Sutter Instrument Lambda 721, Operation Manual

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LAMBDA 721 OPERATION MANUAL – REV. 1.10C (20210517)
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4. EXTERNAL CONTROL OPERATIONS
Controlling the Lambda 721 externally via computer is accomplished by sending commands
over the USB interface between the computer and the relevant connector on the rear panel of
the Lambda 721 controller.
4.1 USB Interface
The USB device driver for Windows is downloadable from Sutter Instrument’s web site
(
www.sutter.com ). The Lambda 721 requires USB CDM (Combined Driver Model) Version
2.10.00 or higher. The CDM device driver for the Lambda 721 consists of two device drivers:
1) USB device driver, and 2) VCP (Virtual COM Port) device driver. Install the USB device
driver first, followed by the VCP device driver. The VCP device driver provides a serial RS-
232 I/O interface between a Windows application and the Lambda 721. Although the VCP
device driver is optional, its installation is recommended even if it is not going to be used.
Once installed, the VCP can be enabled or disabled.
The CDM device driver package provides two I/O methodologies over which communications
with the Lambda 721 can be conducted: 1). USB Direct, or 2). Serial RS-232 asynchronous
via the VCP device driver. The first method requires that the VCP device driver be disabled
(or not installed). The second method requires that the VCP be installed and enabled.
4.1.1 Virtual COM Port (VCP) Serial Port Settings
The following table lists the required RS-232 serial settings for the COM port (COM3,
COM5, etc.) generated by the installation of the VCP device driver.
Table 4-1. USB-VCP interface serial port settings.
Property Setting
Data (“Baud”) Rate (bits per second (bps))
(Configurable with rear-panel DIP Switch 5.) 9600*, 57600
Data Bits 8
Stop Bits 1
Parity None
Flow Control None
* Factory default setting.
The settings shown in the above table can be set in the device driver’s properties (via the
Device Manager if in Windows) and/or programmatically in your application.
4.2 Handshaking
Command sequences do not have terminators. If a command sequence just sent to the
controller is determined to be valid, the entire sequence is immediately echoed back to the
computer. All commands return an ASCII CR (Carriage Return; 13 decimal, 0D hexadecimal)
to indicate that the task associated with the command has completed. When the Lambda 721
completes the task associated with a command, it sends an ASCII CR back to the host
computer indicating that it is ready to receive a new command. If a command returns data,
the last byte returned is the task-completed indicator.