Difference between revisions of "Gpibgrok"
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* [http://www.datasheetarchive.com/dl/Datasheets-112/DSAP0051077.pdf Fairchild 96LS488] | * [http://www.datasheetarchive.com/dl/Datasheets-112/DSAP0051077.pdf Fairchild 96LS488] | ||
* [http://www.datasheetarchive.com/dl/Datasheets-24/DSA-476449.pdf NEC uPD7210C/D] | * [http://www.datasheetarchive.com/dl/Datasheets-24/DSA-476449.pdf NEC uPD7210C/D] | ||
* [http://www.datasheetarchive.com/dl/Datasheets-313/195317.pdf National NAT9914] | * [http://www.datasheetarchive.com/dl/Datasheets-313/195317.pdf National Instruments NAT9914] ([http://sine.ni.com/nips/cds/view/p/lang/de/nid/11153 NI page], [http://www.ni.com/pdf/products/us/4gpib705.pdf NI datasheet]) | ||
(pretty much all of them are no longer available) | (pretty much all of them are no longer available) | ||
Revision as of 03:29, 28 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
- Right-angle PCB mounted male
- Norcomp 112-024-113R001: about $5.5
- TE Connectivity 5552741-1: about $7.2
GPIB protocol chips
- Philips/NXP HEF4738
- Fairchild 96LS488
- NEC uPD7210C/D
- National Instruments NAT9914 (NI page, NI datasheet)
(pretty much all of them are no longer available)
GPIB transceiver chips
- National DS75160A
- SN75160B: Octal General-Purpose Interface Bus Transceiver (datasheet). Mouser: €1.55
- SN75161B: Octal General-Purpose Interface Bus Transceiver (datasheet). Mouser: €1.45
- SN75162B: Octal General-Purpose Interface Bus Transceiver (datasheet). Mouser: €2.03
Resources
- Massimiliano Gentile's thesis on writing a USBTMC driver for the AVR32 architecture.
- Hack a Day: GPIB connectivity twofer (covers Galvant GPIBUSB and Sven Pauli's RS232-GPIB interface)
- GPIB connector pinout