x20000000
12 #define GPIO_BASE (BCM2708_PERI_BASE + 0x200000) /* GPIO controller */
13
14
15 #include <stdio.h>
16 #include <string.h>
17 #include <stdlib.h>
18 #include <dirent.h>
19 #include <fcntl.h>
20 #include <assert.h>
21 #include <sys/mman.h>
22 #include <sys/types.h>
23 #include <sys/stat.h>
24
25 #include <unistd.h>
26
27 #define PAGE_SIZE (4*1024)
28 #define BLOCK_SIZE (4*1024)
29
30 int mem_fd;
31 char *gpio_mem, *gpio_map;
32 char *spi0_mem, *spi0_map;
33
34
35 // I/O access
36 volatile unsigned *gpio;
37
38
39 // GPIO setup macros. Always use INP_GPIO(x) before using OUT_GPIO(x) or SET_GPIO_ALT(x,y)
40 #define INP_GPIO(g) *(gpio+((g)/10)) &= ~(7<<(((g)%10)*3))
41 #define OUT_GPIO(g) *(gpio+((g)/10)) |= (1<<(((g)%10)*3))
42 #define SET_GPIO_ALT(g,a) *(gpio+(((g)/10))) |= (((a)<=3?(a)+4:(a)==4?3:2)<<(((g)%10)*3))
43
44 #define FSEL_OFFSET 0 // 0x0000
45 #define SET_OFFSET 7 // 0x001c / 4
46 #define CLR_OFFSET 10 // 0x0028 / 4
47 #define PINLEVEL_OFFSET 13 // 0x0034 / 4
48 #define EVENT_DETECT_OFFSET 16 // 0x0040 / 4
49 #define RISING_ED_OFFSET 19 // 0x004c / 4
50 #define FALLING_ED_OFFSET 22 // 0x0058 / 4
51 #define HIGH_DETECT_OFFSET 25 // 0x0064 / 4
52 #define LOW_DETECT_OFFSET 28 // 0x0070 / 4
53 #define PULLUPDN_OFFSET 37 // 0x0094 / 4
54 #define PULLUPDNCLK_OFFSET 38 // 0x0098 / 4
55
56
57 #define GPIO_GET(g) ((*(gpio+PINLEVEL_OFFSET) & (1<<(g))) >> (g))
58 #define GPIO_SET(g) (*(gpio+SET_OFFSET) = 1<<(g)) // sets bits which are 1 ignores bits which are 0
59 #define GPIO_CLR(g) (*(gpio+CLR_OFFSET) = 1<<(g))// clears bits which are 1 ignores bits which are 0
60
61 #define TOUCH_IN 24
62 #define TOUCH_OUT 25
63
64 void setup_io();
65
66 int main(int argc, char **argv)
67 {
68 int g,rep;
69
70 // Set up gpi pointer for direct register access
71 setup_io();
72
73 // Switch GPIO 7..11 to output mode
74
75 /************************************************************************\
76 * You are about to change the GPIO settings of your computer. *
77 * Mess this up and it will stop working! *
78 * It might be a good idea to 'sync' before running this program *
79 * so at least you still have your code changes written to the SD-card! *
80 \************************************************************************/
81
82
83 INP_GPIO(TOUCH_IN);
84 INP_GPIO(TOUCH_OUT);
85 OUT_GPIO(TOUCH_OUT);
86
87 int num = 1000;
88 int sum = 0;
89
90 while (1)
91 {
92 int n;
93 sum = 0;
94 for (n = 0; n < num; n++)
95 {
96 GPIO_CLR(TOUCH_OUT);
97 usleep(1000);
98 GPIO_SET(TOUCH_OUT);
99 while (GPIO_GET(TOUCH_IN) == 0)
100 {
101 sum++;
102 }
103 }
104 printf("total %f\n", (float)sum / num);
105 }
106 return 0;
107
108 } // main
109
110
111 //
112 // Set up a memory regions to access GPIO
113 //
114 void setup_io()
115 {
116 /* open /dev/mem */
117 if ((mem_fd = open("/dev/mem", O_RDWR|O_SYNC) ) < 0) {
118 printf("can't open /dev/mem \n");
119 exit (-1);
120 }
121
122 /* mmap GPIO */
123
124 // Allocate MAP block
125 if ((gpio_mem = malloc(BLOCK_SIZE + (PAGE_SIZE-1))) == NULL) {
126 printf("allocation error \n");
127 exit (-1);
128 }
129
130 // Make sure pointer is on 4K boundary
131 if ((unsigned long)gpio_mem % PAGE_SIZE)
132 gpio_mem += PAGE_SIZE - ((unsigned long)gpio_mem % PAGE_SIZE);
133
134 // Now map it
135 gpio_map = (unsigned char *)mmap(
136 (caddr_t)gpio_mem,
137 BLOCK_SIZE,
138 PROT_READ|PROT_WRITE,
139 MAP_SHARED|MAP_FIXED,
140 mem_fd,
141 GPIO_BASE
142 );
143
144 if ((long)gpio_map < 0) {
145 printf("mmap error %d\n", (int)gpio_map);
146 exit (-1);
147 }
148
149 // Always use volatile pointer!
150 gpio = (volatile unsigned *)gpio_map;
151
152
153 } // setup_io