Products > Test Equipment

Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)

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joeqsmith:
With the 607 firmware, attempting to use the external trigger with high speed commands, it does indeed put out 3 bytes onto the serial port for every trigger.   0x0d,0x30,0x0d.  The pattern repeats.  The sync output does not toggle.   

Sending the G1? to check for errors, the meter returns 19007.   Error code 19, Function Module selected not installed.  7 is function not defined.  I don't think it likes it. 

SilverSolder:

--- Quote from: joeqsmith on February 11, 2021, 12:41:06 am ---Somewhere else, interface firmware, library?   I have no idea what you are referring to.  I treat the meter as a block box.  The meter w/ 607 firmware spits out the CRs when certain binary modes are selected.  There's nothing between the meter and the PC that is adding these.   

--- End quote ---

My GPIB interface adds its own "intelligence" to the flow, I wouldn't put it past it to add CR/LF where there were none from the source.  This kind of thing can definitely cause issues.  Obviously this depends on the interface and its libraries (in the PC).

But, with a direct serial connection, I guess you can just look at it with a terminal program, with nothing in between to potentially interfere?

joeqsmith:

--- Quote from: SilverSolder on February 11, 2021, 02:50:51 am ---
My GPIB interface adds its own "intelligence" to the flow, I wouldn't put it past it to add CR/LF where there were none from the source.  This kind of thing can definitely cause issues.

--- End quote ---

Ok, you think the adapter may possibly be doing it.   I've never seen any type of USB/RS232,TTL,485 adapter that would add characters.  I require them to emulate the old time hardware serial ports.   Of course, the DSO tells the story.    Again, it has to do with the trigger setting. 

garrettm:

--- Quote from: joeqsmith on February 11, 2021, 12:41:06 am ---... The meter w/ 607 firmware spits out the CRs when certain binary modes are selected.  There's nothing between the meter and the PC that is adding these.   

--- End quote ---

I think you are correct about the <CR> terminations.

I believe the differences we are observing has to do with my serial to GPIB conversion.

My "GPIB controller" takes a specific GPIB termination (<CR><LF>) and converts it to a serial termination (<CR>). When the GPIB device sends a termination, the "GPIB controller" places the GPIB device into listen mode immediately after. When the serial device sends a termination, the controller places the GPIB device into talk mode using the "talk-back on termination." Or alternatively, does so without a termination in the "talk-back on time out" mode 100ms after the last serial byte sent to the GPIB device. I have no direct control over the talk and listen modes of the instrument. The "GPIB controller" functions are configured by dip switches only.

Currently I have the GPIB side set to <CR><LF>, if the 8506A is only sending <CR> during binary data then it is ignored and doesn't trigger the serial termination (keeping the GPIB device in talk mode). Otherwise I cannot get the DMM to automatically send data using the continuous triggering commands and I would be required to send a <CR> after each received message. If I don't send a <CR> over serial, the GPIB device will stay in listen mode. This is why I was having trouble getting the HS mode to work. I can send ! and ?, but doing so will place the DMM into listen mode, while sending <CR> will cause a GPIB <CR><LF> which exits the HS mode while the DMM is placed into talk mode immediately after.

With the current dip switch settings, while receiving binary data with PuTTY, I observe no carriage returns or line feeds, it’s just a single line of text. When I use command J, ASCII data is received the same way. Without command J, then a <CR> sets the cursor back to the start of the same line--so no infinitely long, single-line of text.

It has taken me a while to figure all of this out. So sorry about the confusion.

My bus conversion is suboptimal at best. Which is why I had to do the hacks I previously described and the strings I posted are formatted the way they were. I'll need to roll my own controller with an Arduino Micro so I can have full GPIB controller functionality.

SilverSolder:

What exactly is your GPIB adapter, @garretm?

I have a National Instruments GPIB-232CT-A here, which I actually quite like - but I have never attempted anything particularly high speed with it.

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