Products > Test Equipment
Tektronix TDS754C not communicating over GPIB in unprotected mode
44kgk1lkf6u:
The screenshot shows that the off bus option is selected. The oscilloscope is not supposed to respond on GPIB in this state. You have to make sure the "Talk/Listen" option is highlighted instead.
TERRA Operative:
Here are my settings that work for me with an Agilent 82357B USB-GPIB adapter, and a National Instruments USB-GPIB-HS adapter (I used the NI adapter to capture the screen shot).
As 44kgk1lkf6u mentioned, make sure 'Talk/Listen' is selected at top right. I also suggest setting the GPIB address to 1 (or not zero at least), the Keysight Connection Expert software didn't care, but the absolutely bloated mess of total crap that is the National Instruments software package only worked when I set the address from 0 to 1.
amaschas:
I still don't really understand how the GPIB settings work, but since my scope is able to communicate in unlocked mode I figure the port must be active and not set to talk only? Here are the settings I'm actually using, just uploaded that previous image as an example of how confusing that settings screen is.
Another interesting development. I ordered am NI GPIB/USB adapter a while back and it showed up. I started poking around with the NI software, and as expected when I scan for instruments in locked mode it successfully finds the instrument on address 1. However, when I toggle the unlock switch and scan for instruments, the NI software picks up an instrument on address 29 what will not respond to *IDN?. I have read suggestions elsewhere that some of these scopes use different addresses for GPIB in unlocked mode (this guy here for instance: https://www.eevblog.com/forum/repair/tekfwtool-for-tds540c-firmware-upgrade/msg2845956/#msg2845956), but since the instrument still is not responding to *IDN? I'm not sure whether its actually finding anything? Here's what I see trying to connect to the instrument.
I'm wondering if this could be an issue with corrupted firmware? I have a parallel effort going to extract the firmware and calibration data using the floppy disk tool, which appears to have succeeded but as I have don't have any machines with an old enough OS to read a floppy without a media descriptor byte, I'm trying to get my hands on an old laptop that can run Windows XP, which at the very least comes with the tool that can add the MDB. Once I have a firmware backup I'm confident in I'm going to pull the two NRAMs off the board and solder in headers, and I'll maybe try restoring the firmware. My understand is that the scope boots from some kind of bootloader in unlocked mode however, and I don't know if the firmware has anything to do with that.
picburner:
An explanation for the lack of response to the *idn? command could be this (taken from the "C" code of the Tektool utility):
--- Code: ---#if 0
/* Test GPIB communication */
/* WARNING - DOES NOT WORK WHEN IN NVRAM-UNPROTECTED MODE ON CERTAIN MODELS! */
ibwrt (Dev, "*IDN?", 5L);
if (ibsta & ERR)
{
GPIBCleanup(Dev, "Unable to write to device");
return 1;
}
ibrd (Dev, buf, 101);
if (ibsta & ERR)
{
GPIBCleanup(Dev, "Unable to read data from device");
return 1;
}
#endif
--- End code ---
If your firmware is corrupt you will be warned during boot, there is an integrity check for this.
TERRA Operative:
If you need clean firmware dumps from the NVRAMs, I can probably sort something from one of my spare scopes and send through the files.
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