示例#1
0
def reset_modem(lte: LTE, debug_print=False):
    function_level = "1"
    cereg_level = "0"

    if debug_print: print("\twaiting for reset to finish")
    lte.reset()
    lte.init()

    if debug_print: print("\tsetting function level")
    for tries in range(5):
        _send_at_cmd(lte, "AT+CFUN=" + function_level)
        result = _send_at_cmd(lte, "AT+CFUN?")
        if result[0] == '+CFUN: ' + function_level:
            break
    else:
        raise Exception("could not set modem function level")

    if debug_print: print("\twaiting for SIM to be responsive")
    for tries in range(10):
        result = _send_at_cmd(lte, "AT+CIMI")
        if result[-1] == 'OK':
            break
    else:
        raise Exception("SIM does not seem to respond after reset")

    if debug_print: print("\tdisabling CEREG messages")
    # we disable unsolicited CEREG messages, as they interfere with AT communication with the SIM via CSIM commands
    # this also requires to use an attach method that does not require cereg messages, for pycom that is legacyattach=false
    for tries in range(5):
        _send_at_cmd(lte, "AT+CEREG=" + cereg_level)
        result = _send_at_cmd(lte, "AT+CEREG?")
        if result[0][0:9] == '+CEREG: ' + cereg_level:
            break
    else:
        raise Exception("could not set CEREG level")
示例#2
0
def check_OTA_update():
    # Configuration (if you are looking for the server pubkey: it's in the OTA class)
    #TODO: Change server URL and Pubkey to non-testing versions
    SERVER_URL = "ota.iot.wheelmap.pro"
    SERVER_PORT = 80
    NBIOT_APN = "iot.1nce.net"
    NBIOT_BAND = None  #None = autoscan
    NBIOT_ATTACH_TIMEOUT = 15 * 60  #seconds
    NBIOT_CONNECT_TIMEOUT = 15 * 60  #seconds
    WATCHDOG_TIMEOUT = 15 * 60 * 1000  #milliseconds

    #setup watchdog
    wdt = machine.WDT(timeout=WATCHDOG_TIMEOUT)
    wdt.feed()

    #initialize ota object variable for proper exception handling
    ota = None

    try:
        # # Setup Wifi OTA
        # from ota_wifi_secrets import WIFI_SSID, WIFI_PW
        # ota = WiFiOTA(WIFI_SSID,
        #         WIFI_PW)

        # Setup NB-IoT OTA
        print("Initializing LTE")
        lte = LTE()
        lte.reset()
        lte.init()

        ota = NBIoTOTA(lte, NBIOT_APN, NBIOT_BAND, NBIOT_ATTACH_TIMEOUT,
                       NBIOT_CONNECT_TIMEOUT)

        #start the update itself
        print("Current version: ", ota.get_current_version())
        ota.connect(url=SERVER_URL, port=SERVER_PORT)
        ota.update()

        # the update did not fail, proceed to check file integrity
        n = ota.check_stored_files()

        if n > 0:
            print("%d corrupted files detected and reloaded! Rebooting ..." %
                  n)

            time.sleep(0.5)
            machine.reset()
    except Exception as e:
        raise (e)  #let top level loop handle exception
    finally:
        if ota is not None:
            ota.clean_up()
        # before leaving, set watchdog to large value, so we don't interfere
        # with code in main.py (wdt can never be disabled after use)
        wdt = machine.WDT(timeout=10 * 24 * 60 * 60 * 1000)
        wdt.feed()
示例#3
0
class StartIoT:
  def __init__(self, network=LTE_M):
    self._network = network
    self.lte = LTE()
    try:
      self.lte.deinit()
      self.lte.reset()
    except:
      pass
    sleep(5)

    self.lte.init()
    sleep(5)

    self._assure_modem_fw()

  def _assure_modem_fw(self):
    response = self.lte.send_at_cmd('ATI1')
    if response != None:
      lines = response.split('\r\n')
      fw_id = lines[1][0:3]
      is_nb = fw_id == 'UE6'
      if is_nb:
        print('Modem is using NB-IoT firmware (%s/%s).' % (lines[1], lines[2]))
      else:
        print('Modem in using LTE-M firmware (%s/%s).' % (lines[1], lines[2]))
      if not is_nb and self._network == NB_IOT:
        print('You cannot connect using NB-IoT with wrong modem firmware! Please re-flash the modem with the correct firmware.')
        raise WrongNetwork
      if is_nb and self._network == LTE_M:
        print('You cannot connect using LTE-M with wrong modem firmware! Please re-flash the modem with the correct firmware.')
        raise WrongNetwork
    else:
      print('Failed to determine modem firmware. Rebooting device...')
      reset() # Reboot the device


