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POHandle GPIO in User Space ARM9 Embedded Linux AM1808
 

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  1. POHandle GPIO in User Space ARM9 Embedded Linux AM1808
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    <p>I have to interface my GSM module with the AM1808 based on ARM9.</p> <p>I have assigned all the GPIO pins to the Da850.c as well as mux.h files. I successfully created a uImage and inserted that image in my flash.</p> <p>I need to handle some of that GPIO from User application.</p> <p>I know that we can handle the GPIO from the Kerel space but i need to handle from the user space.</p> <p>As for example I have assigned a GPIO for power key to GSM module. I need to change the pin means (HIGH or LOW) through application.</p> <p>Ok i have written a following code to access it from the User Space,</p> <pre><code>#include &lt;stdio.h&gt; #include &lt;time.h&gt; #include &lt;signal.h&gt; #include &lt;fcntl.h&gt; #include &lt;sys/mman.h&gt; #include &lt;stdlib.h&gt; #include &lt;unistd.h&gt; #include "GSMpwr.h" #define BS_GSM_PWR_REGISTER 0x01E26014 #define BS_DCDS_MASK 0x00000004 int fd; // Memory device descriptor unsigned long *pPWR; unsigned short GetGSMpwr(void) { #if defined __HOST_ARM unsigned long dcd_value = *pPWR; return (pwr_value &gt;&gt; 7) &amp; 0x01; #endif } void InitializeGSMpwr(void) { #if defined __HOST_ARM int page_size = getpagesize(); unsigned int MAP_addr; unsigned int reg_addr; unsigned char *pTemp; // Pointer to GSMpwr register /* * Open memory and get pointer to GSMpwr register in the FPGA */ if((fd = open("/dev/mem", O_RDWR | O_SYNC)) &lt; 0) { printf("failed to open /dev/mem"); return; } else { MAP_addr = (BS_GSM_PWR_REGISTER &amp; ~(page_size - 1)); pTemp = (unsigned char *)mmap(NULL, page_size,(PROT_READ | PROT_WRITE),MAP_SHARED,fd,MAP_addr); if((pTemp == MAP_FAILED) || (pTemp == NULL)) { printf("failed to map /dev/mem"); return; } else { printf(“Memory Mapped at Address %p. \n”,pTemp); } virt_addr = map_base + (control &amp; MAP_MASK); reg_addr = (BS_GSM_PWR_REGISTER &amp; (page_size - 1)); pPWR = (unsigned long*)(pTemp + reg_addr); printf("GSM PWR PIN mapped in Application\n"); } </code></pre> <p>I can only read that pin through this code, Now i want to use that pin as an output and want to go high and low with the time interval of 3sec.</p>
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    1. USParthiv Shah
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    1. CODuplicate: http://stackoverflow.com/questions/15634450/handle-gpios-in-user-space-for-embedded-linux-arm9
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    2. COMy answer was clear enough, and yet, you have chosen a different approach, incorrect one. This will not work from user space, because your process has it's own addressing space.
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      1. USAndrejs Cainikovs
 

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