SCPI-Lite

Light-weight SCPI library for easy scripting access to instruments

This library abstracts the underlying transport between computer and the instrument. Goal is to allow easy "scripting" withouth having to worry about the physical transport. And being able to talk to any device implementing SCPI (or "SCPI like") protocol, withouth having to have device / dialect specific driver.

Currently supported transports (backends) are:

• Serial
• TCP/IP
• Linux USBTMC (/dev/usbtmc*)
• USBTMC (direct USB access)

Requirements

Library has been written on Python 3.x. It uses following Python modules:

• serial (pySerial)
• usbtmc - needed for direct USB access (not needed if using Linux USBTMC)

Usage

This module provides SCPIDevice class that represents connection to instrument.

Device string parameter is used to automaticallyd determine underlying transport to use:

Transport	Example	Notes
USBTMC	USB::0x1ab1::0x0e11::INSTR	Connect to USBTMC device using usbtmc module
Linux USBTMC	/dev/usbtmc0	Connect to USBTMC device using Linux kernel module
TCP	192.168.42.42:5555	Connect to device using TCP/IP
Serial	/dev/ttyS0, /dev/ttyUSB0, or COM1: (Windows)	This is the default method if devices string doesnt match to any known format

Connection examples:

dev = scpi_lite.SCPIDevice('/dev/usbtmc0')

dev = scpi_lite.SCPIDevice('/dev/ttyUSB0', baudrate=115200, timeout=5)

dev = scpi_lite.SCPIDevice('192.168.42.42:5555', timeout=5)

Generic options for SCPIDevice class

Following options are supported by the SCPIDevice class currently:

Option	Description	Example
idn	Device supports *IDN? command (boolean) [Default: True]	idn=False
opc	Device supports *OPC? command (boolean) [Default: True]	opc=False
err	Device supports SYST:ERR? command (boolean) [Default: True]	err=False
command_terminator	Command terminator (allows overriding SCPI default in case of non-compliant device) [Default: \n]	command_terminator=''
encoding	Command (string) encoding [Default: utf-8]

Transport specific options for SCPIDevice class

There are transport specific options that can be passed throug as well:

Transport	Option	Description	Example
all	timeout	Timeout for waiting response from the instrument (in seconds) [Default: 5]	timeout=10
all	verbose	Enable verbose/debug output (boolean) [Default: False]	verbose=True
serial	terminator	Response terminator (allows working with devices no complying with SCPI spec) [Default: \n]	terminator=b'\n\r'
serial	baudrate	Baud rate (bps) [Default: 115200]	baudrate=9600
serial	bytesize	Byte size [Default: EIGHTBITS]	bytesize=serial.SEVENBITS
serial	parity	Parity [Default: PARITY_NONE]	parity=serial.PARITY_EVEN
serial	stopbits	Stop bits [Default: STOPBITS_ONE]	stopbits=serial.STOPBITS_TWO
serial	xonxoff	Use XON/XOFF flow-controll [Default: Flase]	xonxoff=True
serial	rtscts	Use RTS/CTS flow-control [Default: False]	rtscts=True
serial	dsrdtr	Use DSR/DTR flow-control [Default: False]	dsrdtr=True

Examples

import scpi_lite

print('scpi_lite version: ',scpi_lite.VERSION)


# connect to instrument

#dev = scpi_lite.SCPIDevice('USB::0x1ab1::0x0e11::INSTR')
#dev = scpi_lite.SCPIDevice('/dev/usbtmc0')
dev = scpi_lite.SCPIDevice('192.168.42.42:5555')

# enable debug output
dev.verbose=1

# display instrument model and firmware version
print('Instrument: %s v%s' % (dmm.model, dmm.firmware))

# send a 'query' to instrument
val = dev.query('SYST:VERS?')
print('response: ', val)

# if there was error running query error can be checked using last_error variable
print('result: ', psu.last_error)


# send a command to instrument
res = dev.command('SYST:REM')

# check if command was successfull
print('result', res)