  def send_at_cmd_pretty(self, cmd):
    print('>', cmd)
    response = self.lte.send_at_cmd(cmd)
    if response != None:
      lines = response.split('\r\n')
      for line in lines:
        if len(line.strip()) != 0:
          print('>>', line)
    else:
      print('>> No response.')
    return response

  def connect(self):
    # NB-IoT
    if (self._network == NB_IOT):
      self.send_at_cmd_pretty('AT+CFUN=0')
      self.send_at_cmd_pretty('AT+CEMODE=0')
      self.send_at_cmd_pretty('AT+CEMODE?')
      self.send_at_cmd_pretty('AT!="clearscanconfig"')
      self.send_at_cmd_pretty('AT!="addscanfreq band=%s dl-earfcn=%s"' % (BAND, EARFCN))
      self.send_at_cmd_pretty('AT+CGDCONT=1,"IP","%s"' % APN)
      self.send_at_cmd_pretty('AT+COPS=1,2,"%s"' % COPS)
      self.send_at_cmd_pretty('AT+CFUN=1')

    # LTE-M (Cat M1)
    else:
      self.send_at_cmd_pretty('AT+CFUN=0')
      self.send_at_cmd_pretty('AT!="clearscanconfig"')
      self.send_at_cmd_pretty('AT!="addscanfreq band=%s dl-earfcn=%s"' % (BAND, EARFCN))
      self.send_at_cmd_pretty('AT+CGDCONT=1,"IP","%s"' % APN)
      self.send_at_cmd_pretty('AT+CFUN=1')
      self.send_at_cmd_pretty('AT+CSQ')

    # For a range scan:
    # AT!="addscanfreqrange band=20 dl-earfcn-min=3450 dl-earfcn-max=6352"

    print('Attaching...')
    seconds = 0
    while not self.lte.isattached() and seconds < attach_timeout:
      sleep(0.25)
      seconds += 0.25
    if self.lte.isattached():
      print('Attached!')
    else:
      print('Failed to attach to LTE (timeout)!')
      raise AttachTimeout
    self.lte.connect()

    print('Connecting...')
    seconds = 0
    while not self.lte.isconnected() and seconds < connect_timeout:
      sleep(0.25)
      seconds += 0.25
    if self.lte.isconnected():
      print('Connected!')
    else:
      print('Failed to connect to LTE (timeout)!')
      raise ConnectTimeout

  def disconnect(self):
    if self.lte.isconnected():
      self.lte.disconnect()

  def dettach(self):
    if self.lte.isattached():
      self.lte.dettach()
class LteComms:
    def __init__(self):
        self.message_storage = 'AT+CPMS="SM", "SM", "SM"'
        gc.collect()
        try:
            self.lte = LTE()
            time.sleep(4)
        except:
            print("initialize LTE object?")
        self.lte.reset()
        time.sleep(4)
        print("delay 4 secs")

    def at(self, cmd):
        print("modem command: {}".format(cmd))
        r = self.lte.send_at_cmd(cmd).split('\r\n')
        r = list(filter(None, r))
        print("response={}".format(r))
        return r

    def attach_LTE(self):
        gc.collect()
        time.sleep(10.0)

        if self.lte.isattached():
            try:
                print("LTE was already attached, disconnecting...")
                if self.lte.isconnected():
                    print("disconnect")
                    self.lte.disconnect()
            except:
                print("Exception during disconnect")

            try:
                if self.lte.isattached():
                    print("detach")
                    self.lte.dettach()
            except:
                print("Exception during dettach")

            try:
                print("resetting modem...")
                self.lte.reset()
            except:
                print("Exception during reset")

            print("delay 5 secs")
            time.sleep(5.0)

        # enable network registration and location information, unsolicited result code
        self.at('AT+CEREG=2')

        # print("full functionality level")
        self.at('AT+CFUN=1')
        time.sleep(1.0)

        # using Hologram SIM
        self.at('AT+CGDCONT=1,"IP","hologram"')

        print("attempt to attach cell modem to base station...")
        # lte.attach()  # do not use attach with custom init for Hologram SIM

        self.at("ATI")
        time.sleep(2.0)

        i = 0
        while self.lte.isattached() == False:
            # get EPS Network Registration Status:
            # +CEREG: <stat>[,[<tac>],[<ci>],[<AcT>]]
            # <tac> values:
            # 0 - not registered
            # 1 - registered, home network
            # 2 - not registered, but searching...
            # 3 - registration denied
            # 4 - unknown (out of E-UTRAN coverage)
            # 5 - registered, roaming
            r = self.at('AT+CEREG?')
            try:
                r0 = r[0]  # +CREG: 2,<tac>
                r0x = r0.split(',')  # ['+CREG: 2',<tac>]
                tac = int(r0x[1])  # 0..5
                print("tac={}".format(tac))
            except IndexError:
                tac = 0
                print("Index Error!!!")

