HP 3437A and GPIB

[c4757p]

I'm trying to get my HP 3437A working properly over GPIB, and I'm having trouble. (Keep in mind that this is my first GPIB use, and this is a very early GPIB instrument.)

I'm not 100% sure I'm reading the manuals correctly, both for the 3437A and for the National Instruments GPIB-232CV-A that I am using.

I have the 3437A configured to address 7, not talk-only. The 232CVA is also configured to address 7*, controller mode. On the RS-232 side, timeout termination (this means that GPIB switches from talk to listen about 300ms after the last byte transmitted), 9600 baud, no parity, 1 stop bit, 8 bits per char, no XON/XOFF (uses RTS/CTS instead).

*No, this doesn't mean they both think they have address 7. In controller mode, the 232CVA can only talk to one device; this is the address of that device.

It seems to work properly at first. I can transmit commands, and the instrument responds, and it transmits data back to me. However, after some time (about a minute), I stop receiving data. The 3437A still responds to outgoing commands, but I do not receive any more data until I power-cycle the 232CVA.

Also, I'm not really sure what causes the 3437A to transmit. Sometimes, it seems to give me one reading when I release the bus, and other times, it seems to just spit out a stream.

My first thought was that I wasn't fetching the data often enough, and a buffer filled up somewhere and it barfed. But the manual says that data GPIB->serial is not buffered at all, it's just pushed straight to serial, so the only buffer to fill up is on my PC, and it does not have any issues. All buffers are empty and there is no error reported. (Also, it doesn't know when the 232CVA is power cycled.)

So... problem with the GPIB-232 adapter? Me misreading a manual? Does anybody with some GPIB experience see what my problem is?

[free_electron]

your controller should be set to address 0.

look at the other settings. EOI is on ?  a lot of older machines use NEED  EOI to signify 'end of transmission'

[c4757p]

your controller should be set to address 0.

It is - this is handled automatically when it is placed in controller mode. By "address 7", I meant that it is only capable of talking to one device, set by DIP switches, and that this is the address which I have selected.

look at the other settings. EOI is on ?  a lot of older machines use NEED  EOI to signify 'end of transmission'

Hmm... the manual for the GPIB-RS232 converter doesn't say anything about EOI. It's supposed to be a "smart" converter that handles all the protocol business for you - I wonder how smart it really is. It seems to imply that all the "correct" GPIB-y stuff is done after a 300ms timeout in "timeout termination" mode, but it doesn't say if EOI is included.

I'd guess that it is on, if these machines NEED it, since it does work correctly for some time. I will have to dig out the logic analyzer tomorrow, I guess...

Sadly, this damn thing doesn't really have many settings. I can only transmit data, it handles commands by itself, with no way for me to send one manually. Probably so you don't try to circumvent the whole "one address" restriction... This might have to wait until either I get around to modifying it, or I get myself a real GPIB-USB or GPIB-PCI adapter.

[free_electron]

It is - this is handled automatically when it is placed in controller mode. By "address 7", I meant that it is only capable of talking to one device, set by DIP switches, and that this is the address which I have selected.

?!? what the hell is that ? that surely isn't a standard controller...

actually... 7 may be a bad adress to use... try 5 or so..

i believe 7 is the default thinkjet printer...

unknown to a lot of people there are a few 'reserved' adresses on gpib....

0: CIC : controller in charge
31 : ALT : alternate controller.  when this guy wants the bus he sends a special bus state. 0 and 31 then swap addresses
7 : printer
9 : plotter

i believe 18 was also a special one.... typcially used if the instrument has iBasic installed

[c4757p]

It is - this is handled automatically when it is placed in controller mode. By "address 7", I meant that it is only capable of talking to one device, set by DIP switches, and that this is the address which I have selected.

?!? what the hell is that ? that surely isn't a standard controller...

No, it's not, it's an "adapter", meant to interface one device in either direction (GPIB device onto RS-232 interface or RS-232 device onto GPIB bus). I was looking at modifying it, though, because it contains all the hardware necessary to implement a full controller, including the same GPIB ASIC they used in their more "proper" controllers.

actually... 7 may be a bad adress to use... try 5 or so..

i believe 7 is the default thinkjet printer...

Interesting. I'd be surprised if that makes a difference - this adapter seems too "dumb" to treat any addresses differently. I just left the 3437A set to the address it had when I received it, and set the adapter to match. I will try that too, though. Thanks!

[free_electron]

that adapter may be made in such a way that it converts from gpib to a serial printe.r
there were adapters made to 'capture' data only. they are not really meant to be used as a full controller.
they have barely enough capability to capture a stream if the instrument itself is a controller.


lots of 'intelligent machines' like network and spectrum analysers could be a gpib master and print or plot to a device. you would select what you were talking to and off you go.
i suspect what you have there is an adapter to convert a serial plotter or printer to a gpib device....
so it is not a full master... it is intended to behave as a slave.

[c4757p]

The manual does list a multimeter as a suggested device that it can be used with.