<div id="readability-page-1" class="page"><div>
<p>
  복잡하게 디바이스 드라이버까지 작성하지 않고 간단하게 mmap을 사용하여 레지스터에 접근하여 LED를 제어해보려고 합니다. 
</p>







<p>
  핀번호 6번 그라운드와 핀번호 12번 GPIO18에 LED를 연결해주었습니다.
</p>



<figure><img data-lazy-fallback="1" data-attachment-id="6120" data-permalink="https://webnautes.blog/6119/word-image-6119-1/" data-orig-file="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-1.png?fit=500%2C150&amp;ssl=1" data-orig-size="500,150" data-comments-opened="1" data-image-meta="{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;,&quot;orientation&quot;:&quot;0&quot;}" data-image-title="word-image-6119-1" data-image-description="" data-image-caption="" data-medium-file="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-1.png?fit=300%2C90&amp;ssl=1" data-large-file="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-1.png?fit=500%2C150&amp;ssl=1" decoding="async" fetchpriority="high" width="500" height="150" src="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-1.png?resize=500%2C150&amp;ssl=1" alt="" sizes="(max-width: 500px) 100vw, 500px" data-recalc-dims="1" data-old-src="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-1.png?resize=500%2C150&amp;is-pending-load=1#038;ssl=1" data-lazy-srcset="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-1.png?w=500&amp;ssl=1 500w, https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-1.png?resize=300%2C90&amp;ssl=1 300w"></figure>







<figure><img data-lazy-fallback="1" data-attachment-id="6121" data-permalink="https://webnautes.blog/6119/word-image-6119-2/" data-orig-file="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-2.png?fit=1458%2C1538&amp;ssl=1" data-orig-size="1458,1538" data-comments-opened="1" data-image-meta="{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;,&quot;orientation&quot;:&quot;0&quot;}" data-image-title="word-image-6119-2" data-image-description="" data-image-caption="" data-medium-file="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-2.png?fit=284%2C300&amp;ssl=1" data-large-file="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-2.png?fit=971%2C1024&amp;ssl=1" decoding="async" width="1200" height="1266" src="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-2.png?resize=1200%2C1266&amp;ssl=1" alt="" sizes="(max-width: 1200px) 100vw, 1200px" data-recalc-dims="1" data-old-src="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-2.png?resize=1200%2C1266&amp;is-pending-load=1#038;ssl=1" data-lazy-srcset="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-2.png?w=1458&amp;ssl=1 1458w, https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-2.png?resize=284%2C300&amp;ssl=1 284w, https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-2.png?resize=971%2C1024&amp;ssl=1 971w, https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-2.png?resize=768%2C810&amp;ssl=1 768w, https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-2.png?resize=1456%2C1536&amp;ssl=1 1456w, https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-2.png?resize=1200%2C1266&amp;ssl=1 1200w"></figure>







<p>
  BCM2835 데이터 시트에 따르면 LED를 켜고 끄는 데에는 다음 레지스터들을 사용하면 됩니다. 
</p>



<p>
  라즈베리파이3에선 BCM2837이지만 동일하게 동작했습니다. 
</p>



<ul>
<li>
    GPFSELx – GPIO핀을 Input 또는 Ouput으로 사용할지 결정.
  </li>



<li>
    GPSETx – GPIO핀을 하이레벨로 만들어줌. Led가 켜진 상태.
  </li>



<li>
    GPCLRx – GPIO핀을 로우 레벨로 만들어줌. Led가 꺼지는 상태.
  </li>
</ul>







<p>
  GPIO Base Address가 아래처럼 0x 7E20 0000으로 나와 있지만 BCM2835 데이터시트의 1.2.3 ARM physical addresses에 따르면 실제로 접근 시에는 0x 2020 0000부터 시작하는 걸로 생각하면 됩니다. 
</p>



<p>
  하지만 이건 라즈베리파이 1 기준입니다. (<a href="http://www.raspberrypi.org/forums/viewtopic.php?f=6&amp;t=5982" rel="nofollow">http://www.raspberrypi.org/forums/viewtopic.php?f=6&amp;t=5982</a> )
</p>



<figure><img data-lazy-fallback="1" data-attachment-id="6122" data-permalink="https://webnautes.blog/6119/word-image-6119-3/" data-orig-file="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-3.png?fit=581%2C77&amp;ssl=1" data-orig-size="581,77" data-comments-opened="1" data-image-meta="{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;,&quot;orientation&quot;:&quot;0&quot;}" data-image-title="word-image-6119-3" data-image-description="" data-image-caption="" data-medium-file="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-3.png?fit=300%2C40&amp;ssl=1" data-large-file="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-3.png?fit=581%2C77&amp;ssl=1" decoding="async" width="581" height="77" src="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-3.png?resize=581%2C77&amp;ssl=1" alt="" sizes="(max-width: 581px) 100vw, 581px" data-recalc-dims="1" data-old-src="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-3.png?resize=581%2C77&amp;is-pending-load=1#038;ssl=1" data-lazy-srcset="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-3.png?w=581&amp;ssl=1 581w, https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-3.png?resize=300%2C40&amp;ssl=1 300w"></figure>







