Data Acquisition: Communication Protocols Beyond Labview - GPIB, VISA, and SCPI, Study notes of Engineering

Download Data Acquisition: Communication Protocols Beyond Labview - GPIB, VISA, and SCPI and more Study notes Engineering in PDF only on Docsity! Data Acquisition Computer interfaces and Software beyond Labview Industry standards GPIB - General Purpose Interface Bus VISA - Virtual Instrument Standard Architecture SCPI - Standard Commands for Programmable Instruments How does the computer talk to the hardware? The term “driver” is broadly used and often refers to code that interacts directly with the hardware (called device drivers) or code that interacts with the high level software such as Labview (called an instrument driver or library). One problem with this scheme is that it is often unique to that hardware and often inflexible. GPIB - Bus management These are connected in parallel to all devices and are ACTIVE LO. ATN - separates commands (LO) from data (HI) IFC - asserted by controller to set system to a predetermined state. REN - asserted by controller to enable devices for control. EOI - means “End Or Identify” and often used for multi-line transfers. SRQ - some action by the controller is requested by a device. The response is serial or parallel poll GPIB - Handshake Handshake Lines - remember how RAM write work or how RS-232 serial works. In both cases there are control signals that determine timing of writing. •Listener indicates ready to LISTEN •Talker puts data on bus and indicates it is valid •Listener accepts data •Talker stops sending data (data not valid) •Listener ready for last bit. DAV NRFD NDAC GPIB - Commands The format of the command is standard but cryptic. It is almost register style commands. These are sent as a byte over the data lines when ATN is LO. Examples Take control 0000 1001 Listen Address 1011 xadd Unlisten 0011 1111 The difficulty with these commands are that from a programming point of view they are implemented in software in different manners by different vendors.