How to convert unsigned to signed char (and back) while preserving range in C? -



How to convert unsigned to signed char (and back) while preserving range in C? -

i have situation need convert unsigned char (0-255) signed char (-128-127). want have 0 converted -128, 127 converted 0 , 255 converted 127.

i using code (even though won't preserve range entirely):

unsigned char convertunsigned(char n) { homecoming n + 127; } char convertsigned(unsigned char n) { homecoming n - 127; }

this code appears taking values , converting them 255, can't verify (see below).

i writing vex pic microcontroller (which has microchip picmicro pic18f8520) using mplab c18 compiler. can't tell code doing because have no debugger or other way communicate code on chip.

the compiler supports c89 , not automatically promote operands ints (see the manual, section 2.7.1) normal c compilers, might part of problem.

update

the application writing works this:

get unsigned char represents joystick axis (255 = total forward, 0 = total backward, center = ~127/128 [the documentation not state specifically]) convert char using convertsigned(n) do math calculate motor speed (i have eliminated step testing). convert unsigned char motor (same range joystick, except documentation explicitly states center value 127), using convertunsigned(n).

i think want:

unsigned char convertunsigned(char n) { homecoming (int)n + 128; } char convertsigned(unsigned char n) { homecoming (int)n - 128; }

assuming "127 converted 0" typo.

c unsigned signed mplab

Comments

Post a Comment

Popular posts from this blog

Delphi change the assembly code of a running process -

Delphi change the assembly code of a running process - i'm trying alter address 00741fa5 has push test.009e721c . alter push test.009e71c8 . procedure callback; asm force $9e71c8 end; procedure tform2.btn1click(sender: tobject); var ppid :dword; pprocess : cardinal; begin getwindowthreadprocessid(findwindow(nil,pchar('test')), @ppid); pprocess := openprocess(process_all_access, false, ppid); injectasm(pprocess, $741fa5, 10, integer(@callback), 0); end; here injectasm function (with error checking) function injectasm(process: longword; injectaddress, injectsize, codeaddress, codesize : integer): pointer; var csize, rsize : integer; replaced : array of byte; jmp : array [0..4] of byte; jmpaddress : integer; nopv : byte; : integer; nbr: ulong_ptr; begin //injectsize must equal or greater 5, because need space our //(far) jmp wwxxyyzz instruction //if there's no space, inject in place of few instructions if injectsize ...
Read more

json - Hibernate and Jackson (java.lang.IllegalStateException: Cannot call sendError() after the response has been committed) -

json - Hibernate and Jackson (java.lang.IllegalStateException: Cannot call sendError() after the response has been committed) - hello have problem hibernate , jackson. have 2 pojos @entity @table(name = "users") public class user implements serializable { static final long serialversionuid = 4235637833262722256l; @id @generatedvalue private int id; @column(name = "creation_date") private date creationdate; @column(name = "first_name") private string firstname; @column(name = "last_name") private string lastname; @version @column(name = "version") private int version; @column(name = "e_mail") private string email; @column(name = "enabled") private boolean enabled; @column(name = "login") private string login; @column(name = "password") private string password; @jsonmanagedreference("role") @onetomany(mappedby = "user", cascade = cascadetype.all,fetch = fetchtyp...
Read more

C++ 11 "class" keyword -

C++ 11 "class" keyword - i've started using c++ 11 little bit more , have few questions on special uses of class keyword. know it's used declare class, there's 2 instances have seen don't understand: method<class t>(); and class class_name *var; why precede typename keyword class in first example, , keyword pointer in sec example? that known elaborated type specifier , necessary when class name "shadowed" or "hidden" , need explicit. class t { }; // love of god don't t t; t t2; if compiler smart, give these warnings: main.cpp:15:5: error: must utilize 'class' tag refer type 't' in scope t t2; ^ class main.cpp:14:7: note: class 't' hidden non-type declaration of 't' here t t; ^ if class not defined, deed forwards declaration. for example: template <typename t> void method() { using type = typename t::value_type; } method...
Read more