Getopt

#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int
main (int argc, char **argv)
{
  int aflag = 0;
  int bflag = 0;
  char *cvalue = NULL;
  int index;
  int c;

  opterr = 0;

  while ((c = getopt (argc, argv, "abc:")) != -1)
    switch (c)
      {
      case 'a':
        aflag = 1;
        break;
      case 'b':
        bflag = 1;
        break;
      case 'c':
        cvalue = optarg;
        break;
      case '?':
        if (optopt == 'c')
          fprintf (stderr, "Option -%c requires an argument.\n", optopt);
        else if (isprint (optopt))
          fprintf (stderr, "Unknown option `-%c'.\n", optopt);
        else
          fprintf (stderr,
                   "Unknown option character `\\x%x'.\n",
                   optopt);
        return 1;
      default:
        abort ();
      }

  printf ("aflag = %d, bflag = %d, cvalue = %s\n",
          aflag, bflag, cvalue);

  for (index = optind; index < argc; index++)
    printf ("Non-option argument %s\n", argv[index]);
  return 0;
}

Here are some examples showing what this program prints with different combinations of arguments:

% testopt
aflag = 0, bflag = 0, cvalue = (null)

% testopt -a -b
aflag = 1, bflag = 1, cvalue = (null)

% testopt -ab
aflag = 1, bflag = 1, cvalue = (null)

% testopt -c foo
aflag = 0, bflag = 0, cvalue = foo

% testopt -cfoo
aflag = 0, bflag = 0, cvalue = foo

% testopt arg1
aflag = 0, bflag = 0, cvalue = (null)
Non-option argument arg1

% testopt -a arg1
aflag = 1, bflag = 0, cvalue = (null)
Non-option argument arg1

% testopt -c foo arg1
aflag = 0, bflag = 0, cvalue = foo
Non-option argument arg1

% testopt -a -- -b
aflag = 1, bflag = 0, cvalue = (null)
Non-option argument -b

% testopt -a -
aflag = 1, bflag = 0, cvalue = (null)
Non-option argument -

An option character in this string can be followed by a colon (‘:’) to indicate that it takes a required argument. If an option character is followed by two colons (‘::’), its argument is optional.

This optarg is set by getopt to point at the value of the option argument, for those options that accept arguments.

 

Reference

[1] http://www.gnu.org/software/libc/manual/html_node/Using-Getopt.html

[2] http://www.gnu.org/software/libc/manual/html_node/Example-of-Getopt.html

[3] http://en.wikipedia.org/wiki/Getopt

MAKEFILE built-in function

How to implement built-in function as below

Text-processing function

https://www.gnu.org/software/make/manual/html_node/Text-Functions.html#Text-Functions

$(patsubst %.c,%.o,x.c.c bar.c)

Result: ‘x.c.o bar.o’

$(sort foo bar lose)

Result:‘bar foo lose’

$(word 2, foo bar baz)

Result:‘bar’

Filename manipulate function

https://www.gnu.org/software/make/manual/html_node/File-Name-Functions.html

$(dir src/foo.c hacks)

Result:‘src/ ./’

$(notdir src/foo.c hacks)

Result:‘foo.c hacks’

$(suffix src/foo.c src-1.0/bar.c hacks)

Result:‘.c .c’

$(addprefix src/,foo bar)

Result:‘src/foo src/bar’

linux command – grep

 

 

dmesg | grep -i usb

[option]

“-i” ignore the case.

cat /var/log/dmesg | less

 

 

Reference

http://manpages.ubuntu.com/manpages/utopic/man1/dmesg.1.html

scatter

 

Reference

http://www.keil.com/support/man/docs/uv4/uv4_dg_l51loc.htm

Keil BL51 Locate

 

http://www.keil.com/support/man/docs/armlink/armlink_pge1362075691804.htm

http://www.keil.com/forum/14954/scatter-file/

http://www.keil.com/support/man/docs/armlink/armlink_pge1362075656353.htm

http://www.keil.com/support/docs/3237.htm

http://www.keil.com/support/man/docs/ARMCC/ARMCC_chr1359124982450.htm

Understanding lvalues and rvalues in C and C++

lvalues stands for left-values and rvalues is right-values[2]

lvalue is an expression referring to an object

Data storage for rvalues describes in ASM.[1]

mov #1, n

we could see 1 is a contant number, not a variable. the rvalue 1 never appears as an object in the data space.

