def pin_handler(arg):
    print("got an interrupt in pin %s" %(arg.id()))

    pycom.rgbled(red)
    print("Sequence de lecture RFID !")

    rfid = UART(1, baudrate=9600, pins=('P16', 'P17'))
    rfid.init(baudrate=9600, bits=8, parity=None, stop=1, timeout_chars=2, pins=('P16', 'P17'), rx_buffer_size=2048)


    global uuid                 # = bytearray(16)
    rfid_power.value(1)         # Powering the RFID decoder via a power load
    time.sleep(0.5)
    uuid = rfid.read(17)        # first reading of the rfid decoder buffer for cleaning it

    
    time.sleep(0.5)             
    pycom.rgbled(orange)
           

    while True:
        uuid = rfid.read(17)     # reading of the buffer of the rfid buffer
        time.sleep(1)
        print('id = ', uuid)

        if uuid is not None:        # if buffer has something different than "None"
            global rfid_number
            print("   ID detected !")                    
            rfid_power.value(0)
            pycom.rgbled(green)     # led sequence for seeing that RFID number is detected
            time.sleep(0.1)
            pycom.rgbled(black)
            time.sleep(0.1)
            pycom.rgbled(green)
            time.sleep(0.1)
            pycom.rgbled(black)     
            time.sleep(0.1)
            pycom.rgbled(green)
            time.sleep(0.1)
            pycom.rgbled(black)
            time.sleep(0.1)
            pycom.rgbled(green)
            time.sleep(1.5)
            pycom.rgbled(black)
            rfid_number = uuid
            rfid.deinit()
            print(p_in.value())       # just to know the pin value for verification
            time.sleep(3)
            break                     # breaking the while function  

And the while (True): start with the p_in callback ( P10 ):

while (True):

    p_in = Pin('P10', mode=Pin.IN, pull=Pin.PULL_UP)
    p_in.callback(Pin.IRQ_RISING, pin_handler, arg = None)


    print(y)                                # comptage du nombre de transmission ( en minutes ) avant reset ( test )
    print("RFID", rfid_number[0:14])


    gps   = l76.coordinates()
    pitch = acc.pitch()
    accel = acc.acceleration()
    roll  = acc.roll()
    batt  = py.read_battery_voltage()
    rfid  = rfid_number[0:14]
    # TempA = sensor.read_ambiant_temp()
    # TempO = sensor.read_object_temp()

I use an rfid decoder (134.2Khz ) with uart output RDM660 TTL

Here is the terminal info:

1
got an interrupt in pin P10
Sequence de lecture RFID !
id =  None
id =  b'967000009112695\r\n'
   ID detected !
1
got an interrupt in pin P10
Sequence de lecture RFID !
id =  None
id =  b'967000009112695\r\n'
   ID detected !
3
RFID b'96700000911269'
(None, None) - (2021, 11, 30, 10, 9, 33, 345068, None) - 2531328
Gps:            (None, None)
Acceleration:   (-0.01611328, -0.00793457, 0.9969482)
Roll:           0.5656762
Pitch:          0.4559399
Batt Volt:      4.455878
Rfid:           b'96700000911269'
{"TIME": [2021, 11, 30, 10, 9, 33, 441458, null], "DATAS": {"ROLL": 0.5656762, "BATTERY": 4.455878, "ID": "96700000911269", "GPS": [null, null], "PITCH": 0.4559399, "ACCELERATION": [-0.01611328, -0.00793457, 0.9969482]}}
1
WIFI connected succesfully
SENDING PAYLOAD to NODERED
MQTTClient disconnected
WIFI disconnected ! 

got an interrupt in pin P10
Sequence de lecture RFID !
id =  None
id =  b'967000009112695\r\n'
   ID detected !
1
got an interrupt in pin P10
Sequence de lecture RFID !
id =  None
id =  b'967000009112695\r\n'
   ID detected !
1

"1" alone, is the value of the pin(P10).
You can see that the rfid value is ok in the sequence so the while function must break !
Sometime it break at the first occurence and sometime it need 8 occurences before breaking !

Thanks in advance for helping.
Best regards
Jiemde

On a side note: I would not create the UART object in the callback over and over again. You can create if beforehand and store the object in a global variable. You would have to declare that in the callback as global, otherwise it is not visible.
Besides that, P16 and P17 are input only pins. You cannot use them for UART TX. But you do not write to UART in your code, so it might be fine. Better add an external pull-up resistor to the TX pin.

Question: what solution to adopt? - debouncing hardware or software?
What is the solution adopted on the expansion board 3.1 for the "S1" button ?

Indeed I only use uart reception. it works great, however i will heed your suggestion of external resistance.