            # get signal strength
            # +CSQ: <rssi>,<ber>
            # <rssi>: 0..31, 99-unknown
            r = self.at('AT+CSQ')

            # extended error report
            # r =self.at('AT+CEER')

            # if lte.isattached():
            #    print("Modem attached (isattached() function worked)!!!")
            #    break

            # if (tac==1) or (tac==5):
            #    print("Modem attached!!!")
            #    break

            i = i + 5
            print("not attached: {} secs".format(i))

        # while self.lte.isattached():
        #     # self.receive_and_forward_to_chat()
        #     continue
        # print("Modem not attached")
        print("set to check messages on sim")
        self.at(self.message_storage)

    def connect_lte_data(self):
        self.at('AT+CEREG?')
        print("Attempt to connect")
        if self.lte.isattached() == False:
            print("Not attached, try again, will fail")
        else:
            print("Attached and continue")

        self.lte.connect()
        i = 0
        while not self.lte.isconnected():
            i = i + 1
            print("not connected: {}".format(i))
            time.sleep(1.0)

        print("LTE connected for data!!!")  # also send this to chat
        # so just pymesh this to all nodes in leader_mesh_list
        while self.lte.isconnected():
            continue

    def scrape_webpage(self, url):
        s = socket.socket()
        s = ssl.wrap_socket(s)
        s.connect(socket.getaddrinfo(url, 443)[0][-1])
        s.send(b"GET / HTTP/1.0\r\n\r\n")
        print(s.recv(4096))
        s.close()

    def send_sms(self, number, msg):
        # this will somehow have to be connected to the chat with a JM msg1
        print("set mode to text")
        self.at('AT+CMGF=1')
        time.sleep(.5)
        # msg = ('AT+CMGS="%s"\r%s\0x1a' % (number, msg))
        # print(('ATTB+SQNSMSSEND="%s", "%s"' % (number, msg)))
        print('sendin an sms', end=' ')
        ans = self.lte.send_at_cmd(
            ('AT+SQNSMSSEND="%s", "%s"' % (number, msg))).split('\r\n')
        print(ans)
        # self.at(msg)
        time.sleep(4)
        print("sent!")

    def receive_and_forward_to_chat(self):
        # this will somehow have to be connected to the chat with a JM msg1
        print("set mode to text")
        self.at('AT+CMGF=1')
        msg_list = []
        msg_list = self.at('AT+CMGL="ALL"')
        number_of_messages = 0
        if len(msg_list) > 1:
            print("This'll print if there a msg")
            if len(msg_list) > 20:
                print("More then 10 messages, loop")
                i = 1
                while len(msg_list) > 20:
                    print("This is the inner loop running %s times" % i)
                    msg_list = self.at('AT+CMGL="ALL"')
                    number_of_messages += len(msg_list)
                    self.write_msg_to_file_and_delete(msg_list)
                    time.sleep(15)
                    i += 1
                print("This is to get the last group of messages")
                # you don't scan for messages while it sleep, almost Need
                # to run this in a thread in the background.
                time.sleep(10)
                msg_list = self.at('AT+CMGL="ALL"')
                number_of_messages += len(msg_list)
                self.write_msg_to_file_and_delete(msg_list)
            else:
                print("The list is less than 10, so straight to file")
                number_of_messages += len(msg_list)
                self.write_msg_to_file_and_delete(msg_list)
        else:
            print("This prints when no messages")
            self.at('AT+CMGD=1,4')
        # Cuz apparently you need to clean out the sim card, it only holds 10 msgs
        # at('AT+CMGD=1,4')
        time.sleep(5)
        actual_messages = (number_of_messages / 2) - 1
        print(actual_messages)

    def msg_parse(self, msg_list):
        parsed_msg_list = []
        msg_list_string = "".join(msg_list)
        split_msg_list = msg_list_string.split('+CMGL:')
        for i in range(len(split_msg_list)):
            temp_string = str(split_msg_list[i])
            if temp_string[-2:] == 'OK':
                parsed_msg_list.append(temp_string[:-2])
            else:
                parsed_msg_list.append(temp_string)
        return parsed_msg_list

    def disconnect_LTE(self):
        self.lte.disconnect()
        print("LTE Data disconnected")
        # send to chat

    def unattach_lte(self):
        self.lte.detach(reset=True)
        print("LTE modem deattached")

    def signal_strength(self):
        self.at('AT+CSQ')

    def check_read_sms(self):
        self.at('AT+CMGF=1')
        msg_list = self.at('AT+CMGL="ALL"')
        print(msg_list)