<p><a href="https://www.raspberrypi.org/forums/viewtopic.php?f=33&amp;t=98740">https://www.raspberrypi.org/forums/viewtopic.php?f=33&amp;t=98740</a>  에 따르면 라즈베리파이2에서는 0x3F20 0000으로 바꾸어서 적용시키면 된다고 합니다. 따라서 GPFSEL0의 시작 주소가 0x7E20 0000이 아니라 0x3F20 0000이 되는 것입니다. 
</p>



<p>
  라즈베리파이3에서도 테스트해보니 동일하게 동작합니다. 
</p>







<p>
  아래에 LED를 제어하는데 사용할 3가지 레지스터의 메모리 주소들을 보여주고 있습니다.
</p>



<figure><img data-lazy-fallback="1" data-attachment-id="6123" data-permalink="https://webnautes.blog/6119/word-image-6119-4/" data-orig-file="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-4.png?fit=574%2C358&amp;ssl=1" data-orig-size="574,358" data-comments-opened="1" data-image-meta="{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;,&quot;orientation&quot;:&quot;0&quot;}" data-image-title="word-image-6119-4" data-image-description="" data-image-caption="" data-medium-file="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-4.png?fit=300%2C187&amp;ssl=1" data-large-file="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-4.png?fit=574%2C358&amp;ssl=1" decoding="async" loading="lazy" width="574" height="358" src="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-4.png?resize=574%2C358&amp;ssl=1" alt="" sizes="(max-width: 574px) 100vw, 574px" data-recalc-dims="1" data-old-src="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-4.png?resize=574%2C358&amp;is-pending-load=1#038;ssl=1" data-lazy-srcset="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-4.png?w=574&amp;ssl=1 574w, https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-4.png?resize=300%2C187&amp;ssl=1 300w"></figure>







<p>
  GPIO18번은 GPF_SEL1레지스터에 해당 항목이 있습니다. 
</p>



<p>
  24번째 비트부터 26번째 비트까지의 값을 001로 바꾸어주면 GPIO18번는 출력모드가 되게 됩니다.
</p>



<figure><table><thead><tr><th><p>
      //gpio[GPFSEL1/4] = 0b00000001000000000000000000000000;    
  <br>
      gpio[GPFSEL1/4] |= (1&lt;&lt;24);    
</p></th></tr></thead></table></figure>



<figure><img data-lazy-fallback="1" data-attachment-id="6124" data-permalink="https://webnautes.blog/6119/word-image-6119-5/" data-orig-file="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-5.png?fit=561%2C436&amp;ssl=1" data-orig-size="561,436" data-comments-opened="1" data-image-meta="{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;,&quot;orientation&quot;:&quot;0&quot;}" data-image-title="word-image-6119-5" data-image-description="" data-image-caption="" data-medium-file="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-5.png?fit=300%2C233&amp;ssl=1" data-large-file="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-5.png?fit=561%2C436&amp;ssl=1" decoding="async" loading="lazy" width="561" height="436" src="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-5.png?resize=561%2C436&amp;ssl=1" alt="" sizes="(max-width: 561px) 100vw, 561px" data-recalc-dims="1" data-old-src="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-5.png?resize=561%2C436&amp;is-pending-load=1#038;ssl=1" data-lazy-srcset="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-5.png?w=561&amp;ssl=1 561w, https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-5.png?resize=300%2C233&amp;ssl=1 300w"></figure>







<p>
  그리고 다음 레지스터들에서 GPIO18번의 위치에 해당되는 비트를 세팅 해주면 LED가 켜지고 꺼지게 할 수 있습니다.
</p>



<figure><img data-lazy-fallback="1" data-attachment-id="6125" data-permalink="https://webnautes.blog/6119/word-image-6119-6/" data-orig-file="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-6.png?fit=553%2C109&amp;ssl=1" data-orig-size="553,109" data-comments-opened="1" data-image-meta="{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;,&quot;orientation&quot;:&quot;0&quot;}" data-image-title="word-image-6119-6" data-image-description="" data-image-caption="" data-medium-file="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-6.png?fit=300%2C59&amp;ssl=1" data-large-file="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-6.png?fit=553%2C109&amp;ssl=1" decoding="async" loading="lazy" width="553" height="109" src="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-6.png?resize=553%2C109&amp;ssl=1" alt="" sizes="(max-width: 553px) 100vw, 553px" data-recalc-dims="1" data-old-src="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-6.png?resize=553%2C109&amp;is-pending-load=1#038;ssl=1" data-lazy-srcset="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-6.png?w=553&amp;ssl=1 553w, https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-6.png?resize=300%2C59&amp;ssl=1 300w"></figure>



