PEM200 User Manual
32
7
Communication Protocol
The Hinds PEM200 controller drives a single PEM at a user selectable amplitude of
modulation. The PEM200 communicates over USB as a simple SerialCOM device. The
communication protocol is a derivative of the SCPI protocol common to many
instruments. In this document, the basic SCPI protocol is outlined. From there, the
specific connection requirements are outlined. Finally, the full command list and
explanation for each command is given.
Port Settings
PEM-200 connects to the computer as a USB serial COM port. The connection baud
rate is 250,000 bytes per second. As this is a USB serial port, the software defined
baud rate can be set anywhere from 9,600 to 250,000 and the PEM-200 should still
communicate.
Standard Commands for Programmable Instruments (SCPI) protocol
SCPI protocol is a standard syntax for controlling programmable devices. The protocol
outlines a common syntax, command structure and data format. Commands are text
strings sent to the device as either set operations (eg “:MODulator:VOLTage 0.25”) or
get operations (“:MODulator:VOLTage?”). Set operations are often followed by a text
string containing numerical or string data (eg. “:MODulator:VOLTage 0.1”). Get
operations end with a ‘?’ and return data. Similar commands are grouped with similar
leading strings in a tree structure.
Commands can be abbreviated by sending only the capitalized portion of the command
text. Such as “:MODulator:VOLTage 0.1” can be abbreviated as “:MOD:VOLT 0.1”.
Commands are terminated with a new line character (also known as line feed, ‘\n’,
ASCII DEC 10, ASCII HEX A) or a semicolon (‘;’). Carriage returns are ignored as many
terminal applications send a full new line and carriage return by default. All commands
are case sensitive.
