liteserver 2.0.0

Lightweight control system for scientific instruments. Like EPICS but much simpler

liteserv

Very Lightweight Data Object Server. It hosts Lite Data Objects (LDO, analog of process variables in EPICS) and provides info/set/get/read/subscribe remote access to them using UDP protocol. Data encoding is implemented using MessagePack specification, which makes it very fast and efficient.

Data logging and retrieving

Data objects can be logged and retrieved using an apstrim package (https://pypi.org/project/apstrim).

Bridged usage

To monitor and control liteserv-served devices from an existing architecture one can use or build a simple bridge:

A bridge for RHIC ADO Control architecture is liteServerMan.py

liteServerMan.py -HmyHost myADO.

An ADO manager liteServerMan.py connects to a liteServer, running on myHost and creates the myADO.

• All input LDOs are translated to myADO input parameters.
• All output parameters of the myADO are translated to LDOs.

For EPICS Control architecture

The bridge liteServer-EPICS can be developed using a python-based implementation of IOC, for example: caproto

Features

• Simplicity. The network protocol is UDP, error correction of late/missing/mangled data is implemented. The serialization protocol is MessagePack: binary, easier than RPC, provides all JSON features. All this makes it possible to implement liteServer on a CPU-less FPGA.
• Low latency, connection-less.
• Supported requests:
  • info(), returns dictionary with information on requested LDOs and parameters
  • get(), returns dictionary of values of requested LDOs and parameters
  • read(), returns dictionary of changed readable (non-constant) parameters of requested LDOs
  • set(), set values or attributes of requested LDO parameters
  • subscribe(callback), subscribe to a set of the objects, if any object of the requested LDOs have been changed, the server will publish the changed objects to client and the callback function on the client will be invoked.
• Multidimensional data (numpy arrays) are supported.
• Access control info (username, program name) supplied in every request
• Name service
  • file-based
  • network-based using a dedicated liteServer (not commissioned yet)
• Basic spreadsheet-based GUI: pypet
• Architectures. All programs are 100% python. Tested on Linux and Windows.
• Supported applications:
  • Image analysis
  • Data Logger

Key Components

• liteServer: Module for building liteServer applications.
• liteAccess: Module for for accessing the Process Variables from a liteServer.
• liteCNS.py: Name service module, it provides file-based (liteCNS_resolv.py) or network-based name service (liteCNSserver.py).

Supportted devices

Server implementations for various devices are located in .device sub-package. A device server can be started using following command:

python3 -m liteserv.device.<deviceName> <Arguments>

• device.litePeakSimulator: Waveform simulator with multiple peaks and
• device.liteScaler: test implementation of the liteServer , supporting 1000 of up/down counters as well as multi-dimensional arrays. a background noise. pan, zoom and tilt control.
• device.senstation: Server for various devices, connected to Raspberry Pi GPIOs: 1-wire temperature sensor, Pulse Counter, Fire alarm and Spark detector, Buzzer, RGB LED indicator, OmegaBus serial sensors. Various I2C devices: ADC: ADS1115, Magnetometers: MMC5983MA, HMC5883, QMC5983. NUCLEO-STM33 mixed signal MCU boards, connected to Raspberry Pi over USB.
• device.liteGQ: Geiger Counter and a gyro sensor GMC-500 from GQ Electronics.
• device.liteWLM: Server for Wavelength Meter WS6-600 from HighFinesse.
• device.liteLabjack: LabJack U3 analog and digital IO module.
• device.liteUSBCam: Server for USB cameras.
• device.liteUvcCam: Server for USB cameras using UVC library, allows for
• device.liteVGM: (Obsolete) Server for multiple gaussmeters from AlphaLab Inc.

Installation

Python3 should be 3.6 or higher.

python3 -m pip install liteserver

Additional libraries may be required for specific devices.

Examples

Most convenient way to test base class functionality is by using ipython3,

Start a server liteScaler on a local host:

python3 -m liteserver.device.liteScaler -ilo -s2
ipython3

from liteserver import liteAccess as LA 
from pprint import pprint

Host = 'localhost'
LAserver = Host+':server'
LAdev1   = Host+':dev1'
LAdev2   = Host+':dev2'

#``````````````````Programmatic way, using Access`````````````````````````````
list(LA.Access.info((Host+':*','*')))# list of all devices on the Host
LA.Access.info((LAserver,'*'))
LA.Access.get((LAserver,'*'))
LA.Access.set((LAdev1,'frequency',[2.0]))
LA.Access.subscribe(LA.testCallback,(LAdev1,'cycle'))
LA.Access.unsubscribe()
#,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,	
#``````````````````Object-oriented way````````````````````````````````````````
# Advantage: The previuosly created PVs are reused.
allServerParameters = LA.PVs((LAserver,'*'))
pprint(allServerParameters.info())
pprint(allServerParameters.get())# get all parameters from device LAserver
# get all readable parameters from device Scaler1:server, which have been 
# modified since the last read:
pprint(allServerParameters.read())

allDev1Parameters = LA.PVs((LAdev1,'*'))
print(allDev1Parameter.info())

server_performance = LA.PVs((LAserver,'perf'))
pprint(server_performance.info())
pprint(server_performance.get())
# simplified get: returns (value,timestamp) of a parameter 'perf' 
pprint(server_performance.value)

server_multiple_parameters = LA.PVs((LAserver,('perf','run')))
pprint(server_multiple_parameters.info())
pprint(server_multiple_parameters.get())

server_multiple_devPars = LA.PVs((LAdev1,('time','frequency')),(LAserver,('statistics','perf')))
pprint(server_multiple_devPars.get())

# setting
dev1_frequency = LA.PVs((LAdev1,'frequency'))
dev1_frequency.set([1.5])
dev1_frequency.value
dev1_multiple_parameters = LA.PVs([LAdev1,('frequency','coordinate')])
dev1_multiple_parameters.set([8.,[3.,4.]])

# subscribing
ldo = LA.PVs([LAdev1,'cycle'])
ldo.subscribe()# it will print image data periodically
ldo.unsubscribe()# cancel the subscruption

# test for timeout, should timeout in 10s:
#,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
#``````````````````Observations```````````````````````````````````````````````
    # Measured transaction time is 1.8ms for:
LA.PVs([[['Scaler1','dev1'],['frequency','command']]]).get()
    # Measured transaction time is 6.4ms per 61 KBytes for:
LA.PVs([[['Scaler1','dev1'],'*']]).read() 
#``````````````````Tips```````````````````````````````````````````````````````
# To enable debugging: LA.PVs.Dbg = True
# To enable transaction timing: LA.Channel.Perf = True