    def write_msg_to_file_and_delete(self, msg_list):
        parsed_msg_list = self.msg_parse(msg_list)
        print("Writing to SMS log")
        f = open('/sd/www/sms.txt', 'a+')
        for i in range(len(parsed_msg_list)):
            if parsed_msg_list[i] != '\r\n':
                f.write(str(parsed_msg_list[i]))
                f.write('\r\n')
        f.close()
        self.at('AT+CMGD=1,4')
示例#5
0
# r = input("Enter anything to abort...")  # allow opportunity to stop program
# if r != "":
#    sys.exit(0)

print("disable MicroPython control of LED")
pycom.heartbeat(False)
pycom.rgbled(WHITE)

print("instantiate LTE object")
lte = LTE(carrier="verizon")
print("delay 4 secs")
time.sleep(4.0)

print("reset modem")
try:
    lte.reset()
except:
    print("Exception during reset")

print("delay 5 secs")
time.sleep(5.0)

if lte.isattached():
    try:
        print("LTE was already attached, disconnecting...")
        if lte.isconnected():
            print("disconnect")
            lte.disconnect()
    except:
        print("Exception during disconnect")
示例#6
0
class StartIoT:
    def __init__(self, network=LTE_M):
        self._network = network
        self.lte = LTE()
        try:
            self.lte.deinit()
            self.lte.reset()
        except:
            pass
        sleep(5)

        self.lte.init()
        sleep(5)

        self._assure_modem_fw()

    def _assure_modem_fw(self):
        response = self.lte.send_at_cmd('ATI1')
        if response != None:
            lines = response.split('\r\n')
            fw_id = lines[1][0:3]
            is_nb = fw_id == 'UE6'
            if is_nb:
                print('Modem is using NB-IoT firmware (%s/%s).' %
                      (lines[1], lines[2]))
            else:
                print('Modem in using LTE-M firmware (%s/%s).' %
                      (lines[1], lines[2]))
            if not is_nb and self._network == NB_IOT:
                print(
                    'You cannot connect using NB-IoT with wrong modem firmware! Please re-flash the modem with the correct firmware.'
                )
                raise WrongNetwork
            if is_nb and self._network == LTE_M:
                print(
                    'You cannot connect using LTE-M with wrong modem firmware! Please re-flash the modem with the correct firmware.'
                )
                raise WrongNetwork
        else:
            print('Failed to determine modem firmware. Rebooting device...')
            reset()  # Reboot the device

    def _get_assigned_ip(self):
        ip_address = None
        try:
            self.lte.pppsuspend()
            response = self.send_at_cmd_pretty('AT+CGPADDR=1')
            self.lte.pppresume()
            lines = response.split('\r\n')
            sections = lines[1].split('"')
            ip_address = sections[1]
        except:
            print('Failed to retrieve assigned IP from LTE network.')

        return ip_address

    def send_at_cmd_pretty(self, cmd):
        print('>', cmd)
        response = self.lte.send_at_cmd(cmd)
        if response != None:
            lines = response.split('\r\n')
            for line in lines:
                if len(line.strip()) != 0:
                    print('>>', line)
        else:
            print('>> No response.')
        return response

    def connect(self):
        # NB-IoT
        if (self._network == NB_IOT):
            self.send_at_cmd_pretty('AT+CFUN=0')
            self.send_at_cmd_pretty('AT+CEMODE=0')
            self.send_at_cmd_pretty('AT+CEMODE?')
            self.send_at_cmd_pretty('AT!="clearscanconfig"')
            self.send_at_cmd_pretty('AT!="addscanfreq band=%s dl-earfcn=%s"' %
                                    (BAND, EARFCN))
            self.send_at_cmd_pretty('AT+CGDCONT=1,"IP","%s"' % APN)
            self.send_at_cmd_pretty('AT+COPS=1,2,"%s"' % COPS)
            self.send_at_cmd_pretty('AT+CFUN=1')

        # LTE-M (Cat M1)
        else:
            self.send_at_cmd_pretty('AT+CFUN=0')
            self.send_at_cmd_pretty('AT!="clearscanconfig"')
            self.send_at_cmd_pretty('AT!="addscanfreq band=%s dl-earfcn=%s"' %
                                    (BAND, EARFCN))
            self.send_at_cmd_pretty('AT+CGDCONT=1,"IP","%s"' % APN)
            self.send_at_cmd_pretty('AT+CFUN=1')
            self.send_at_cmd_pretty('AT+CSQ')

