py-opc-ng 0.0.1

Python library to operate Alphasense OPC particle counters

py-opc-ng

A small python library to operate Alphasense OPC devices.

Supports most modern OPC devices: OPC-N2, OPC-N3, OPC-R1 and OPC-R2.

Installation

$ pip install py-opc-ng

Dependencies

The devices work with SPI interface. You can either connect them directly to a SPI bus using py-spidev (e.g. with the GPIO pins of a RaspberryPi) or use a SPI to USB device, like the one Alphasense provides, using the pyusbiss library.

Usage

With a direct SPI connection:

from time import sleep
import spidev
import opcng as opc

spi = spidev.SpiDev()
spi.open(0, 0)
spi.mode = 1
spi.max_speed_hz = 500000
spi.lsbfirst = False

dev = opc.detect(spi)

print(f'device information: {dev.info()}')
print(f'serial: {dev.serial()})
print(f'firmware version: {dev.serial()}')

# power on fan and laser
dev.on()

for i in range(10):
    # query particle mass readings
    sleep(1)
    print(dev.pm())

# power off fan and laser
dev.off()

or with a SPI to USB bridge:

from time import sleep
from usbiss.spi import SPI
import opcng as opc

spi = SPI('/dev/ttyACM0')
spi.mode = 1
spi.max_speed_hz = 500000
spi.lsbfirst = False

dev = opc.detect(spi)

print(f'device information: {dev.info()}')
print(f'serial: {dev.serial()}')
print(f'firmware version: {dev.serial()}')

# power on fan and laser
dev.on()

for i in range(10):
    # query particle mass readings
    sleep(1)
    print(dev.pm())

# power off fan and laser
dev.off()

A note about the name

When this project was started the most popular library to operate Alphasense OPC devices was py-opc. At the time it only supported OPC-N2 and had a lot of code very specific to that device generation.

Adding support for next generation (hence the -ng) devices there seemed to require quite some effort. We wanted to abstract common characteristics of the different devices in a single interface right from the start. We also didn't want to support all the quirks they had for N2 different firmware versions as we were already moving away from N2 devices.

So we opted to start a completely new project. It's not a fork and doesn't share any code with py-opc.

License

This module is licensed under the GNU Lesser General Public License Version 3. Full text can be found in the LICENSE file.

Acknowledgement

This package was developed within the Cagliari2020 project with the support of Istituto Nazionale di Fisica Nucleare (INFN)