LoRa.ABP Downlink messages no receive

[constantinos]

I have implemented a LoRa nanogateway with LoPy connected to TTN.
I have also another LoPy (Node) transmitting data via this gateway.

Whenever I create a downlink message via TTN I can see it in nanogateway but the message is never arrived at LoPy Node.

[jcaron]

You are aware that downlink messages are send only as a reply to an uplink? So you need to send an uplink to receive a previously queued downlink.

Also, it would probably help if you shared your code.

[constantinos]

@jcaron I know that you must perform an uplink in order to have a downlink.

The strange thing is that the nanogateway makes the LoRa TX but nothing is received.

Nano Gateway code

""" LoPy Nano Gateway class """

from network import WLAN
from network import LoRa
from machine import Timer
from network import Server as tcpserver

import os
import binascii
import machine
import json
import time
import errno
import _thread
import socket


PROTOCOL_VERSION = const(2)

PUSH_DATA = const(0)
PUSH_ACK = const(1)
PULL_DATA = const(2)
PULL_ACK = const(4)
PULL_RESP = const(3)

TX_ERR_NONE = "NONE"
TX_ERR_TOO_LATE = "TOO_LATE"
TX_ERR_TOO_EARLY = "TOO_EARLY"
TX_ERR_COLLISION_PACKET = "COLLISION_PACKET"
TX_ERR_COLLISION_BEACON = "COLLISION_BEACON"
TX_ERR_TX_FREQ = "TX_FREQ"
TX_ERR_TX_POWER = "TX_POWER"
TX_ERR_GPS_UNLOCKED = "GPS_UNLOCKED"

STAT_PK = {"stat": {"time": "", "lati": 0,
                    "long": 0, "alti": 0,
                    "rxnb": 0, "rxok": 0,
                    "rxfw": 0, "ackr": 100.0,
                    "dwnb": 0, "txnb": 0}}

RX_PK = {"rxpk": [{"time": "", "tmst": 0,
                   "chan": 0, "rfch": 0,
                   "freq": 868.1, "stat": 1,
                   "modu": "LORA", "datr": "SF7BW125",
                   "codr": "4/5", "rssi": 0,
                   "lsnr": 0, "size": 0,
                   "data": ""}]}

TX_ACK_PK = {"txpk_ack":{"error":""}}


class NanoGateway:

    def __init__(self, id, frequency, datarate, ssid, password, server, port, ntp='pool.ntp.org', ntp_period=3600):
        self.id = id
        self.frequency = frequency
        self.datarate = datarate
        self.sf = self._dr_to_sf(datarate)
        self.ssid = ssid
        self.password = password
        self.server = server
        self.port = port
        self.ntp = ntp
        self.ntp_period = ntp_period

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

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

        self.udp_lock = _thread.allocate_lock()

        self.lora = None
        self.lora_sock = None

    def start(self):
        # Change WiFi to STA mode and connect
        print("Starting nanogateway")
        self.wlan = WLAN(mode=WLAN.STA)
        self._connect_to_wifi()

        # Get a time Sync
        self.rtc = machine.RTC()
        self.rtc.ntp_sync(self.ntp, update_period=self.ntp_period)

        # Get the server IP and create an UDP socket
        self.server_ip = socket.getaddrinfo(self.server, self.port)[0][-1]
        print("Gateway IP:",self.server_ip)
        self.sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
        self.sock.setsockopt(socket.SOL_SOCKET, socket.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
        _thread.start_new_thread(self._udp_thread, ())

        # Initialize LoRa in LORA mode
        self.lora = LoRa(mode=LoRa.LORA, frequency=self.frequency, bandwidth=LoRa.BW_125KHZ, sf=self.sf,
                         preamble=8, coding_rate=LoRa.CODING_4_5, tx_iq=True)
        # Create a raw LoRa socket
        self.lora_sock = socket.socket(socket.AF_LORA, socket.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)
        print("Started")
    def stop(self):
        # TODO: Check how to stop the NTP sync
        # TODO: Create a cancel method for the alarm
        # TODO: kill the UDP thread
        self.sock.close()

    def _connect_to_wifi(self):
        self.wlan.connect(self.ssid, auth=(None, self.password))
        while not self.wlan.isconnected():
            time.sleep(0.5)
        print("WiFi connected!")
        tserver=tcpserver()
        tserver.deinit()
        tserver.init(login=("nemet", "nemet.gr"), timeout=60)

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

    def _sf_to_dr(self, sf):
        return self.datarate

    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 json.dumps(STAT_PK)

    def _make_node_packet(self, rx_data, rx_time, tmst, sf, 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]["datr"] = self._sf_to_dr(sf)
        RX_PK["rxpk"][0]["rssi"] = rssi
        RX_PK["rxpk"][0]["lsnr"] = float(snr)
        RX_PK["rxpk"][0]["data"] = binascii.b2a_base64(rx_data)[:-1]
        RX_PK["rxpk"][0]["size"] = len(rx_data)
        return json.dumps(RX_PK)

    def _push_data(self, data):
        token = os.urandom(2)
        packet = bytes([PROTOCOL_VERSION]) + token + bytes([PUSH_DATA]) + binascii.unhexlify(self.id) + data
        with self.udp_lock:
            try:
                self.sock.sendto(packet, self.server_ip)
            except Exception:
                print("PUSH exception")