        # For a range scan:
        # AT!="addscanfreqrange band=20 dl-earfcn-min=3450 dl-earfcn-max=6352"

        print('Attaching...')
        seconds = 0
        while not self.lte.isattached() and seconds < attach_timeout:
            sleep(0.25)
            seconds += 0.25
        if self.lte.isattached():
            print('Attached!')
        else:
            print('Failed to attach to LTE (timeout)!')
            raise AttachTimeout
        self.lte.connect()

        print('Connecting...')
        seconds = 0
        while not self.lte.isconnected() and seconds < connect_timeout:
            sleep(0.25)
            seconds += 0.25
        if self.lte.isconnected():
            print('Connected!')
        else:
            print('Failed to connect to LTE (timeout)!')
            raise ConnectTimeout

        print('Retrieving assigned IP...')
        ip_address = self._get_assigned_ip()

        print("Device IP: {}".format(ip_address))
        print(ip_address)

        # Initialise the CoAP module
        Coap.init(ip_address)

        # Register the response handler for the requests that the module initiates as a CoAP Client
        Coap.register_response_handler(self.response_callback)

        # A CoAP server is needed if CoAP push is used (messages are pushed down from Managed IoT Cloud)
        # self.setup_coap_server()

    def setup_coap_server(self):
        # Add a resource with a default value and a plain text content format
        r = Coap.add_resource('',
                              media_type=Coap.MEDIATYPE_APP_JSON,
                              value='default_value')
        # Configure the possible operations on the resource
        r.callback(
            Coap.REQUEST_GET | Coap.REQUEST_POST | Coap.REQUEST_PUT
            | Coap.REQUEST_DELETE, True)

        # Get the UDP socket created for the CoAP module
        coap_server_socket = Coap.socket()
        # Create a new poll object
        p = uselect.poll()
        # Register the CoAP module's socket to the poll
        p.register(coap_server_socket,
                   uselect.POLLIN | uselect.POLLHUP | uselect.POLLERR)
        # Start a new thread which will handle the sockets of "p" poll
        _thread.start_new_thread(socket_thread, (p, coap_server_socket))

        print('CoAP server running!')

    # The callback that handles the responses generated from the requests sent to a CoAP Server
    def response_callback(self, code, id_param, type_param, token, payload):
        # The ID can be used to pair the requests with the responses
        print('ID: {}'.format(id_param))
        print('Code: {}'.format(code))
        print('Type: {}'.format(type_param))
        print('Token: {}'.format(token))
        print('Payload: {}'.format(payload))

    def disconnect(self):
        if self.lte.isconnected():
            self.lte.disconnect()

    def dettach(self):
        if self.lte.isattached():
            self.lte.dettach()

    def send(self, data):
        if not self.lte.isconnected():
            raise Exception('Not connected! Unable to send.')

        id = Coap.send_request(IOTGW_IP,
                               Coap.REQUEST_POST,
                               uri_port=IOTGW_PORT,
                               uri_path=IOTGW_ENDPOINT,
                               payload=data,
                               include_options=True)
        print('CoAP POST message ID: {}'.format(id))

    def pull(self, uri_path='/'):
        if not self.lte.isconnected():
            raise Exception('Not connected! Unable to pull.')

        id = Coap.send_request(IOTGW_IP,
                               Coap.REQUEST_GET,
                               uri_port=IOTGW_PORT,
                               uri_path=uri_path,
                               include_options=True)
        Coap.read()
        print('CoAP GET message ID: {}'.format(id))
class NanoGateway:
    """
    Nano gateway class, set up by default for use with TTN, but can be configured
    for any other network supporting the Semtech Packet Forwarder.
    Only required configuration is wifi_ssid and wifi_password which are used for
    connecting to the Internet.
    """
    def __init__(self,
                 id,
                 frequency,
                 datarate,
                 server,
                 port,
                 ntp_server='pool.ntp.org',
                 ntp_period=3600):
        self.id = id
        self.server = server
        self.port = port

        self.frequency = frequency
        self.datarate = datarate

        # self.ssid = ssid
        # self.password = password

        self.ntp_server = ntp_server
        self.ntp_period = ntp_period

        self.server_ip = None

        self.rxnb = 0
        self.rxok = 0
        self.rxfw = 0
        self.dwnb = 0
        self.txnb = 0

        self.sf = self._dr_to_sf(self.datarate)
        self.bw = self._dr_to_bw(self.datarate)

        self.stat_alarm = None
        self.pull_alarm = None
        self.uplink_alarm = None

        self.lte = None
        self.sock = None
        self.udp_stop = False
        self.udp_lock = _thread.allocate_lock()

        self.lora = None
        self.lora_sock = None

        self.rtc = machine.RTC()

    def start(self):
        """
        Starts the LoRaWAN nano gateway.
        """

        pycom.heartbeat(False)

        self._log('Starting LoRaWAN nano gateway with id: {}', self.id)

