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Package for the COVMATIC Opentrons stations

Project description


This software is part of the Covmatic project.
Visit the website for more documentation and information.

:warning: This package is meant to be directly used only by an informed developer audience
Non-devs can more easily access the protocols implemented in this package via the Covmatic LocalWebServer GUI

Table of Contents


You can install the Covmatic Stations package via pip:

<python> -m pip install covmatic-stations

Where <python> should be changed for the Python instance you wish to install the LocalWebServer onto. We will be following this convention for all the next instructions.

Robot network configuration

See the config folder for robot network configuration protocols.


In the protocols directory you can find usage examples.

First, you have to import the station you want to use. In this example (protocols/, we will use the Station A class for the Technogenetics kit that uses custom 4x6 COPAN tube racks.

from covmatic_stations.a.technogenetics import StationATechnogenetics24

Then, you have to instantiate your own station. All classes come with a full set of default parameters, that you can change to suit your needs. E.g. let's assume you want to change the number of samples to 96.

station = StationATechnogenetics24(num_samples=96)

You can also specify your language: 'ENG' (default) or 'ITA'. This choice will affect the messages that the internal protocol server sends to the LocalWebServer. E.g.

station = StationATechnogenetics24(

You also have to define the metadata (at least the API level) as usual

metadata = {'apiLevel': '2.3'}

Finally, the definition of the run function becomes trivial

def run(ctx):

Extend stations

If you want to customize your station further than what changing parameters allows, you can create your own station class. First identify the base stations that you want to customize (e.g. StationBTechnogenetics).

You want to create a new class that extends that base class. The method body implements the core of the protocol instructions. Labware and instrument initialization is done before the body. Cleanup is done after.

To change the protocol procedure, override body.

If you want not to load a labware piece (or instrument), identify the corresponding loader method: it should be tagged by a @labware_loader (or @instrument_loader) decorator.

:warning: The method may be implemented by a parent class of the class you are looking at. If you don't find the method in the class you are extending, look in the parent classes.

If you want to load a new labware piece (or instrument), define a corresponding loader method: it should be decorated by a @labware_loader (or @instrument_loader) decorator. The decorators take two arguments

  • index: labware and instruments are loaded in the order defined by these indices (first all the labware, then all the instruments)
  • name: the name of the labware or instrument (for debug purposes)

An example of protocol file made by extending a station class could be

import logging
from covmatic_stations.b.technogenetics import StationBTechnogenetics

class CustomStation(StationBTechnogenetics)
    # override loader: tempdeck will not be loaded
    def load_tempdeck(self):
    # load a custom labware piece
    @labware_loader(10, "_custom_labware")
        self._custom_labware = self._ctx.load_labware(...)
    # override body: redefine the procedure
    def body(self)

# debug level brings up more log messages, try this when extending a new class
metadata = {'apiLevel': '2.3'}
station = CustomStation(num_samples=96)

def run(ctx):

:warning: If you are using the LocalWebServer GUI to upload the protocol file store this custom file in a different path than the one used for the automatically generated protocol

To upload this custom file using the LocalWebServer GUI:

  • Save the automatically generated protocol to a file
  • Copy the custom file to overwrite the automatically generated protocol
  • Upload the file (press the upload button)
  • Verify that the uploaded file is the correct one
    • Read the confirmation message: you should read that the expecte file has been uploaded

If the robot's Jupyter server is on, you can directly overwrite the protocol file on the robot via the Jupyter interface.


You can adjust the logging level of your station (e.g. to INFO) like so

import logging

By default, the level is set to DEBUG.

Copan 48 Rack correction

The station A protocols use a custom tube rack. The rack definition is generated by the corresponding class. Some fine redefinition may be needed. You can adjust the definition with a JSON file. All values in the JSON file are considered multipliers. E.g.

  "stagger": 1.27,
  "distance_vert": 0.98

This file specifies a stagger value 27% bigger than the theoretical value and a distance_vert value 2% smaller than the theoretical value.

If the default value is a tuple, use a list of multipliers. E.g.

  "global_dimensions": [1, 1.2, 0.9]

To override the default adjustments, you can set the environment variable OT_COPAN_48_CORRECT to the file path of your custom JSON.

Magnet Settings

Magnet settings are read from a JSON file in the package. To override the file path, you can set the environment variable OT_MAGNET_JSON to your custom path (a path on the OT's Raspberry). If the file was /home/altern_magnet.json, you would have to write

export OT_MAGNET_JSON=/home/altern_magnet.json

To delete the variable you can run


The JSON file should be an array of objects, each of which has the fields serial, station and height. E.g.

	"serial": "X",
	"station": "B1",
	"height": 6.20
	"serial": "Y",
	"station": "B2",
	"height": 6.20

To inspect a field of a magnet, use the following pattern magnets.<field>.by_<key>["keyvalue"]. E.g. to get the height of the magnet whose serial is X you would write

from covmatic_stations.b import magnets
h = magnets.height.by_serial["X"]


The package comes with some unit tests. If you want to run them then checkout the code, move to the code folder, install the package with: py install and then run the tests with: pytest

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