READOUT: acquire images from the detectors

This page is part of the ING document INS-DAS-24: client-server interface for control of cameras

Purpose: perform one readout, capture the pixels and sort them by region.

Actors: udas_run client; udas_camera server; camera.

Outline: the client invokes the READOUT action. The server orders the camera to read out once. As the pixels arrive from the camera, the server captures and stores them, demultiplexing the pixel-stream during the readout to save processing time.

Normal course of events:

Client invokes the READOUT action on the server with no arguments.
Server orders camera to read out once.
As camera delivers pixels to the DAS computer, server reads them into memory and sorts them into contiguous regions of the focal plane.
Camera indicates that the readout is complete.
Server stores the sorted pixels for later use in other actions.
Server passes the sorted pixels to the raw-image display (c.f. DISPLAY action).
Server returns good status to client.

Variations:

Client invokes READOUT several times for one run. Server and camera do the same steps for each invocation. Server stores the pixels of successive readouts separately; the readouts do not overwrite each other and are not combined by the READOUT action.
The READOUT action is aborted by the ABORT or RESET actions (q.v.). Server returns status UDAS__ABORTED or UDAS__RESET respectively for these two cases.
Readout on the camera fails. Server writes an error message directly to the log and sends one of these stati to client:

camera rejected the command: UDAS__CAMCMDFAIL;
camera did not reply: UDAS__CAMLINKDOWN;
camera sent the wrong number of pixels: UDAS__ROFAIL.