 

Reference

[1] http://ieng9.ucsd.edu/~cs30x/Lvalues%20and%20Rvalues.htm

[2] http://www.c4learn.com/c-programming/c-r-value-expression/

[3] http://eli.thegreenplace.net/2011/12/15/understanding-lvalues-and-rvalues-in-c-and-c experitment

Array initialization

Basic initialization

int myArray[10] = { 5, 5, 5, 5, 5, 5, 5, 5, 5, 5 };

other syntax 

int myArray[10] = { [4] = 5, [2] = 5 }; 

is equivalent to

int myArray[6] = { 0, 0, 5, 0, 5, 0 };

initialize a range of elements to the same value

int myArray[10] = {[0 ... 9] = 5};

Elements with missing values will be initialized to 0:

int myArray[10] = { 1, 2 }; // initialize to 1,2,0,0,0...

So this will initialize all elements to 0:

int myArray[10] = { 0 }; // all elements 0(only for Zero initial)

Remember that objects with static storage duration will initialize to 0 if no initializer is specified:

static int myArray[10]; // all elements 0

In C++, an empty initialization list will also initialize every element to 0. This is not allowed with C:

int myArray[10] = {}; // all elements 0 in C++

And that "0" doesn't necessarily mean "all-bits-zero", so using the above is better and more portable than memset(). (Floating point values will be initialized to +0, pointers to null value, etc.)
Reference
[1] http://stackoverflow.com/questions/201101/how-to-initialize-an-array-in-c
[2] https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html
[3] http://www.lemoda.net/c/array-initialization/ (experiment)

Inline Functions versus Macros

add my commend into the content

1. Inline functions follow all the protocols of type safety enforced on normal functions.
• more safe then the macro, especially, for the type defination.
• for the type check, macro is checked by prepocessor, and inline functions is checked by compilar.
2. Inline functions are specified using the same syntax as any other function except that they include the inline keyword in the function declaration.
• only difference is keyword “inline”
3. Expressions passed as arguments to inline functions are evaluated once. In some cases, expressions passed as arguments to macros can be evaluated more than once.
• more variable for arguments
4. There is no risk if called multiple times. But there is risk in macros which can be dangerous when the argument is an expression.
5. functions can include multiple lines of code without trailing backlashes.
6. functions have thier own scope for variables and they can return a value.
7. debuging

Reference

[1] http://msdn.microsoft.com/en-us/library/bf6bf4cf.aspx

[2] http://www.thegeekstuff.com/2013/04/c-macros-inline-functions/

function and function-like macro

if we use the same name for those things. avoid the prepocessor will expand the function first, we usaully add parenthese to prevent.

simple example

#include <stdio.h>
#define test(x) __test(x)
#define __test(x) printf("\n%d\n", x + 1);

int test(int x);
#undef test

int main()
{
    test(1);
}
int (test)(int x)
{
    printf("\n%d\n", x);
}

Referemce

http://stackoverflow.com/questions/13600790/what-do-the-parentheses-around-a-function-name-mean

samba

 

smbpasswd

-a add new accout

-U change password

Reference

[1] https://www.samba.org/samba/docs/man/manpages/smbpasswd.8.html

CRP

CRP(Code read protection) is a way to avoid someone to get code from flash.

CRP

In C, Keyword “static”

#include <stdio.h>
 
int global_var;        //statically allocated as a global variable
static int static_var; //statically allocated but only accessible within file
 
void my_function(void){
     static int my_static = 0; //statically allocated, accessible within my_function
     int my_stack = 0; //allocated on the stack
 
     printf("my_static:%d, my_stack:%d\n", my_static, my_stack);
     my_stack++;
     my_static++;
}

Answer: 

my_static:0, my_stack:0
my_static:1, my_stack:0
my_static:2, my_stack:0
my_static:3, my_stack:0
my_static:4, my_stack:0

Reference

[1] http://coactionos.com/embedded%20design%20tips/2013/10/18/Tips-RAM-Flash-Usage-in-Embedded-C-Programs/

RAM/Flash Usage in Embedded C Programs

 

Read-only memory(Flash)

Data Section

int data_variable = 500;

Read-only date

constant

const int read_only_variable = 2000;

Text(code)

“literal pool” may in the function.

void my_function(void){
     int x;
     x = 200;
     printf("X is %d\n", x);
}

Read-Write Data(RAM)

Data section

int data_var = 500; //require flash memory to stored.

