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operations.rst.txt 9.54 KiB
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Configuration file
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==================
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The configuration of the OhmPi file `config.py` allows to configure the OhmPi.
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A default version of `config.py` is provided in the repository.
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This file should be edited to customize the configuration following the user's needs and preferences.
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The configuration includes setting the logging level desired for the different loggers and handlers, setting the mqtt broker(s) used for logging and control of the OhmPi and defining the options used for MQTT communication (i.e. username, password, security options...)
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One should make sure to understand the parameters before altering them. It is also recommended to keep a copy of the default configuration.
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Interfaces and applications
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===========================
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Different interfaces can be used to interact with the OhmPi.
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Available interfaces are:
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- `Web interface`_ (=HTTP interface): run in bash: `bash run_http_interface.sh`
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- Python API: import the OhmPi class from Python script: `from ohmpi import OhmPi` (see `Python interface`_)
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- MQTT: IoT messaging through a broker (see `MQTT interface`_)
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Web interface
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.............
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This is a user friendly graphical interface for new users as well as running quick and easy acquisitions.
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The Raspberry Pi of the OhmPi is used as a Wi-Fi Access Point (AP) and runs
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a small webserver to serve the 'index.html' interface. Using a laptop or
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a mobile phone connected to the Wi-Fi of the Raspberry Pi, one can see this
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interface, upload sequences, change parameters, run a sequence and download data.
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To configure the Raspberry Pi to act as an access point and run
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the webserver automatically on start, see instructions on `raspap.com <https://raspap.com/>`_ and in 'runOnStart.sh'.
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Once configured, the webserver should start by itself on start and once
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connected to the Pi, the user can go to `10.3.141.1:8080 <http://10.3.141.1:8080>`_
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to access the interface.
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.. figure:: ../../img/http-interface-pseudo-section.png
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    Web interface with its interactive pseudo-section.
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.. figure:: ../../img/http-interface-evolution.png
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     Evolution of quadrupole apparent resistivity with time.
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.. figure:: ../../img/http-interface-rs.png
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     Contact resistance check.
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Python interface
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................
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This interface offers a more direct access to the software components especially well suited for testing or automation on the Raspberry Pi.
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By importing the `OhmPi` class from the ohmpi.py, one can control the OhmPi using interactive IPython.
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Typically, it involves using the terminal or an Python IDE such as Thonny on the Raspberry Pi. One can also connect using
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ssh and run the Python interface (see PuTTY on Windows or ssh command on macOS/Linux).
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To access the Python API, make sure the file ohmpi.py is in the same
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directory as where you run the commands/script. The file ohmpi.py can
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be found on the OhmPi gitlab repository. We recommend downloading the
