wlmodem 1.1.1

Python library for Water Linked underwater modems

Python library for Water Linked underwater modems

Python library for communicating with Water Linked underwater modems.

The library exposes the functionality of the modem: setting configuration, getting diagnostic, sending and receiving packets.

Resources

• Water Linked web site
• Modem documentation
• Modem protocol specification
• Repository

Requirements

• Python 2.7 or Python 3.6
• pyserial
• crcmod

Supported modems

• Water Linked Modem-M64

Setup

$ python3 -m pip install --user wlmodem
or
(venv)$ python3 -m pip install wlmodem

Quick start

Connecting to a modem and configuring the mode and channel:

$ python3

>>>  from wlmodem import WlModem
>>>  modem = WlModem("/dev/ttyUSB0")
>>>  modem.connect()
True
>>>  modem.cmd_configure("a", 4)
True
>>>  modem.cmd_queue_packet(b"HelloSea")
True

Usage

The WlModem class provides an easy interface to configure, send and receive data with a Water Linked modem. A pair of modems must be configured on the same channel and with different roles to establish communication between them.

A WlModem object is initialized with the serial device name:

from wlmodem import WlModem
modem = WlModem("/dev/ttyUSB0")

Call connect() to establish communication with the device

if not modem.connect():
    print("Failed connecting to modem")
    sys.exit(1)

Once connected we set the same channel and different roles on the pair of modems:

# On modem 1:
success = modem.cmd_configure("a", 4)
# On modem 2:
success = modem.cmd_configure("b", 4)

If the tip of the modems are close to each other (<5cm) the modems will now link up. The link status can be seen on the LEDs or by getting the diagnostic data.

if modem.cmd_get_diagnostic().get("link_up"):
    print("Link is up")

Once we have connected we can use cmd_queue_packet function to queue data for transmission.

success = modem.cmd_queue_packet(b"HelloSea")

In order to get data which one modem has received from the other modem use the get_data_packet function. This function will by default wait timeout seconds until a data packet is received before returning. If timeout is 0 it will immediately return with a packet (if available) or None if no packet has been received.

pkt = modem.get_data_packet(timeout=0)
if pkt:
    print("Got data:", pkt)

Simulator

A WlModemSimulator class can be used to simulate communication with a modem without a physical modem. Once instantiated the object will behave similarly to a Water Linked Modem-M64. Data packets that are queued using the simulator object is returned after a timeout.

>>> from wlmodem import WlModemSimulator
>>> modem = WlModemSimulator()
>>> modem.connect()
True
>>> modem.cmd_queue_packet(b"HelloSim")
True
>>> modem.get_data_packet()
b'HelloSim'

Example

A larger example is available in example/example.py.

Development

The code in this repository is unit tested with pytest. tox is used to automate testing on multiple Python versions.

Run unit-tests with:

pip install tox
tox