Add a Serial Instrument

This section contains information that applies to Windows and Linux, not Windows on ARM.

A serial instrument is any instrument connected to an RS-232 COM port on the local PC. (To add instruments connected to an RS-232 COM port on a LAN gateway or on another PC that is acting as a remote I/O server, see Add a Remote Serial Instrument.)

The VISA identifier ASRL<n> identifies the serial interface on which the instrument will reside. Typically, you'll have one interface for each serial port (COM port) available on your PC. For example, ASRL3 typically identifies the port known to Windows as COM3.

Notes:

  • Serial instruments cannot be auto-discovered by the Keysight Instrument Discovery Service. You must manually add all serial instruments. See Instrument Discovery and Identification on Specific Interface Types for more information.

  • The instrument's settings must match the serial instrument's settings. Making changes to the interface properties does not change the settings on the serial instrument.

To add a serial instrument:

  1. Click , select Serial instrument on ASRLn from the context list.

  2. Modify the interface properties (described in detail below) as needed.

  3. Click OK to add this interface to your configuration.

Connection Addresses

VISA Interface ID

A name used by VISA and Keysight software to uniquely identify this interface. For a serial interface, the VISA interface ID is of the form ASRLn, where n is an integer typically corresponding to the serial port number to which the instrument is connected: for example, ASRL3 for serial port COM3.

SICL Interface ID

The unique ID that SICL programs use to identify this interface. The default SICL interface ID is COMn, where n is an integer. If you are not using the default SICL interface ID, enter a unique string of alphanumeric characters (it can also include the _ and - characters). The SICL interface ID can be a maximum of 31 characters long and must start with a letter. Take note of this value and the logical unit number in order to address the interface in your SICL applications.

Logical Unit

An integer that can be used in place of the SICL interface ID in Keysight VEE and SICL applications. The logical unit is not used by VISA.

Configure Serial Properties

Baud Rate

The speed of data transmission and reception on the RS-232 serial interface. The baud rate you select depends on the instrument you connect to the serial port. Check the documentation for your peripheral device to set this value.

Data Size

The number of data bits in a character frame in RS-232 serial data transmission. The data size you select depends on the peripheral device (instrument) you connect to the serial port. Check the documentation for your instrument to set this value. Available choices are 5, 6, 7, and 8.

Flow Control

The protocol used to pace data transmission over the RS-232 serial connection. The flow control you select depends on the peripheral device you connect to the serial port. Check the documentation for your peripheral device to set this value. Available choices are NONE, XON/XOFF, RTS/CTS, and DTR/DSR.

VISA supports the combinations "RTS/CTS AND XON/XOFF" and ""DTR/DSR AND XON/XOFF" for the serial interface's flow control property, but there is not a way to set those states in Keysight software. Both hardware and software flow control can be enabled simultaneously in code. Refer to the Keysight VISA Help page on ASRL Flow Control Combinations for additional information.

Stop Bits

The number of bits used to indicate the end of a character frame in RS-232 serial data transmission. The number of stop bits you select depends on the peripheral device you connect to the serial port. Check the documentation for your peripheral device to set this value. Available choices are 1 and 2.

Parity

Parity is used by the RS-232 serial hardware to verify data transmission. The parity value you select depends on the peripheral device you connect to the serial port. Check the documentation for your peripheral device to set this value. Available choices are NONE, ODD, EVEN, SPACE, and MARK.

SRQ Line

The SRQ line is the modem status line on the serial interface that is monitored for Service ReQuests (SRQs). Available choices are RI, CTS, DSR, and DCD.

Some instruments have the capability of requesting service from the controller. On the IEEE-488 GPIB bus, this is called an SRQ (Service ReQuest). An SRQ notifies the controller that the instrument needs service.

The SRQ Line value is used to select one of the four RS-232 status lines for SRQ events. When this line toggles, any handlers installed for this interface with the ionsrq SICL function will be called. The default SRQ Line is the Ring Indicator (RI) line.

Auto-identify This Instrument

When this check box is selected, an *IDN? query is sent to the instrument periodically. When this check box is cleared, this instrument is excluded from periodic identifications.

When auto-identification is enabled for an instrument, the Discovery Service sends an identification query (*IDN?) to determine the instrument's identity when it is added. You may want to disable auto-identification on certain instruments, including:

  • Register-based instruments. Register-based VXI instruments do not respond to the *IDN? query. Sending *IDN? to a register-based instrument creates a failure.
  • Older instruments. Some older instruments may not handle the *IDN? string well.
  • Shared instruments. For LAN instruments and instruments on remote interfaces, sending the *IDN? string could interrupt a running program and interfere with measurements.

Verify Connection

The VISA address (connection string) for a serial instrument combines the VISA interface ID and the letters INSTR; for example, ASRL1::INSTR. Once you have configured the connection information, you will see the generated VISA address in the field to the right of the button labeled Test This VISA Address.

When you click the Test This VISA Address button, the software will attempt to connect to the instrument at that address. The state of the connection is then displayed below the VISA address, and if the connection succeeds, the manufacturer, model, and serial number are displayed below that. (If the instrument does not return a valid serial number, or if the serial number is 0, a placeholder in the form *VISAAddress is shown instead.)

The state of the connection is typically Verified or Failed. If the connection failed, details of the failure may also be displayed.

Saving the Configuration

The OK button is enabled if you have made changes to the information in this view. When you have finished entering the information, click OK to save the configuration or Cancel to revert to default values.

 

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