I've changed the ISR. i'm looking for start and stop.
if the character read it's not start i erase the location(of my_byte)
if it's start i increment the location
if it's stop i stop the interrupts (EA=0)



void intr (void) interrupt 2
{
port1=(~P1)&0x01;
my_byte[i]=my_byte[i]<<1;
my_byte[i]=my_byte[i]+port1; //writing bit in byte
nrb++; //increment number of bits
if (nrb==5){
if (have_start==0)//we don't have a START yet
{ if (my_byte[i]==0x1A) //have we found a start?
{
if (i<14)
{ i++; } //found start so increment i
have_start=1;
}
else //we don't have a start yet and this is not a start!
{

my_byte[i]=0x0; //we clear my byte
}
}
else //we read a start in the past
{
if (my_byte[i]==0x1F) //byte read not end sentinel
{
have_stop=1;
EA=0;
}
else{
if (i<14) {
i++; }
}
}
nrb=0; //set number of bits to 0
}
}

the results are sent to the PC with this:
while1:
c = _getkey ();

for(j=0;j<=i;j++)
{
putchar ( my_byte[j]+48);
my_byte[j]=0x0;
}

have_start=0;
have_stop=0;
nrb=0;
i=0;
EA=1; //start again the global intterupt service

goto while1;

the result is this
i = number of bytes ( locations in my_byte[])
(first 3 readings with a card, then with another card)
J is start sentinel and o is end sentinel
i can't explain what happend with readings 2,4,6,8

i:4 J1@=O
i:0 0
i:4 J1@=O
i:0 1
i:4 J112O
i:0 1
i:4 J112O
i:0 1