seedlink_raw_plugin

Seedlink plugin for custom data streaming to SeisComP

This plugin can be included in the SeisComP Seedlink implementation and allows to stream custom data to SeisComP. This RAW plugin, running within the seedlink server, connects to the provided raw_server.py, which has to run on the device that provides the data.

The raw_server.py provides the API to stream your data without worring about the protocol details. If you cannot use the raw_server in your device, you can create your own implementation and use raw_server.py as a reference.

How it works

The RAW plugin and server implement a barebone minimalistic protocol for data exchange. When the seedlink plugin connects to a raw server, it selects a channel (or more). A channel is just a numeric id used to distinguish multiple streams available in a raw_server. The server then specifies the data settings for every channel before streaming it. These settings may be:

• int8, int16, int32, float32, float64
• little-endian, big-endian
• sample rate (max 1MHz)

The data packets, once received by the seedlink plugin, are eventually converted to miniseeds and passed to seedlink server, which make them available to any application connecting to it e.g. SeisComP.

The raw_server.py runs as a separate process and inter process communication is used to pass the data between your code and the server. The server itself uses asyncio to achive high performance. All these details are hiddend behind a nice API layer. To use raw_server.py as a module you can have a look at the __main__ function as a reference, which contains a test program that can be used to send sample data for testing. However the general idea is the following:

import sys
import datetime
import numpy as np

import raw_server as rs

#
# Set the preferred log levels for the api and the server processes
# The spawned server(s) will log to the file raw_servers.log
#
logging.getLogger("raw_api").setLevel(logging.INFO)
logging.getLogger("raw_server").setLevel(logging.INFO)

#
# Channel defines the properties of the data we want to stream
# In this exaple we stream 2 sensors, each one with 3 components, that we
# intend to map in seiscomp to a single station with 2 location codes:

# Station 1 (3 components)
c1 = rs.Channel(id=1, samprate=200, endianness=sys.byteorder, samptype="int32")
c2 = rs.Channel(id=2, samprate=200, endianness=sys.byteorder, samptype="int32")
c3 = rs.Channel(id=3, samprate=200, endianness=sys.byteorder, samptype="int32")

# Station 2 (3 components)
c4 = rs.Channel(id=4, samprate=100, endianness=sys.byteorder, samptype="int16")
c5 = rs.Channel(id=5, samprate=100, endianness=sys.byteorder, samptype="int16")
c6 = rs.Channel(id=6, samprate=100, endianness=sys.byteorder, samptype="int16")

#
# create a streaming server that will run as a separate process and wait for
# connection on `port=65535
#
streamer = rs.Streamer(channels=[c1,c2,c3,c4,c5,c6], host="127.0.0.1", port=65535)
streamer.start()

#
# Read data from hardware and pass it to the streamer that makes them available
# to whoever connects to it adn request the registered channels
#
while True:
  #
  # Here put your device logic: once you got the device data (samples and
  # sample time) pass it to the streamer via `streamer.feed_data()` method
  #
  sta1_samptime, sta1_comp1_samples, sta1_comp2_samples, sta1_comp3_samples = device_driver_station1.get_data()
  sta2_samptime, sta2_comp1_samples, sta2_comp2_samples, sta2_comp3_samples = device_driver_station2.get_data()

  # channel_id: what channel the data belongs to
  # samptime: start timestamp of the samples (type datetime.datetime)
  # samples: array like (numpy array, list) containing the data samples, which
  #           will be converted by the api to the Channel samptype and endianness
  #           before streaming it
  #
  streamer.feed_data( channel_id=1, sta1_samptime, sta1_comp1_samples )
  streamer.feed_data( channel_id=2, sta1_samptime, sta1_comp2_samples )
  streamer.feed_data( channel_id=3, sta1_samptime, sta1_comp3_samples )

  streamer.feed_data( channel_id=4, sta2_samptime, sta2_comp1_samples )
  streamer.feed_data( channel_id=5, sta2_samptime, sta2_comp2_samples )
  streamer.feed_data( channel_id=6, sta2_samptime, sta2_comp3_samples )

Installation

Simply drop the code in the seiscomp/src/base/seedlink/ folder and edit seiscomp/src/base/seedlink/plugins/CMakeLists.txt to compile the raw_plugin too during the compilation/installation process.

Configuration

To make this plugin work within SeisComP you need to provides the seedlink bindings for your station. In the bindings you need to select the raw plugin and configure it with the address of the raw server, then select the channel ids you want to request and how to map these channel ids to the location and channel codes of the station.

You can use raw_server.py for testing the bindings: when running python raw_server.py it will stream sample data in various formats (see the __main__ function for details). Configure the bindings to connect to localhost and run python raw_server.py to see if all works fine, at least with the sample data.