BSS section

int bss_var0;
int bss_var1 = 0;

//doesn’t need require flash memory to stored.

Heap section

static int static_var;

buffer = malloc(512);

Stack section

int my_function(int a, int b, int c, int d)

Reference

[1] http://coactionos.com/embedded%20design%20tips/2013/10/18/Tips-RAM-Flash-Usage-in-Embedded-C-Programs/

Assembly command note

 

The syntax of MOV can also be more complex as the following examples show.^[7]

MOV EAX, [EBX]	  ; Move the 4 bytes in memory at the address contained in EBX into EAX
MOV [ESI+EAX], CL ; Move the contents of CL into the byte at address ESI+EAX

 

Reference

[1] http://en.wikipedia.org/wiki/Assembly_language

Time Stamp

for keil compilar environment, they had a defination for time stamp, therefore we could use that to be a release note for product purpose.

how to use?

printf("%s %s",__DATE__,__TIME__);

or you could assign memory for them.

U8 KC_DATA Datestring[sizeof(__DATE__)];
U8 KC_DATA Timestring[sizeof(__TIME__)];


memcpy(Datestring, &__DATE__, sizeof(__DATE__));
memcpy(Timestring, &__TIME__, sizeof(__TIME__));

 

Reference

[1] http://www.keil.com/forum/2789/display-time-and-date/

compilar a specific memory address for variable and function

Compiler-specific Features [4]

function attributs

assign a section for place function code [1,2]

Variable attributs

locating a variable at absolute memory address [3]

Reference

[1] http://www.keil.com/support/man/docs/armccref/armccref_Cacbgief.htm

[2] http://www.keil.com/forum/13875/-at-for-function-address/

[3] http://www.keil.com/support/docs/2829.htm

[4] http://www.keil.com/support/man/docs/armccref/armccref_chdfijae.htm

Xmodem

Note,

there has three ways to sent file to destination with “Tera term”.

1. Checksum

128-byte packets

2. CRC

128-byte packets

3. 1k

1024-byte packets was the most popular such solution. In this case, the throughput at 9600 bit/s is 81%

lsz [2]

-vv verbose

-X xmodem

-k 1k

-b binary

 

Reference

[1] http://en.wikipedia.org/wiki/XMODEM

[2] https://opengear.zendesk.com/entries/22923362-Serial-port-file-transfer-using-X-Y-Zmodem

Declarations

C 99 provide programmer a way to save a memory space.

struct DM {

int x,

char* z[]

}

z just a label, compilar won’t allocate a memory for that, and this declaration only could put in last of structure declaration. therefore if we need to allocate a space for this structure when we need to store a data in variable z, otherwise we will assign wrong address which is next to variable x.

 

Reference

[1] C in a nutshell

Keil Firmware Binary

 

Normally, Keil will build the HEX file for Magic Flash to burn the code to MCU or .axf for mvisual.

but it’s not for binary code. therefore we need to using some ways to convert HEX to binary.

1.

C:\Keil\ARM\ARMCC\bin\fromelf.exe --bin --output=myprog.bin myprog.axf[1,2]

2.

C:\Keil\ARM\bin\ElfDwt.exe <filename>.axf BIN(<filename>.bin)[3]

 

and we could check the binary with application(AN11305)[4].

this software will check the signature at 0x1C, (43 f0 ff ef or charater Cðÿï )

Reference

[1]http://www.keil.com/support/docs/3213.htm

[2]http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.faqs/ka11291.html

[3]http://www.lpcware.com/content/blog/binary-file-creation-using-keil-mdk-toolchain

[4]http://www.lpcware.com/content/nxpfile/an11305-usb-system-programming-lpc11u3xlpc11u2x