LoRa-P2P

A Python interface for using LoRa Wio-E5 Development Kits for reliable Peer to Peer communication.

Dependencies

This package only uses the pyserial library. It can be installed here: The official PySerial docs

How to use

This section goes over the steps necessary to use the package and shows an example usage.

Preparation

After installing the pyserial library you need to find out what the port name is of the port that your LoRa node(s) is/are connected to. You can do this as follows:

import serial.tools.list_ports

ports = serial.tools.list_ports.comports()
for port in ports:
    print(f"{port.device}: {port.description}")

Now that you know the port, you can start sending messages.

If you do not have the LoRa kit connected to your PC at the moment, you can still execute example code by leaving the port parameter blank. This creates a mock instance of the LoRa module controller that will simulate the behaviour of a controller that is connected to real hardware.

Example

# ====== On a first device ======
def node1_response_to_message(message: bytes) -> bytes:
    if message == b"Hello?":
        return b"Hello!"
    else:
        return b"What??"

node1 = LoRaNode(port="COM4") # This is the port that you explored earlier
reliable_node1 = ReliableCommunicatingNode(node1, node1_response_to_message) # Pass the callback that formulates responses

# ====== On a second device ======
node2 = LoRaNode(port="COM5") # This is the port that you explored earlier
reliable_node2 = ReliableCommunicatingNode(node2) # For this example we keep the default handler

message = b"Hello?"
try:
    answer = reliable_node1.send_reliably_wait_for_answer(message, max_retries=1, retransmission_timeout=0.5)
    print(answer)
except TimeoutError:
    print("The message did not get a reply in the specified amout of tries")
# The reply should be b"Hello!" 

What this builds upon

This is all built upon the P2P functionality of the TEST mode in Wio-E5 Development Kits. These development kits can either listen or send. If they send, they stop listening for received packages until listening is explicitly enabled again. More information about these modules in TEST mode can be found in the official documentation for Wio-E5 Development Kits

A Normal setup for enabling listening and sending is given here:

Sending

> AT //checking the connection
+AT: OK 

>AT+MODE=TEST //enabling test mode
+MODE: TEST

>AT+TEST=TXLRPKT, "01234556789ABCDEF" //sending a hexadecimal packet
+TEST: TXLRPKT "001234556789ABCDEF"
+TEST: TX DONE

Receiving

> AT //checking the connection
+AT: OK 

>AT+MODE=TEST //enabling test mode
+MODE: TEST

>AT+TEST=RXLRPKT //enabling listening
+TEST: RXLRPKT

//when message received
+TEST: LEN:9, RSSI:-26, SNR:13
+TEST: RX "001234556789ABCDEF"

Class structure

class dependencies:

(format: <some_class> -> <classes_it_uses_to_work>)

ReliableCommunicatingNode -> LoRaNode
LoRaNode -> LoRaKitController, EitherSendOrListenNodeInterface
LoRaKitController -> ThreadedSerialReader, ReceivedDataMessageHandler

explanation:

• ReliableCommunicatingNode: uses a LoRaNode to send and receive messages, but on top of that, uses acknowledgements and retransmissions after a set timeout.
• LoraNode: is an implementation of EitherSendOrListenNodeInterface. Uses a LoRaKitController instance to initialise the LoRa module connected via a serial port and to send commands through the serial port to the LoRa device.
• LoRaKitController: has high level commands such as check_connection() and enable_listening(). It uses write_with_confirm to write a command over the serial connection and also check the response. It also uses a class ThreadedSerialReader to monitor the serial port for incoming messages. When a message comes in, it uses a ReceivedDataMessageParser to parse the lines as a ReceivedMessage
• ThreadedSerialReader: A class that monitors the serial port using a separate thread. It checks periodically after a certain timeout if there is a serial incoming message to be read. When some input is received, the thread handles it using the given callback given from higher up.