convert hex to interger

how do u convert the ascii hex input (from the buffer) into an integer???:crazy:

 

oh this is what i got for now

Code:

push ebp
mov ebp,esp
sub esp,36
push eax
push ebx
push ecx
push edx


mov esi,0    ;#chraracter count
lea edi,[ebp-35]

readchr:
mov eax,SYS_read
mov ebx,STDIN
lea ecx,[ebp-36]
mov edx,1
int 80h

mov  al,byte[ebp-36]
cmp al,LF
je readDone

cmp esi,35
jg readchr

mov byte[edi],al
inc esi
inc edi
jmp readchr

readDone:
mov byte[edi],NULL