This instructable shows how to create a GPIB shield for "Engadino" and how to obtain as final product an USB to GPIB adapter.
Step 1: What Is GPIB?
" IEEE-488 is a short-range digital communications bus specification. It was created in the late 1960s for use with automated test equipment, and is still in use for that purpose. IEEE-488 was created as HP-IB (Hewlett-Packard Interface Bus), and is commonly called GPIB (General Purpose Interface Bus)...
In the late 1960s, Hewlett-Packard (HP) was manufacturing various automated test and measurement instruments, such as digital multimeters and logic analyzers. They developed the HP Interface Bus (HP-IB) to enable easier interconnection between instruments and controllers (computers and other instruments)......"
With the time a lot of companies producing test and measurement devices embedded the GPIB interfaces in their products. Until now come laboratory devices having this interface. The GPIB interface did the work of the test engineers more easy and attractive. It was possible (and still it is!) to control a plenty of laboratory devices (multimeters, oscillators, functional generators, oscilloscopes, power supply sources...etc) connected at one GPIB bus using a single PC host as controller. The company "National Instruments" has developed an easy to use, powerful and flexible software called "Labview" to control the test and measurement devices, to acquire automatically the measurement data and to process it mathematically. Similar software tool called "Vee" is created by "Agilent Technologies". The only needed to build the GPIB network was GPIB card inserted in the PC and cables. Further even this card became unnecessary. USB to GPIB adapters could work as well.
The main problem if an electronics hobbyist faces, when he wants to build his own GPIB network, is that these USB to GPIB adapters are expensive. NI sells their for ~ 500 USD. The adapter designed by Prologix is cheaper (150 USD), but still not very comfortable for home users.
The easiest solution in this case is the DIY USB to GPIB adapter. The adapter, which I want to present to you, is based on the "Pinguino" clone "Engadino" with additional shield.
Here I want to declare, that the design is not fully my work. The shield is re-arranged schematics created by Ralf Tralow , which was adapted to pass to the "Engadino" board. The software is also his creation. It can be downloaded from here.
The shield together with the "Engadino" board costs ~ 30 USD, what make this solution pretty attractive, having in mind that the "Engadino" board can be used also for other projects.
Step 2: The Design Data...
The part list for the shield:
1 x 24pin GPIB connector (my connector is TE product. The PCB is designed for female type of the adapter, but this is not problem, because the GPIB cables are done in the way that both types of connectors can be stacked one over the other).Such kind of connectors can be found also in ebay.
2 x 8x10 KOhm resistor network
2 x 470 Ohm
1 x red LED
1 x yellow LED
1 x single row pin header
For the adapter I did not use the original "Engadino" board, but specially prepared dedicated board.
The reason for this was, that I wanted to lock this board in the USB to GPIB adapter and to not use it more for other purposes.
In this way I could simplify the board and to reduce the adapter costs. Because the adapter was intended to be used only connected to the USB of the PC, all devices used for alternative power supply were removed.
The protection resistors at the outputs in the original "Engadino" with values 470 Ohm were replaced with 100 Ohm ones.
I decided also not to burn a bootloader in the PIC18F2550 chip, because it was not needed - it had to have only one function, and once programmed has to be used life long. This allowed me to omit some additional parts ( the switch S1, one of the LED's and one resistor).
On the picture you can see the not fully populated "Engadino" board. Now I think, that I could omit also the female pin headers and to use only long pins soldered between both boards.
Step 3: The Schematic of the Shield
The shield schematic is shown on the picture. For DIY enthusiasts I have attached the pdf files, which can be used for toner transfer. There are two metal layers used, but it can be used only the singlesided PCB - the top layer connections can be replaced by wire bridges.
Step 4: The Soldered Shield Board...
I have ordered factory made PCB's. The soldering is very fast and simple.
Step 5: The Whole Adapter Assembled and Connected
Step 6: Software and Driver...
The testing software can be downloaded from here : http://sourceforge.net/projects/usbgpib/files/ (thanks to Ralf Tralow).
The Windows driver needed for the work of the adapter is available at the same link.
A bare PCB of the shield can be ordered at e-mail address firstname.lastname@example.org agianst 10USD (delivery included). Both PCB's (Engadino+GPIB Shield) for making GPIB adapter cost 16 USD (with shipping costs included)