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

NOTE: This project is on hold currently, nobody is working on it.


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)


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.


GPIB connectors

GPIB protocol chips

(pretty much all of them are no longer available, or horribly expensive, or hard to get, or a combination thereof)

GPIB transceiver chips

Bill of materials

(work in progress)

Qty Device Footprint Value Refdes Digikey Mouser Comments
1 ST STM32F103C6T6A LQFP-48 ... ... 4.54€ ... ...
1 TI SN75160B ... ... ... 2.33€ ... ...
1 TI SN75162B ... ... ... 2.33€ ... ...



Please edit this section with your name and (public) contact details if you are interested in developing this.

  • User:Ivan747 (same nick on IRC), experience in hardware, low level firmware (but not USB). Willing to participate with the support from someone experienced in USB protocols on any kind of ARM device. Contact: ivan747[at]