        # # setup WiFi as a station and connect
        # self.wlan = WLAN(mode=WLAN.STA)
        # self._connect_to_wifi()

        # setup LTE CATM1 connection
        self.lte = LTE(carrier="verizon")
        self._connect_to_LTE()

        # get a time sync
        self._log('Syncing time with {} ...', self.ntp_server)
        self.rtc.ntp_sync(self.ntp_server, update_period=self.ntp_period)
        while not self.rtc.synced():
            utime.sleep_ms(50)
        self._log("RTC NTP sync complete")

        # get the server IP and create an UDP socket
        self.server_ip = usocket.getaddrinfo(self.server, self.port)[0][-1]
        self._log('Opening UDP socket to {} ({}) port {}...', self.server,
                  self.server_ip[0], self.server_ip[1])
        self.sock = usocket.socket(usocket.AF_INET, usocket.SOCK_DGRAM,
                                   usocket.IPPROTO_UDP)
        self.sock.setsockopt(usocket.SOL_SOCKET, usocket.SO_REUSEADDR, 1)
        self.sock.setblocking(False)

        # push the first time immediatelly
        self._push_data(self._make_stat_packet())

        # create the alarms
        self.stat_alarm = Timer.Alarm(
            handler=lambda t: self._push_data(self._make_stat_packet()),
            s=60,
            periodic=True)
        self.pull_alarm = Timer.Alarm(handler=lambda u: self._pull_data(),
                                      s=25,
                                      periodic=True)

        # start the UDP receive thread
        self.udp_stop = False
        _thread.start_new_thread(self._udp_thread, ())

        # initialize the LoRa radio in LORA mode
        self._log('Setting up the LoRa radio at {} Mhz using {}',
                  self._freq_to_float(self.frequency), self.datarate)
        self.lora = LoRa(mode=LoRa.LORA,
                         frequency=self.frequency,
                         bandwidth=self.bw,
                         sf=self.sf,
                         preamble=8,
                         coding_rate=LoRa.CODING_4_5,
                         tx_iq=True)

        # create a raw LoRa socket
        self.lora_sock = usocket.socket(usocket.AF_LORA, usocket.SOCK_RAW)
        self.lora_sock.setblocking(False)
        self.lora_tx_done = False

        self.lora.callback(trigger=(LoRa.RX_PACKET_EVENT
                                    | LoRa.TX_PACKET_EVENT),
                           handler=self._lora_cb)
        self._log('LoRaWAN nano gateway online')

    def stop(self):
        """
        Stops the LoRaWAN nano gateway.
        """

        self._log('Stopping...')

        # send the LoRa radio to sleep
        self.lora.callback(trigger=None, handler=None)
        self.lora.power_mode(LoRa.SLEEP)

        # stop the NTP sync
        self.rtc.ntp_sync(None)

        # cancel all the alarms
        self.stat_alarm.cancel()
        self.pull_alarm.cancel()

        # signal the UDP thread to stop
        self.udp_stop = True
        while self.udp_stop:
            utime.sleep_ms(50)

        # disable LTE
        self.lte.disconnect()
        self.lte.dettach()

    def _connect_to_wifi(self):
        self.wlan.connect(self.ssid, auth=(None, self.password))
        while not self.wlan.isconnected():
            utime.sleep_ms(50)
        self._log('WiFi connected to: {}', self.ssid)

    def _connect_to_LTE(self):
        print("reset modem")
        try:
            self.lte.reset()
        except:
            print("Exception during reset")

        print("delay 5 secs")
        utime.sleep(5.0)

        if self.lte.isattached():
            try:
                print("LTE was already attached, disconnecting...")
                if self.lte.isconnected():
                    print("disconnect")
                    self.lte.disconnect()
            except:
                print("Exception during disconnect")

            try:
                if self.lte.isattached():
                    print("detach")
                    self.lte.dettach()
            except:
                print("Exception during dettach")

            try:
                print("resetting modem...")
                self.lte.reset()
            except:
                print("Exception during reset")

            print("delay 5 secs")
            utime.sleep(5.0)

        # enable network registration and location information, unsolicited result code
        self.at('AT+CEREG=2')

        # print("full functionality level")
        self.at('AT+CFUN=1')
        utime.sleep(1.0)

        # using Hologram SIM
        self.at('AT+CGDCONT=1,"IP","hologram"')

        print("attempt to attach cell modem to base station...")
        # lte.attach()  # do not use attach with custom init for Hologram SIM

        self.at("ATI")
        utime.sleep(2.0)

        i = 0
        while self.lte.isattached() == False:
            # get EPS Network Registration Status:
            # +CEREG: <stat>[,[<tac>],[<ci>],[<AcT>]]
            # <tac> values:
            # 0 - not registered
            # 1 - registered, home network
            # 2 - not registered, but searching...
            # 3 - registration denied
            # 4 - unknown (out of E-UTRAN coverage)
            # 5 - registered, roaming
            r = self.at('AT+CEREG?')
            try:
                r0 = r[0]  # +CREG: 2,<tac>
                r0x = r0.split(',')  # ['+CREG: 2',<tac>]
                tac = int(r0x[1])  # 0..5
                print("tac={}".format(tac))
            except IndexError:
                tac = 0
                print("Index Error!!!")

