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Python driver for Honeywell Midas gas dectectors.

Project description


Python driver for Honeywell Midas gas detectors.


pip install midas

If you don’t like pip, you can also install from source:

git clone
cd midas
python install

This depends on pymodbus, which is not compatible with Python 3.


Command Line

To test your connection and stream real-time data, use the command-line interface. You can read the state with

$ midas
  "alarm": "none",
  "concentration": 0.0,
  "connected": true,
  "fault": {
    "status": "No fault"
  "flow": 495,
  "high-alarm threshold": 2.0,
  "ip": "",
  "life": 537.0,
  "low-alarm threshold": 1.0,
  "state": "Alarm or fault simulation",
  "temperature": 27,
  "units": "ppm"

or stream a table of data with the --stream flag. See midas --help for more.


For more complex behavior, you can write a python script to interface with other sensors and actuators.

from midas import GasDetector
gas_detector = GasDetector(ip_address='')

If the detector is operating at that IP address, this should return an output a dictionary of the form:

  'alarm': 'none',             # Can be 'none', 'low', or 'high'
  'concentration': 0.0,        # Current gas concentration reading
  'connected': True,           # Monitors heartbeat for connection
  'fault': {                   # Fault data, when applicable
    'code': 'F39',
    'condition': 'User has generated a simulated fault.',
    'description': 'Simulated fault',
    'recovery': 'Reset simulated fault.',
    'status': 'Instrument fault'
  'flow': 514,                 # Flow rate, in cc / minute
  'high-alarm threshold': 2.0, # Threshold concentration for high alarm trigger
  'ip': '',       # IP address of connection, can be used to link to Honeywell's own web interface
  'life': 538.95,              # Days until cartridge replacement required
  'low-alarm threshold': 1.0,  # Threshold concentration for low alarm trigger
  'state': 'Monitoring',       # Can be any option in `gas_detector.monitoring_status_options`
  'temperature': 26,           # Detector temperature, in celsius
  'units': 'ppm'               # Units for concentration values


The above example works for small numbers of gas detectors. At larger scales, the time spent waiting for detector responses is prohibitive. Asynchronous programming allows us to send out all of our requests in parallel, and then handle responses as they trickle in. For more information, read through krondo’s twisted introduction.

from midas import GasDetector
from twisted.internet import reactor, task

# As an example, assume we have six detectors in 192.168.1.[192-197].
gas_detectors = [GasDetector('192.168.1.{}'.format(i)) for i in range(192, 198)]

def on_response(response):
    """This function gets run whenever a device responds."""

def loop():
    """This function will be called in an infinite loop by twisted."""
    for detector in gas_detectors:

loop = task.LoopingCall(loop)

This looks more complex, but the advantages are well worth it at scale. Essentially, sleeping is replaced by scheduling functions with twisted. This allows your code to do other things while waiting for responses, letting you scale to thousands of devices.

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