epicsdisplay -- Display epics channels


epicsdisplay channel file


Monitors a set of EPICS channels in tabular and, optionally, chart recorder form. channelfile is the name of a file that describes the epics channels to monitor. The file consists of two types of text lines; comments and channel lines. Comment lines begin with the hash character lines begin with a channel name followed by whitespace, followed by an optional comment. If the optional comment contains the special word ââchartââ, the channel is added to the chart recorder.

Channels can also have alarms defined on them. An alarm is said to fire whenâ[m ever the channel value is outside of a ânominalâ window. Alarms are also defined using special keywords in the comment field of the channel. The keyâ[m word nominal indicates that the next word on the line defines the channelâs nominal window. The nominal window definition can be defined either symmetriâ[m cally or asymmetrically about a nominal value. The nominal window can also be defined in absolute terms or in terms of a percentage of nominal value. Describing nominal windows is most easily done via example.

nominal 35:3

Defines a symmetric nominal window about the nominal value 35. This nominal window is the range 32 through 38.

nominal 35:10%

Defines a nominal interval that is +/- 10% of 35... e.g. the interval 32.5 through 38.5

nominal 35+3-4

Defines a nominal window between 31 and 38. Similarly:

nominal 35+5%-10%

Defines the nominal interval 32.5 through 36.75. Note that for asymmetric intervals mixes of absolute and percentage tolerances are allowed. Furthermore, the - and + are interchangeable.

When a channel transitions to the alarmed state, actions defined on the comment line for the channel are taken. Actions are defined by the keyword alarmmactions followed by a comma separated list of actions. Supported actions are:


The alarm is added to a page that describes all the current alarms.


A beep is periodically emitted while the channel is in the alarmed state.


A popup window is displayed when the alarm is in the alarmed state.


The alarm is displayed with the specified colorspec colored background. colorspec is a color using any color specification that is recognized by Tcl. (.e.g. color=red is the same as color=#ff0000).


The display is divided into three sections. The top section is the channel table. The middle section the chart recorder section and the bottom section the chart control panel.

While it appears as if the table section has no controls, in reality it is possible to resize all of the columns of the table. Expanding the window width adds space to the right most, Comment column. All other columns may be expanded by dragging their borders with the mouse.

The chart recorder control panel allows the user to perform a few operations on the chart. The Clear button resets the time to 0 and clears the data accumulated so far.

The rightmost three controls manage the time scale of the chart widget. Changes to these widgets do nothing until the Set button is clicked. The widget states at that time determine the scale of the chart recorder. If the ââAuto Rangeââ checkbutton is set, the time scale will change dynamically to accomodate the full time range of values. If unchecked, the value in the entry widget labelled Range (min): determines the width in time of the chart. The chart is scrolled as needed (by 10% of the range) to keep the most recent data visible.