Difference between revisions of "Gpibgrok"

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=== GPIB connectors ===
=== GPIB connectors ===


* Right-angle PCB mounted male
* Right-angle, PCB mounted, male:
** Norcomp 112-024-113R001: [http://octopart.com/partsearch#search/requestData&q=Norcomp+112-024-113R001 about $5.5]
** Norcomp 112-024-113R001: [http://octopart.com/partsearch#search/requestData&q=Norcomp+112-024-113R001 about $5.5]; [http://de.mouser.com/ProductDetail/NorComp/112-024-113R001/?qs=IGgAdOvCTsSdej4q2f%2fo5Q%3d%3d Mouser] (2.80€, but not available ATM)
** TE Connectivity 5552741-1: [http://octopart.com/partsearch#search/requestData&q=TE%20Connectivity%205552741-1 about $7.2]
** TE Connectivity 5552741-1: [http://octopart.com/partsearch#search/requestData&q=TE%20Connectivity%205552741-1 about $7.2]; [http://de.mouser.com/ProductDetail/TE-Connectivity-AMP/5552741-1/?qs=ZDXmSm13592KDB5YbnOqGQEXH8vBFTre66B%2ffSd9ajU%3d Mouser] (5.87€, but not available, and minimum quantity required)
* Straight (no right-angle), PCB mounted, male:
** [http://www.te.com/catalog/pn/en/552283-1 TE Connectivity / AMP 552283-1]: [http://de.mouser.com/ProductDetail/TE-Connectivity-AMP/552283-1/?qs=L%252bK8JgcrFouKshZpXbu%2foxXjsnB6QVdhWc5JSE3CA%2fU%3d Mouser] (4.08€)
* Straight (no right-angle), solder-cup, male:
** [http://www.amphenolcanada.com/ProductSearch/drawings/AC/5720240.pdf Amphenol 57-20240]: [http://de.mouser.com/ProductDetail/Amphenol-Commercial-Products/57-20240/?qs=9QC6KritiMlxI%2fbOR6fN8o%2fx9VH%2fvGRssdGjBll89tQ%3d Mouser] (4.93€) TODO: Typo on page/datasheet, or is this really female?


=== GPIB protocol chips ===
=== GPIB protocol chips ===

Revision as of 11:26, 29 May 2012

This page documents some ideas and information for a GPIB-USBTMC hardware interface.

Motivation

There are many ways to communicate with devices that have a GPIB port, and sigrok aims to support as many of them as possible (see IEEE-488). However in this day and age the only reasonable interface for this would have to use a USB device port, since USB host ports are so ubiquitous. The USB standards include a device class specifically made for test and measurement, called the USBTMC class.

Yet most of the GPIB-USB interfaces available don't use this device class; they typically use either a proprietary protocol or serial emulation. There is only one GPIB-USBTMC interface that we know of: the TEK-USB-444 from Tektronix, and it's ridiculously overpriced at around $740.

We think we can make a GPIB-USBTMC interface that is:

  • 100% free and open source, hardware and firmware/software
  • 100% standards-compliant
  • Considerably cheaper than anything else out there (less than $50)

In addition, since we'd be making essentially a "server-side" i.e. USB device-side implementation of the USBTMC protocol, this code would be reusable in projects such as Das Oszi.

Hardware design

  • Using an ARM Cortex-M3 microcontroller would get us:
    • Built-in USB
    • Plenty of horsepower to handle the throughput a GPIB device will reasonably need
    • Many different implementations to choose from, and many inexpensive development boards
    • Can start with an existing development board + GPIB connector
  • Voltage levels on GPIB pins is "negative logic with standard TTL levels": true <= 0.8V, false >= 2.0V. (to be verified)

Software

Due to the long history of the IEEE-488 and SCPI standards, there are many devices out there supporting some earlier version of the protocol, and these will typically support commands that are vendor-specific, and syntax that is not compliant IEEE-488. Therefore supporting various device-specific or vendor-specific "quirks" will likely be a big part of real-world use-cases.

Components

GPIB connectors

GPIB protocol chips

(pretty much all of them are no longer available)

GPIB transceiver chips

Resources