Control with RS-232 / serial port

Networked VGA Grid presents an RS-232 / serial port control interface (via USB) for integration with existing control room and board room equipment. This section covers the following topics:

Connect and configure the RS-232 cable
Control the Networked VGA Grid with RS-232
RS-232 / Serial port command examples

Connect and configure the RS-232 cable

To connect your control equipment to the Networked VGA Grid you will need a standard RS-232 null-modem cable and a USB to RS-232 serial adapter cable. Adapter cables are not included with the Networked VGA Grid. Only certain adapter chipsets are supported, Epiphan recommends this adapter cable from Startech.

To connect the serial port cable:

Attach the null modem cable to the control interface.
Connect the USB to RS-232 serial adapter to the null-modem cable.
Connect the USB to RS-232 serial adapter to one of the system’s USB ports.

The only configuration available for the serial port is flow control. Flow control changes the rate of data transfer over the cable. Some communication settings are static and cannot be changed. The static settings are:

Baud rate set at 19200
Parity set to none
Stop bits set to one

To configure serial port flow control:

Select the Serial Port link in the Configuration menu; the serial port configuration page opens.
Select Hardware, Software, or None from the drop-down menu. Refer to the table below for a description of the options.

Serial Port Flow Control Options

Label	Description / Options
Hardware	A hardware handshake mechanism is used for flow control. This is also called RTS / CTS flow control. Select this when your control terminal requires it (see control terminal manual).
Software	A software handshake that uses XON/XOFF characters to control the flow of data. Select this when your control terminal requires it (see control terminal manual).
None	No flow control is used. Only select this if your control terminal requires it (see control terminal manual).

Click Apply.

Control the Networked VGA Grid with RS-232

You can use the null-modem cable and your control terminal software to issue commands to the Networked VGA Grid such as when to start or stop recording, or to retrieve or set the value for various settings.

Each command sent to the Networked VGA Grid via RS 232 must be terminated with a line feed (LF) character (ASCII code 10). Your software may need to be configured to add the line feed to each command.

Some commands require a channel or recorder name as an argument. In those commands, the channel or recorder name is separated from the command name by a period, as shown in the table. The channel name value can be either the name or the index of the recorder or channel. Use of the index is recommended.

A channel's index is found by looking at the Channels list in the Admin panel. In the screen capture below, the channel with index 1 is currently recording (it's index number is red). To address this channel via RS-232 commands, use the index 1.

For commands requiring a recorder index, determine your recorder's index by combining the recorder's number with the prefix m. In the example below, the second recorder's index is 2. To access this recorder via RS-232 commands, use the index m2.

The table describes the RS-232 commands supported by the Networked VGA Grid.

Supported RS-232 Commands

Command Name	Description
Recording Commands
START.<channel> START.<recorder>	Starts recording for the provided channel or recorder. This can alternatively be accomplished with the following set commands: SET.<channel>.rec_enabled=on SAVECFG If the channel is already recording, the current recording is continued.
START	Starts recording for all channels and recorders. There is no RS-232 command to restart recording. If recording is already active when the start command is issued, the recording continues.
STOP.<channel> START.<recorder>	Stops recording for the provided channel or recorder. This can alternatively be accomplished with the following set commands: SET.<channel>.rec_enabled="" SAVECFG
STOP	Stops recording for all channels and recorders.
SNAPSHOT.<channel>	Takes a snapshot image of the current channel (supported only if the channel is configured to use the Motion JPEG codec). Snapshots are saved with recording files on the system.
SNAPSHOT	Takes a snapshot image of all channels (supported only for channels configured to use the Motion JPEG codec). Snapshots are saved with recording files on the system.
Configuration Commands (see Configuration keys for third party APIs for available keys)
GET.<channel>.<key> GET.<recorder>.<key>	Gets the saved value of a given parameter for the specified channel or recorder.
SET.<channel>.<key> SET.<recorder>.<key>	Sets the value of a given parameter for the specified channel or recorder. The value is not saved until the SAVECFG command is sent.
SAVECFG	Saves the parameters modified by the SET command.
Status Commands
STATUS.<channel> STATUS.<recorder>	Reports the recording status of the specified channel or recorder. Status is one of: RUNNING STOPPED UNINITIALIZED
STATUS	Reports the recording status of each channel and recorder. Status is one of: RUNNING STOPPED UNINITIALIZED
FREESPACE	Reports the free storage space, in bytes.
RECTIME.<channel> RECTIME.<recorder>	Reports the elapsed recording time for the current file on the specified channel or recorder.
RECTIME	Reports the elapsed recording time for the current file on each channel.

Additionally, the system automatically reports its status changes back along the RS-232 connection using the following automatic messages:

RS-232 Status Changed Messages

Command Name	Description
STATUS.<channel> <status>	Provides the status of the recording service for the channel's as one of: Running Stopped Uninitialized The Uninitialized status is sent when there is an internal error. Check the system for more details.

Command Name

Description

STATUS.<channel> <status>

Provides the status of the recording service for the channel's as one of:

Running
Stopped
Uninitialized

The Uninitialized status is sent when there is an internal error. Check the system for more details.

RS-232 / Serial port command examples

The following examples demonstrate how to use some of the RS-232 commands supported by the system. The list of supported SET and GET parameters are found in Configuration keys for third party APIs .

For values with spaces, enclose the value in quotation marks. For empty values, use empty quotation marks with nothing between.

You must always follow a "SET" command in RS-232 with the "SAVECFG" command. Otherwise the new configuration setting(s) will not take effect. See "SET" examples below.

1. To start recording on channel 2:

START.2

2. To stop recording on channel 2:

STOP.2

3. To start recording on all channels and recorders:

START

4. To get the value of the frame size (resolution) for channel 2:

GET.2.framesize

5. To set the frame size (resolution) on channel 2, enclose the parameter in quotes to preserve the spaces:

SET.2.framesize="640 x 480"
SAVECFG

6. To enable broadcasting audio on channel 2:

SET.2.audio=on
SAVECFG

7. To disable broadcasting audio on channel 2:

SET.2.audio=""
SAVECFG