{"id":1179,"date":"2024-06-24T13:53:31","date_gmt":"2024-06-24T13:53:31","guid":{"rendered":"https:\/\/iotthinghub.com\/?p=1179"},"modified":"2024-08-11T15:10:17","modified_gmt":"2024-08-11T15:10:17","slug":"memory-access","status":"publish","type":"post","link":"https:\/\/iotthinghub.com\/?p=1179","title":{"rendered":"Memory access"},"content":{"rendered":"\n

Atmel AVR microcontroller has typically three memories<\/strong><\/p>\n\n\n\n

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\"\"<\/figure>\n<\/div>\n\n\n\n
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  1. RAM (Random Access Memory):-<\/strong> In RAM i.e. static RAM\/CRAM by the GCC compiler place for variables is reserved; also the stack is in the RAM. This memory is volatile, means contents of the variable are lost with switching off a collapse of voltage supply.<\/li>\n\n\n\n
  2. Program memory:- <\/strong>Implementedas Flash memory, again- record ably by page. In it the application program is put down.<\/li>\n\n\n\n
  3. EEPROM:- <\/strong>Not volatile memory i.e. once written contents remain without current supply. Bytes by bytes write\/ read ably. In the EEPROM typically device-specific values are put down like calibration values of sensor.<\/li>\n<\/ol>\n<\/div>\n<\/div>\n\n\n\n
    \"\"<\/figure>\n\n\n\n

    Pointer:<\/strong><\/p>\n\n\n\n

    Whenever we declare a variable, the system allocates somewhere in the memory, an appropriate location to hold the value of the variable. Every byte has a unique address number. The location will have its own address number<\/p>\n\n\n\n

                Example:- uint8_t myByte=8;<\/strong><\/p>\n\n\n\n

    Let\u2019s us assume that the system has chosen the address location 0x00f for myByte. Then the concept is<\/p>\n\n\n\n

    \"\"<\/figure>\n\n\n\n

    A pointer variable is nothing but a variable that contains an address, which is a location of another variable in memory.<\/p>\n\n\n\n

    Declaration of pointer variable<\/p>\n\n\n\n

                data_type *pointer_name;<\/strong><\/p>\n\n\n\n

                i.e. uint8_t *p; \/** unsigned 8 bit integer **\/<\/strong><\/p>\n\n\n\n

    This tells the compiler three things about the variable pointer_name-<\/p>\n\n\n\n

      \n
    1. The asterisk(*) tells that the variable pointer_name is a pointer variable<\/li>\n\n\n\n
    2. pointer_name needs a memory location<\/li>\n\n\n\n
    3. pointer_name points to a variable of data type<\/li>\n<\/ol>\n\n\n\n

      Declaration style<\/p>\n\n\n\n

      style1 —-> int* p;<\/p>\n\n\n\n

      style2 —-> int *p;<\/p>\n\n\n\n

      style1 —-> int * p;<\/p>\n\n\n\n

      \"\"<\/figure>\n\n\n\n

      Pointers and arrays<\/strong><\/p>\n\n\n\n

                  C:\/> int Data[4]={1,2,3,4,5};<\/strong><\/p>\n\n\n\n

      Let the address begin with 0x0000H, than<\/p>\n\n\n\n

      If we declare p as an integer pointer, than we can make the pointer p to point to the array data by<\/p>\n\n\n\n

                  p=x;  \/\/ equivalent to p=&x[0]<\/strong><\/p>\n\n\n\n

       Now we can access every value of Data variable using p++ to move from one element to another.<\/p>\n\n\n\n

      \"\"<\/figure>\n\n\n\n

      There is necessary special function in order to read\/write data from this memory. The Header file to access this memory is<\/p>\n\n\n

      \n#include<avr\/pgmspace.h>\n<\/pre><\/div>\n\n\n
      Write data to flash memory<\/p>\n\n\n
      \nconst data_type variable_name [] PROGMEM\n<\/pre><\/div>\n\n\n
      Read data from flash memory<\/p>\n\n\n
      \nvariable=pgm_read_X(& variable_name[++]);\n<\/pre><\/div>\n\n\n
      where X represents the variable data type<\/p>\n\n\n\n
      \"\"<\/figure>\n\n\n\n
      \"\"<\/figure>\n\n\n\n
      Let\u2019s build a wave to run a buzzer. Just connect the buzzer + terminal to PB0 pin of ATtiny13A and \u2013 terminal to ground. Here we store the value in Flash memory and read the data. It\u2019s a simple program as follow-<\/p>\n\n\n
      \n\/************************************************************************************************\n*************************************************************************************************\nThis program will genarate a sound wave\n*************************************************************************************************\n\t\tSubeer Kumar Sarkar\n\t\tElectrical & Electronic Engineer\n************************************************************************************************\n************************************************************************************************\n***********************************************************************************************\/\n#include<avr\/io.h>\n#include<util\/delay.h>\n#include<avr\/pgmspace.h>\nconst uint8_t sound[512] PROGMEM ={\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,\n0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff\n};\nint main(void)\n{\nuint8_t generarion;\nDDRB|=(1<<DDB0);\nwhile(1)\n\t{\nfor(int i=0;i<512;i++)\n\t\t{\n\t\t\tgenerarion=(uint8_t*)pgm_read_word(&sound[i]);\n\t\t\tgenerarion ? (PORTB|=(1<<PB0)) : (PORTB&=~(1<<PB0));\n\t\t\t_delay_ms(1);\n\t\t}\t\n\t}\nreturn 0;\n}\n<\/pre><\/div>\n\n\n
      \n
      \n
      \n
      download<\/a><\/div>\n<\/div>\n<\/div>\n\n\n\n
      \n
      Download the full program with proteus simulation<\/a><\/strong><\/p>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"
      Atmel AVR microcontroller has typically three memories Pointer: Whenever we declare a variable, the system allocates somewhere in the memory, an appropriate location to hold the value of the variable. Every byte has a unique address number. The location will have its own address number             Example:- uint8_t myByte=8; Let\u2019s us assume that the system […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[10],"tags":[],"class_list":["post-1179","post","type-post","status-publish","format-standard","hentry","category-flash-memory"],"_links":{"self":[{"href":"https:\/\/iotthinghub.com\/index.php?rest_route=\/wp\/v2\/posts\/1179","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/iotthinghub.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/iotthinghub.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1179"}],"version-history":[{"count":20,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=\/wp\/v2\/posts\/1179\/revisions"}],"predecessor-version":[{"id":2556,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=\/wp\/v2\/posts\/1179\/revisions\/2556"}],"wp:attachment":[{"href":"https:\/\/iotthinghub.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1179"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1179"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1179"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}