SKA PST LMC Architecture

SKA PST.LMC implements a single TANGO device, BEAM, that is deployed in a single TANGO Device server.

Full PST control and monitoring is accessed via the BEAM device. Following the SKA TANGO device naming convention, access to the Low PST Beam 1 would use the TANGO FQDN of low-pst/beam/01.

The BEAM device extends from the SKA TANGO base CSP Subelement Obs Device (ska_csp_lmc_base.CspSubElementObsDevice) which in turn extends from the Obs Device (ska_tango_base.obs.ObsDevice) and Base Device (ska_tango_base.base.SKABaseDevice).

BEAM

This logical device implements the single point of contact for monitor and control between PST and external systems, such as CSP.LMC or an engineering interface. It manages all of the other PST components, except for SEND (in AA0.5, components managed by LMC include SMRB, RECV, DSP.DISK, and STAT).

Component Managers

Within the BEAM device there are component managers that manage the RECV, SMRB, DSP, and STAT components.

The following UML diagram shows the internal software architecture of the BEAM and component managers.

@startuml LMC Class Diagram

class PstBeam <<tango>>
class PstBeamComponentManager

class PstRecvComponentManager
class PstRecvProcessApi

class PstSmrbComponentManager
class PstSmrbProcessApi

class PstDspComponentManager

class PstDspDiskComponentManager
class PstDspDiskProcessApi

class PstDspFlowThroughComponentManager
class PstDspFlowThroughProcessApi

class PstStatComponentManager
class PstStatProcessApi

PstBeam *-- PstBeamComponentManager
PstBeamComponentManager *-- PstRecvComponentManager
PstBeamComponentManager *-- PstSmrbComponentManager
PstBeamComponentManager *-- PstStatComponentManager
PstBeamComponentManager *-- PstDspComponentManager

PstRecvComponentManager *-- PstRecvProcessApi
PstSmrbComponentManager *-- PstSmrbProcessApi
PstStatComponentManager *-- PstStatProcessApi
PstDspDiskComponentManager *-- PstDspDiskProcessApi
PstDspFlowThroughComponentManager *-- PstDspFlowThroughProcessApi

PstDspComponentManager *-- PstDspDiskComponentManager
PstDspComponentManager *-- PstDspFlowThroughComponentManager

@enduml — Class diagram showing the BEAM TANGO device and the component managers

SMRB

This component manager controls and monitors the SMRB process that manages the ring buffers in shared memory.

RECV

This component manager controls and monitors the RECV process that is responsible for capturing UDP packet streams from the Correlator Beam Former and writing the data to ring buffers in shared memory.

DSP

This component manager controls and monitors the appropriate digital signal processing component within the PST component. During a configure scan request the DSP component manager will decide what specific DSP component to use. Each component has their own component manager, as seen in the above UML diagram.

Each DSP component reads incoming data from the ring buffer in shared memory and processes it according to the configured mode of operation. New modes of operation will be made available with each array assembly:

AA0.5 voltage recorder (DSP.DISK) writes raw data from the beam former to files on disk
AA1.0 search mode - including the flow through mode (DSP.FT) which does channel and polarisation selection and requantisation the complex voltage data.
AA2.0 timing mode

STAT

This component manager controls and monitors the STAT process that reads incoming data from the ring buffer in shared memory, computes various statistical quantities that can be used to evaluate data quality, and publishes these quantities to configured subscribers (currently an HDF5 file writer and TANGO-based monitor).