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