    def _pull_data(self):
        token = os.urandom(2)
        packet = bytes([PROTOCOL_VERSION]) + token + bytes([PULL_DATA]) + binascii.unhexlify(self.id)
        with self.udp_lock:
            try:
                self.sock.sendto(packet, self.server_ip)
            except Exception:
                print("PULL exception")

    def _ack_pull_rsp(self, token, error):
        TX_ACK_PK["txpk_ack"]["error"] = error
        resp = json.dumps(TX_ACK_PK)
        packet = bytes([PROTOCOL_VERSION]) + token + bytes([PULL_ACK]) + binascii.unhexlify(self.id) + resp
        with self.udp_lock:
            try:
                self.sock.sendto(packet, self.server_ip)
            except Exception:
                print("PULL RSP ACK exception")

    def _lora_cb(self, lora):
        events = lora.events()
        if events & LoRa.RX_PACKET_EVENT:
            self.rxnb += 1
            self.rxok += 1
            rx_data = self.lora_sock.recv(256)
            print("LoRa_RX:",rx_data)
            stats = lora.stats()
            self._push_data(self._make_node_packet(rx_data, self.rtc.now(), stats.rx_timestamp, stats.sfrx, stats.rssi, stats.snr))
            self.rxfw += 1
        if events & LoRa.TX_PACKET_EVENT:
            self.txnb += 1
            lora.init(mode=LoRa.LORA, frequency=self.frequency, bandwidth=LoRa.BW_125KHZ,
                      sf=self.sf, preamble=8, coding_rate=LoRa.CODING_4_5, tx_iq=True)

    def _send_down_link(self, data, tmst, datarate, frequency):
        self.lora.init(mode=LoRa.LORA, frequency=frequency, bandwidth=LoRa.BW_125KHZ,
                       sf=self._dr_to_sf(datarate), preamble=8, coding_rate=LoRa.CODING_4_5,
                       tx_iq=True)
        while time.ticks_us() < tmst:
            pass
        print("LoRa_TX",data)
        self.lora_sock.send(data)

    def _udp_thread(self):
        while True:
            try:
                data, src = self.sock.recvfrom(1024)
                
                _token = data[1:3]
                _type = data[3]
                if _type == PUSH_ACK:
                    print("Push ack")
                elif _type == PULL_ACK:
                    print("Pull ack")
                elif _type == PULL_RESP:
                    self.dwnb += 1
                    ack_error = TX_ERR_NONE
                    tx_pk = json.loads(data[4:])
                    tmst = tx_pk["txpk"]["tmst"]
                    t_us = tmst - time.ticks_us() - 5000
                    if t_us < 0:
                        t_us += 0xFFFFFFFF
                    if t_us < 20000000:
                        self.uplink_alarm = Timer.Alarm(handler=lambda x: self._send_down_link(binascii.a2b_base64(tx_pk["txpk"]["data"]),
                                                                                               tx_pk["txpk"]["tmst"] - 10, tx_pk["txpk"]["datr"],
                                                                                               int(tx_pk["txpk"]["freq"] * 1000000)), us=t_us)
                    else:
                        ack_error = TX_ERR_TOO_LATE
                        print("Downlink timestamp error!, t_us:", t_us)
                    self._ack_pull_rsp(_token, ack_error)
                    print("Pull rsp")
            except socket.timeout:
                print("Socket Timeout")
            except OSError as e:
                if e.errno == errno.EAGAIN:
                    #print("UDP recv errno.EAGAIN")
                    pass
                else:
                    print("UDP recv OSError Exception")
            except Exception:
                print("UDP recv Exception")
            # Wait before trying to receive again
            time.sleep(0.025)

Node code

from network import LoRa
import socket
import binascii
import struct
import time
import pycom


pycom.heartbeat(False)

# Initialize LoRa in LORAWAN mode.
lora = LoRa(mode=LoRa.LORAWAN)

# create an ABP authentication params
dev_addr = struct.unpack(">l", binascii.unhexlify('260110AD'.replace(' ','')))[0]
nwk_swkey = binascii.unhexlify('2F8184207979F18CE1F64B6B74B75A99'.replace(' ',''))
app_swkey = binascii.unhexlify('53A7AA9AFA94FEB1F859F76EF5E0BA4C'.replace(' ',''))

# join a network using ABP (Activation By Personalization)
lora.join(activation=LoRa.ABP, auth=(dev_addr, nwk_swkey, app_swkey))

# remove all the non-default channels
for i in range(3, 16):
    lora.remove_channel(i)

# set the 3 default channels to the same frequency
lora.add_channel(0, frequency=868100000, dr_min=0, dr_max=5)
lora.add_channel(1, frequency=868100000, dr_min=0, dr_max=5)
lora.add_channel(2, frequency=868100000, dr_min=0, dr_max=5)

# create a LoRa socket
s = socket.socket(socket.AF_LORA, socket.SOCK_RAW)

# set the LoRaWAN data rate
s.setsockopt(socket.SOL_LORA, socket.SO_DR, 5)

# make the socket blocking
s.setblocking(False)
i = 1
while True:
    pycom.rgbled(0x100000)
    print("sending:",i,i % 255,"msg:",struct.pack('LB',i,i % 255))
    s.send(struct.pack('LB',i,i % 255))
    time.sleep(1)
    pycom.rgbled(0x001000)
    for k in range(29):
        rx = s.recv(256)
        if rx:
            print("RX:",rx)
        time.sleep(1)
    i += 1