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entire repository as ohmpi.py import other .py files and default configuration files (.json and .py). .. code-block:: python :caption: Example of using the Python API to control OhmPi import os import numpy as np import time os.chdir("/home/pi/OhmPi") from ohmpi import OhmPi ### Define object from class OhmPi k = OhmPi() # this loads default parameters from the disk ### Default parameters can also be edited manually k.settings['injection_duration'] = 0.5 # injection time in seconds k.settings['nb_stack'] = 1 # one stack is two half-cycles k.settings['nbr_meas'] = 1 # number of time the sequence is repeated ### Update settings if needed k.update_settings({"injection_duration":0.2}) ### Set or load sequence k.sequence = np.array([[1,2,3,4]]) # set numpy array of shape (n,4) # k.set_sequence('1 2 3 4\n2 3 4 5') # call function set_sequence and pass a string # k.load_sequence('ABMN.txt') # load sequence from a local file ### Run contact resistance check k.rs_check() ### Run sequence (synchronously - it will wait that all # sequence is measured before returning the prompt k.run_sequence() # k.run_sequence_async() # sequence is run in a separate thread and the prompt returns immediately # time.sleep(2) # k.interrupt() # kill the asynchron sequence ### Run multiple sequences at given time interval k.settings['nb_meas'] = 3 # run sequence three times k.settings['sequence_delay'] = 100 # every 100 s k.run_multiple_sequences() # asynchron # k.interrupt() # kill the asynchron sequence ### Single measurement can also be taken with k.switch_mux_on([1, 4, 2, 3]) k.run_measurement() # use default acquisition parameters k.switch_mux_off([1, 4, 2, 3]) # don't forget this! risk of short-circuit ### Custom or adaptative argument, see help(k.run_measurement) k.run_measurement(nb_stack=4, # do 4 stacks (8 half-cycles) injection_duration=2, # inject for 2 seconds autogain=True) # adapt gain of ADS to get good resolution MQTT interface .............. This is an interface designed for an advanced remote usage of the OhmPi such as remote automation, data consumption by multiple processes and interaction with other sensors in the scope of a monitoring. It is based on the MQTT protocol, designed for the Internet of Things (IoT), to interact with the OhmPi. This option allows interacting remotely with a single OhmPi, a network of OhmPis, as well as auxiliary instruments and sensors. The communication is based on a publish/subscribe approach and involves a MQTT broker. An example of MQTT broker that can be used is `Mosquitto <https://mosquitto.org/>`_. Depending on the monitoring needs, an MQTT broker can be set up locally on the Raspberry Pi, on a local network or any remote server reachable through the net. A local Mosquitto broker can be set up and enabled to run as a service on the OhmPi using the bash script install_local_mqtt_broker.sh. MQTT messages include logging messages from the OhmPi and commands sent to the OhmPi. These messages can be examined easily using a third party software such as `MQTT Explorer <http://mqtt-explorer.com/>`_. Commands sent on the broker are received by the ohmpi.py script that runs on the OhmPi (make sure ohmpi.py starts on reboot) and further processed. MQTT commands are sent in JSON format following the Python API with kwargs as illustrated below:
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.. code-block:: json :caption: Updating acquisition settings. { "cmd_id": "3fzxv121UITwGjWYgcz4xw", "cmd": "update_settings", Depending on the experiment needs, MQTT brokers can be set up locally on the Raspberry Pi or on a local or remote server. "kwargs": { "config": { "nb_meas": 2, "nb_electrodes": 10, "nb_stack": 2, "injection_duration": 2, "sequence_delay": 100 } } } .. code-block:: json :caption: Check contact resistances { "cmd_id": "3fzxv121UITwGjWYgcz4xw", "cmd": "rs_check", } .. code-block:: json :caption: Running a sequence. { "cmd_id": "3fzxv121UITwGjWYgcz4Yw", "cmd": "run_sequence", } .. code-block:: json :caption: Running same sequence multiple times (nb_meas). { "cmd_id": "3fzxv121UITwGjWYgcz4Yw", "cmd": "run_multiple_sequences", } .. code-block:: json :caption: Interrupt current acquisition. { "cmd_id": "3fzxv121UITwGjWYgcz4xw", "cmd": "interrupt", } Custom processing of messages and tailor-made dashboards for monitoring experiments may be designed using a browser-based flow editor such as `Node-red <http://mqtt-explorer.com/>`_. This may help designing complex IoT experiments and monitoring systems in which OhmPi is a component. Examples incorporating execution commands and data outputs from OhmPi can be found in the OhmPi examples. Once Node-RED is installed on the OhmPi, these examples can be accessed separately by running a command in the console such as : .. code-block:: console node-red basic_ohmpi_flows_node-red.json These examples may require installing some additional node packages in order to work properly. This can be done in the `Palette Manager <https://nodered.org/docs/user-guide/editor/palette/manager>`_ within Node-RED. .. figure:: ../../img/node-red_flow.png Example flow in node-red to interact with an OhmPi. .. figure:: ../../img/node-red_interface_control.png Example of a dashboard UI created with node-red to interact with an OhmPi - control tab.
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.. figure:: ../../img/node-red_interface_data.png Example of a dashboard UI created with node-red to interact with an OhmPi - data visualization tab. For more documentation dedicated to node-red, please refer to the Node-red `cookbooks <https://cookbook.nodered.org/>`_. Loggers ------- Loggers have been introduced in this release. They use the excellent logging python package. Specific handlers have been implemented for running with ohmpi.py (one for logging to an mqtt broker (see `MQTT interface`_ for more details) and one for creating zipped rotated logs on disk). Two loggers have been defined. The first one is dedicated to log operations execution. It is named exec_logger. The second one, named data_logger, is dedicated to log data. A third one is planned to log the state of health (SOH) of the system in a future version. By default, logs are written to the console (print-like), stored locally in files (a zip is created after some time i.e. every day and/or when the size of the log exceeds a maximum size) and sent to an MQTT broker. Different logging levels may be defined for the different logs and handlers in the `Configuration file`_. Advanced users may write new handlers and edit the `setup_loggers.py` file to customize the logging mechanisms to their needs.