Acquisition

Pymepix software can run in python environment imported as a module, or it can be started as a standalone server with REST-API. In latter case the image data could be retrieved through ZeroMQ channel. In following, the operation within python as an imported module is described.

Acquisition can be started and stopped by:

import time
from pymepix import Pymepix

#Connect
timepix = Pymepix(('192.168.1.10',50000))

#Start acquisition
timepix.start()

#Wait
time.sleep(1.0)

#Stop acquisition
timepix.stop()

Pymepix provides data as a tuple given by (MessageType,data). These are explained in Data Formats. Retrieving the data can be done in to ways: Polling or Callback

Polling

Polling is where pymepix will place anything retrieved from Timepix into a ring polling buffer. This is the default mode but to reenable it you can use:

>>> timepix.enablePolling(maxlen=1000)

where maxlen describes the maximum number of elements in the buffer before older values are overwritten.

The user can retrieve this data by using:

>>> timepix.poll()
(MessageType.RawData,(array[98732405897234589802345,dtype=uint8],12348798))

If there is nothing in the polling buffer then a PollBufferEmpty exception is raised The poll buffer is limited in size but can be extended by doing:

>>> timepix.pollBufferLength = 5000

This will clear all objects using the polling buffer.

Callback

The callback method allows the user to deal with the data immediately when it is recieved. Setting this will clear the polling buffer of any contents.

To set a callback, first you need a function, for example:

def my_callback(data_type,data):
    print('My callback is running!!!!')

The format of the function must accept two parameters, MessageType and an extra data parameter. These are explained in Data Formats. Now to make pymepix use it simply do:

>>> timepix.dataCallback = my_callback

Now when acquisition is started:

>>> timepix.start()

The output seen is:

.. code-block:: sh

My callback is running!!!! My callback is running!!!! My callback is running!!!! My callback is running!!!! My callback is running!!!!

Pipelines

Pymepix uses pipelines objects in order to process data. Each pipeline is set for each timepix device so each timepix can have a different data pipeline. You can configure them to postprocess or output data in certain ways. For example the PixelPipeline object will read from a UDP packet stream and decode the stream into pixel x, pixel y, time of arrival and time over threshold arrays. All data is progated forward through the pipeline so both UDP packets and decoded pixels are output.

To use the (default) PixelPipeline pipeline on the first connected timepix device you can do:

from pymepix.processing import PixelPipeline,CentroidPipeline

timepix[0].setupAcquisition(PixelPipeline)

If you need centroid you instead can do:

>>> timepix[0].setupAcquisition(CentroidPipeline)

Configuring the pipelines can be done using the acquisition property for the timepix device, for example to enable TOFs you can do:

>>> timepix[0].acquisition.enableEvents = True

A list of pipelines and setting can be found in acquisition()