            # get signal strength
            # +CSQ: <rssi>,<ber>
            # <rssi>: 0..31, 99-unknown
            r = self.at('AT+CSQ')

            # extended error report
            # r = at('AT+CEER')

            if self.lte.isattached():
                print("Modem attached (isattached() function worked)!!!")
                break

            if (tac == 1) or (tac == 5):
                print("Modem attached!!!")
                break

            i = i + 5
            print("not attached: {} secs".format(i))

            if (tac != 0):
                self.blink(BLUE, tac)
            else:
                self.blink(RED, 5)

            utime.sleep(2)

        self.at('AT+CEREG?')
        print("connect: start a data session and obtain an IP address")
        self.lte.connect(cid=3)
        i = 0
        while not self.lte.isconnected():
            i = i + 1
            print("not connected: {}".format(i))
            self.blink(YELLOW, 1)
            utime.sleep(1.0)

        print("connected!!!")
        pycom.rgbled(GREEN)

    def _dr_to_sf(self, dr):
        sf = dr[2:4]
        if sf[1] not in '0123456789':
            sf = sf[:1]
        return int(sf)

    def _dr_to_bw(self, dr):
        bw = dr[-5:]
        if bw == 'BW125':
            return LoRa.BW_125KHZ
        elif bw == 'BW250':
            return LoRa.BW_250KHZ
        else:
            return LoRa.BW_500KHZ

    def _sf_bw_to_dr(self, sf, bw):
        dr = 'SF' + str(sf)
        if bw == LoRa.BW_125KHZ:
            return dr + 'BW125'
        elif bw == LoRa.BW_250KHZ:
            return dr + 'BW250'
        else:
            return dr + 'BW500'

    def _lora_cb(self, lora):
        """
        LoRa radio events callback handler.
        """

        events = lora.events()
        if events & LoRa.RX_PACKET_EVENT:
            self.rxnb += 1
            self.rxok += 1
            rx_data = self.lora_sock.recv(256)
            stats = lora.stats()
            packet = self._make_node_packet(rx_data, self.rtc.now(),
                                            stats.rx_timestamp, stats.sfrx,
                                            self.bw, stats.rssi, stats.snr)
            self._push_data(packet)
            self._log('Received packet: {}', packet)
            self.rxfw += 1
        if events & LoRa.TX_PACKET_EVENT:
            self.txnb += 1
            lora.init(mode=LoRa.LORA,
                      frequency=self.frequency,
                      bandwidth=self.bw,
                      sf=self.sf,
                      preamble=8,
                      coding_rate=LoRa.CODING_4_5,
                      tx_iq=True)

    def _freq_to_float(self, frequency):
        """
        MicroPython has some inprecision when doing large float division.
        To counter this, this method first does integer division until we
        reach the decimal breaking point. This doesn't completely elimate
        the issue in all cases, but it does help for a number of commonly
        used frequencies.
        """

        divider = 6
        while divider > 0 and frequency % 10 == 0:
            frequency = frequency // 10
            divider -= 1
        if divider > 0:
            frequency = frequency / (10**divider)
        return frequency

    def _make_stat_packet(self):
        now = self.rtc.now()
        STAT_PK["stat"]["time"] = "%d-%02d-%02d %02d:%02d:%02d GMT" % (
            now[0], now[1], now[2], now[3], now[4], now[5])
        STAT_PK["stat"]["rxnb"] = self.rxnb
        STAT_PK["stat"]["rxok"] = self.rxok
        STAT_PK["stat"]["rxfw"] = self.rxfw
        STAT_PK["stat"]["dwnb"] = self.dwnb
        STAT_PK["stat"]["txnb"] = self.txnb
        return ujson.dumps(STAT_PK)

    def _make_node_packet(self, rx_data, rx_time, tmst, sf, bw, rssi, snr):
        RX_PK["rxpk"][0]["time"] = "%d-%02d-%02dT%02d:%02d:%02d.%dZ" % (
            rx_time[0], rx_time[1], rx_time[2], rx_time[3], rx_time[4],
            rx_time[5], rx_time[6])
        RX_PK["rxpk"][0]["tmst"] = tmst
        RX_PK["rxpk"][0]["freq"] = self._freq_to_float(self.frequency)
        RX_PK["rxpk"][0]["datr"] = self._sf_bw_to_dr(sf, bw)
        RX_PK["rxpk"][0]["rssi"] = rssi
        RX_PK["rxpk"][0]["lsnr"] = snr
        RX_PK["rxpk"][0]["data"] = ubinascii.b2a_base64(rx_data)[:-1]
        RX_PK["rxpk"][0]["size"] = len(rx_data)
        return ujson.dumps(RX_PK)