<figure><table><thead><tr><th><p>
          //gpio[GPSET0/4] = 0b00000000000001000000000000000000;    
  <br>
          gpio[GPSET0/4] |= (1&lt;&lt;18);   
</p></th></tr></thead></table></figure>



<figure><img data-lazy-fallback="1" data-attachment-id="6126" data-permalink="https://webnautes.blog/6119/word-image-6119-7/" data-orig-file="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-7.png?fit=560%2C99&amp;ssl=1" data-orig-size="560,99" data-comments-opened="1" data-image-meta="{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;,&quot;orientation&quot;:&quot;0&quot;}" data-image-title="word-image-6119-7" data-image-description="" data-image-caption="" data-medium-file="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-7.png?fit=300%2C53&amp;ssl=1" data-large-file="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-7.png?fit=560%2C99&amp;ssl=1" decoding="async" loading="lazy" width="560" height="99" src="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-7.png?resize=560%2C99&amp;ssl=1" alt="" sizes="(max-width: 560px) 100vw, 560px" data-recalc-dims="1" data-old-src="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-7.png?resize=560%2C99&amp;is-pending-load=1#038;ssl=1" data-lazy-srcset="https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-7.png?w=560&amp;ssl=1 560w, https://i0.wp.com/webnautes.blog/wp-content/uploads/2023/09/word-image-6119-7.png?resize=300%2C53&amp;ssl=1 300w"></figure>



<figure><table><thead><tr><th><p>
          //gpio[GPCLR0/4] = 0b00000000000001000000000000000000;   
  <br>
          gpio[GPCLR0/4] |= (1&lt;&lt;18); 
</p></th></tr></thead></table></figure>







<p>
  실행시켜보면 LED가 5번 깜빡이게 됩니다.
</p>



<p>
  pi@raspberrypi:~ $ g++ led.c -o led
</p>



<p>
  pi@raspberrypi:~ $ sudo ./led
</p>







<pre><code>#include &lt;stdlib.h&gt;    
#include &lt;stdio.h&gt;
#include &lt;unistd.h&gt;    
#include &lt;sys/types.h&gt;    
#include &lt;sys/stat.h&gt;    
#include &lt;fcntl.h&gt;    
#include &lt;sys/mman.h&gt;    
        
        
#define GPIO_BASE 0x3F200000    
#define GPFSEL1   0x04  
#define GPSET0    0x1C  
#define GPCLR0    0x28    
        
        
int main()    
{    
    int fd = open( "/dev/mem", O_RDWR|O_SYNC );    
    if ( fd &lt; 0 ){    
        printf( "can't open /dev/mem \n" );    
        exit(-1);    
    }    
        
        
    char *gpio_memory_map = (char *)mmap( 0, 4096, PROT_READ|PROT_WRITE,    
        MAP_SHARED, fd, GPIO_BASE );    
        
    if ( gpio_memory_map == MAP_FAILED )    
    {    
        printf( " Error : mmap \n" );    
        exit(-1);    
    }    
        
            
    volatile unsigned int* gpio = (volatile unsigned int*)gpio_memory_map;    
    //gpio[GPFSEL1/4] = 0b00000001000000000000000000000000;    
    gpio[GPFSEL1/4] |= (1&lt;&lt;24);    
        
    int i;    
    for ( i=0; i&lt;5; i++ )    
    {    
        //gpio[GPSET0/4] = 0b00000000000001000000000000000000;    
        gpio[GPSET0/4] |= (1&lt;&lt;18);   
        sleep(1);    
        
        //gpio[GPCLR0/4] = 0b00000000000001000000000000000000;   
        gpio[GPCLR0/4] |= (1&lt;&lt;18);  
        sleep(1);    
    }    
        
     munmap( gpio_memory_map, 4096);    
    
    return 0;    
}    </code></pre>







<p>
  마지막 업데이트 2019. 2. 18
</p>





</div></div>

멈춤보단 천천히라도

webnautes

복잡하게 디바이스 드라이버까지 작성하지 않고 간단하게 mmap을 사용하여 레지스터에 접근하여 LED를 제어해보려고 합니다. 핀번호 6번 그라운드와 핀번호 12번 GPIO18에 LED를 연결해주었습니다. BCM2835 데이터 시트에 따르면 LED를 켜고 끄는 데에는 다음 레지스터들을 사용하면 됩니다. 라즈베리파이3에선 BCM2837이지만 동일하게 동작했습니다. GPIO Base Address가 아래처럼 0x 7E20 0000으로 나와 있지만 BCM2835 데이터시트의 1.2.3 ARM physical addresses에 따르면 실제로 접근… 더 보기 »C언어로 Raspberry Pi 3의 GPIO 레지스터 접근하여 LED켜보기
The post C언어로 Raspberry Pi 3의 GPIO 레지스터 접근하여 LED켜보기 first appeared on 멈춤보단 천천히라도.

C언어로 Raspberry Pi 3의 GPIO 레지스터 접근하여 LED켜보기

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