# areaDetector Plugin NDPluginStdArrays

## September 19, 2008

## Mark Rivers

## University of Chicago

## Contents

- Overview
- Configuration
- Screen shots
- IDL image display client
- Future plans

## Overview

This plugin is the tool for converting the NDArray data produced by asynNDArrayDriver drivers into a form that can be accessed by EPICS.

NDPluginStdArrays inherits from NDPluginDriver. NDPluginStdArrays converts the NDArray data from a callback into the 1-dimensional arrays supported by the standard asyn array interfaces, i.e. asyn[Int8, Int16, Int32, Float32, Float64]Array. These interfaces are supported by the EPICS waveform record using standard asyn device support. Because this plugin inherits from NDPluginDriver it also provides additional information on the array data (e.g. number of dimensions and dimension data) that are made available as EPICS PVs so that clients can correctly interpret the array data. The NDPluginStdArrays public interface is defined in NDPluginStdArrays.h as follows:

    class NDPluginStdArrays : public NDPluginDriver {
    public:
        NDPluginStdArrays(const char *portName, int queueSize, int blockingCallbacks,
                          const char *NDArrayPort, int NDArrayAddr,
                          size_t maxMemory);

        /* These methods override the virtual methods in the base class */
        void processCallbacks(NDArray *pArray);
        virtual asynStatus readInt8Array(asynUser *pasynUser, epicsInt8 *value,
                                            size_t nElements, size_t *nIn);
        virtual asynStatus readInt16Array(asynUser *pasynUser, epicsInt16 *value,
                                            size_t nElements, size_t *nIn);
        virtual asynStatus readInt32Array(asynUser *pasynUser, epicsInt32 *value,
                                            size_t nElements, size_t *nIn);
        virtual asynStatus readFloat32Array(asynUser *pasynUser, epicsFloat32 *value,
                                            size_t nElements, size_t *nIn);
        virtual asynStatus readFloat64Array(asynUser *pasynUser, epicsFloat64 *value,
                                            size_t nElements, size_t *nIn);
        asynStatus drvUserCreate(asynUser *pasynUser, const char *drvInfo,
                                            const char **pptypeName, size_t *psize);
    ...
    }

NDPluginStdArrays defines the following parameters. It also implements all of the standard plugin parameters from NDPluginDriver . The EPICS database NDStdArrays.template provides access to these parameters, listed in the following table.

Parameter Definitions in NDPluginStdArrays.h and EPICS Record Definitions in NDStdArrays.template
Enum name | asyn interface | Access | Description | drvUser string | EPICS record name | EPICS record type
--- | --- | --- | --- | --- | --- | ---
NDPluginStdArraysData | asyn[Int8, Int16, Int32, Float32, Float64]Array | r/o | Array data as a 1-D array, possibly converted in data type from that in the NDArray object to the specific asyn interface. | STD_ARRAY_DATA | $(P)$(R)ArrayData | waveform

If the array data contains more than 16,000 bytes then in order for EPICS clients to receive this data they must be built with EPICS R3.14 (not R3.13), and the environment variable EPICS_CA_MAX_ARRAY_BYTES on both the EPICS IOC computer and EPICS client computer must be set to a value at least as large as the array size in bytes.

## Configuration

The NDPluginStdArrays plugin is created with the following command, either from C/C++ or from the EPICS IOC shell.

    drvNDStdArraysConfigure(const char *portName, int queueSize, int blockingCallbacks,
                            const char *NDArrayPort, int NDArrayAddr, size_t maxMemory)

Argument | Description
--- | ---
`portName` | The name of the asyn port for this plugin.
`queueSize` | The maximum number of NDArray objects that can be queued for processing. Passed to the NDPluginDriver base class constructor.
`blockingCallbacks` | Flag controlling whether callbacks block. Passed to the NDPluginDriver base class constructor.
`NDArrayPort` | The name of the asyn port of the driver that will provide the NDArray data. Passed to the NDPluginDriver base class constructor.
`NDArrayAddr` | The asyn addr of the asyn port of the driver that will provide the NDArray data. Passed to the NDPluginDriver base class constructor.
`maxMemory` | Maximum number of bytes of memory to be allocated from the NDArrayPool. Passed to the constructor for the NDPluginDriver base class. The NDStdArrays plugin allocates 2 NDArray objects, so this should be at least twice the size of the largest NDArray to be used.

## Screen shots

The following is the MEDM screen that provides access to the parameters in NDPluginDriver.h and NDPluginStdArrays.h through records in NDPluginBase.template and NDStdArrays.template. This is the MEDM screen that is normally used to control the display of images via EPICS channel access.

### NDStdArrays.adl

## IDL Image Display Client

There is an IDL procedure called epics_ad_display that can be used to display 2-dimensional array data that the NDStdArrays plugin sends to EPICS. This IDL client is available as source code (which requires an IDL license), and also as a pre-built IDL .sav file that can be run for free under the IDL Virtual Machine. This IDL program can run on any machine that IDL runs on, and that has the ezcaIDL shareable library built for it. This includes Windows, Linux, Solaris, and Mac. `epics_ad_display` is included in the CARS IDL imaging software.

The control window for `epics_ad_display` is shown below. It has a field to input the base name of the EPICS PVs with the image data. It also has fields to enable/display the IDL display update, to change the display mode, to autoscale the intensity, and to invert the image in the Y direction. If autoscale is set to No then manual scaling can be entered in the Min and Max fields. The number of frames per second actually being displayed by IDL is shown. There is a status window that shows whether the EPICS PVs are connected and the time the last was array received, updated once per second.

### Main window for IDL epics_ad_display

`epics_ad_display` can use the simple IDL routine `tv` to display the images. This is the fastest mode, and results in a non-scalable unadorned window.

### IDL epics_ad_display using the IDL `tv` routine.

`epics_ad_display` can also use the routine image_display.pro to display the images. This routine displays row and column profiles as the cursor is moved. It allows changing the color lookup tables, and zooming in (right mouse click) and out (left mouse click). The following is an example of `image_display` displaying an image from the simulation detector.

### epics_ad_display using the image_display routine

## Future plans

Stephen Mudie at the Australian Synchrotron has written a very nice IDL client to display the EPICS images from the Flea Firewire cameras. This client should be converted to display the data from this areaDetector plugin.