    def _push_data(self, data):
        token = uos.urandom(2)
        packet = bytes([PROTOCOL_VERSION]) + token + bytes(
            [PUSH_DATA]) + ubinascii.unhexlify(self.id) + data
        with self.udp_lock:
            try:
                self.sock.sendto(packet, self.server_ip)
            except Exception as ex:
                self._log('Failed to push uplink packet to server: {}', ex)

    def _pull_data(self):
        token = uos.urandom(2)
        packet = bytes([PROTOCOL_VERSION]) + token + bytes(
            [PULL_DATA]) + ubinascii.unhexlify(self.id)
        with self.udp_lock:
            try:
                self.sock.sendto(packet, self.server_ip)
            except Exception as ex:
                self._log('Failed to pull downlink packets from server: {}',
                          ex)

    def _ack_pull_rsp(self, token, error):
        TX_ACK_PK["txpk_ack"]["error"] = error
        resp = ujson.dumps(TX_ACK_PK)
        packet = bytes([PROTOCOL_VERSION]) + token + bytes(
            [PULL_ACK]) + ubinascii.unhexlify(self.id) + resp
        with self.udp_lock:
            try:
                self.sock.sendto(packet, self.server_ip)
            except Exception as ex:
                self._log('PULL RSP ACK exception: {}', ex)

    def _send_down_link(self, data, tmst, datarate, frequency):
        """
        Transmits a downlink message over LoRa.
        """

        self.lora.init(mode=LoRa.LORA,
                       frequency=frequency,
                       bandwidth=self._dr_to_bw(datarate),
                       sf=self._dr_to_sf(datarate),
                       preamble=8,
                       coding_rate=LoRa.CODING_4_5,
                       tx_iq=True)
        while utime.ticks_cpu() < tmst:
            pass
        self.lora_sock.send(data)
        self._log(
            'Sent downlink packet scheduled on {:.3f}, at {:.3f} Mhz using {}: {}',
            tmst / 1000000, self._freq_to_float(frequency), datarate, data)

    def _udp_thread(self):
        """
        UDP thread, reads data from the server and handles it.
        """

        while not self.udp_stop:
            try:
                data, src = self.sock.recvfrom(1024)
                _token = data[1:3]
                _type = data[3]
                if _type == PUSH_ACK:
                    self._log("Push ack")
                elif _type == PULL_ACK:
                    self._log("Pull ack")
                elif _type == PULL_RESP:
                    self.dwnb += 1
                    ack_error = TX_ERR_NONE
                    tx_pk = ujson.loads(data[4:])
                    tmst = tx_pk["txpk"]["tmst"]
                    t_us = tmst - utime.ticks_cpu() - 15000
                    if t_us < 0:
                        t_us += 0xFFFFFFFF
                    if t_us < 20000000:
                        self.uplink_alarm = Timer.Alarm(
                            handler=lambda x: self._send_down_link(
                                ubinascii.a2b_base64(tx_pk["txpk"]["data"]),
                                tx_pk["txpk"]["tmst"] - 50, tx_pk["txpk"][
                                    "datr"],
                                int(tx_pk["txpk"]["freq"] * 1000) * 1000),
                            us=t_us)
                    else:
                        ack_error = TX_ERR_TOO_LATE
                        self._log('Downlink timestamp error!, t_us: {}', t_us)
                    self._ack_pull_rsp(_token, ack_error)
                    self._log("Pull rsp")
            except usocket.timeout:
                pass
            except OSError as ex:
                if ex.errno != errno.EAGAIN:
                    self._log('UDP recv OSError Exception: {}', ex)
            except Exception as ex:
                self._log('UDP recv Exception: {}', ex)

            # wait before trying to receive again
            utime.sleep_ms(UDP_THREAD_CYCLE_MS)

        # we are to close the socket
        self.sock.close()
        self.udp_stop = False
        self._log('UDP thread stopped')

    def _log(self, message, *args):
        """
        Outputs a log message to stdout.
        """

        print('[{:>10.3f}] {}'.format(utime.ticks_ms() / 1000,
                                      str(message).format(*args)))

    def at(self, cmd):
        print("modem command: {}".format(cmd))
        r = self.lte.send_at_cmd(cmd).split('\r\n')
        r = list(filter(None, r))
        print("response={}".format(r))
        return r

    def blink(self, rgb, n):
        for i in range(n):
            pycom.rgbled(rgb)
            utime.sleep(0.25)
            pycom.rgbled(BLACK)
            utime.sleep(0.1)