NI VISA read stops at zero character, returning an 0xBFFF003E error

Hi
I’m trying to read some serial data from a UUT using the NI-VISA read function. The data is mostly text but does include some control codes. The first of these appears after the ‘OK’ in the Serial Bytes window on the front panel. More text should follow but for some reason, the read function stops at the first zero character (index 144 in the Byte Array), and returns an 0xBFFF003E (-1073807298) error. I found another thread where someone had a similar problem and I’ve tried the fix for this plus a few other things, but nothing’s worked. If I use Hyperterminal, the entire data block is returned as it should be.
I wondered if this was anything to do with the 7.1 version of Labview I’m using (upgrade is on the cards). The version of NI VISA I’m running is 4.2.
Very much appreciate any thoughts.
Thanks
Bruce

The error code itself is a generic VISA error which often happens with USB to RS-232 interfaces. Does your device connect to the PC through USB as a virtual COMM port? If so what chip and Windows driver is it using?
Also your function somehow looks wrong. The only criteria for the read loop to terminate is if there is an error on the VISA read or the Teststand termination status gets true. Generally if you use VISA Bytes at Serial Port you are almost always doing something wrong! That function does absolutely not synchronize with anything in your data. You will read whatever is there at that moment and that could be a partial message, no bytes at all (LabVIEW is typically many times faster than any serial device even if it is super high speed), or multiple messages.
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

Similar Messages

VISA READ stops reading at 'zero'-char

I am reading a binairy message coming from an RFID tag that looks like this:
hex[01 09 0C B9 6E 53 0A 00 00 00 00 8B]
The Bytes at Port-property shows me the full message (12bytes) is present at the port.
Then I do a Visa_read with the 12 bytes as input, the read always comes back with 7 bytes read.
So the Visa_read stops at the ZERO characters... In a subsequent read I take the other 5 bytes.
Why does the VISA_READ stop at the ZERO character? (I am using XON/XOFF and the stop character is defined as 15, not zero!)
Check below code,
Thanks for help in advance!
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Attachments:
Visa_read.JPG ‏65 KB

Actually I bet it reads the 0x0A and you have set-up the port with the following default properties:
End mode for reads= TermChar
Term Char = 0x0A
Supress term char for reads = True
If you check the error cluster out the warning will tell you that the term char was seen, There might be more data available...
Set up the port with a F wired to ternination character enable.
EDIT: Oh the jpg clearly shows I was right make the T an F
Jeff

Increase speed visa read write

Hi guys,
I am using the visa read and write example, but I am facing some issue when using it in a larger software, and I can only receive date when the vi has been slown down (using the lightbulb).
The programme definitely works on it own with the settings defined.
Therefore, do you have any ideas/suggestions on how to increase the speed of this vi (attached) significantly? Also, it seems to create an issue with the data read
Many thanks,
Kentmey
Kentmey
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Attachments:
Read and write.vi ‏22 KB

How are you using this code inside of another VI? If you are actually calling this VI, there needs to be some changes.
1. The port should only be initialized once at the beginning of your program and clsoed once at the end.
2. There shouldn't be any need for the bytes at port. You are set up to use a termination character. So just set the number of bytes to read to something really large (like 50 or 100) and let the VISA Read stop when it finds the termination character.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
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ERROR 1073676294 ????? VISA READ...!!

Dear All
I am Writing and Reading the data from one EEPROM,interfacing with a PIC16F690,like this i am swiotching 240 EEPROM with MUX,through LabVIEW serial communication pallets,I am controlling the Reading/Writing, but some times ERROR 1073676294 ????? VISA READ...!!,once this error occurs next all EEPROM chip are not able to READ /WRITE,if unplug the powersupply and plug it back,then LabVIEW can Read/Write,i am not able to fix this error,please advise me whether problem is from LabVIEW or MICROCONTROLLER,I used delay function but also same problem.
Raikar A G

1073676294 is not an error but a warning saying that you got exactly the number of bytes you requested in the Visa read, and that there might be more bytes still remaining in a serial buffer. (Which I've always considered this a stupid warning, because as a programmer, I'm going to assume that there might be more data in the buffer than I have just pulled out.)
The warning should not cause any problems in your LabVIEW code, nor should it cause a problem with your serial communication. So if you lose communications with your microcontroller, it must be something else going wrong.

Configure VISA Read to terminate on unique character sequence

I am communicating with an instrument via a TCP connection using VISA read/write. The terminating character sequence from the instrument is "->" Is it possible to get VISA to terminate on this character sequence and basically not return these characters in a read?

No, it can only be configured to terminate on a single character. If you know that '>' will not appear in your data you can use that as your termination character. Otherwise you need to create your own read VI that will look for a sequence of characters as the termination value.
Mark Yedinak
"Does anyone know where the love of God goes when the waves turn the minutes to hours?"
Wreck of the Edmund Fitzgerald - Gordon Lightfoot

Can the carriage return within a variant be read as the termination condition for VISA READ?

Hi guys, I am trying to read a variant data using VISA READ. The VISA READ is set to terminate reading when it sees a carriage return.
Is there a chance that for the CR "encapsulated" within the variant be read by the VISA READ, and cause it to terminate?
Cheers!
Solved!
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Since with the Flatten to String you are basically sending a binary representation of the data, you are going to have problems if you have the termination character enabled since byte 13 would be part of perfectly valid data and not just represent the end of a transmission.
What you might want to do is disable the termination character. Of course now you don't know how many bytes to read. So prepend your message to write with the number of bytes that are a part of the message (string length). You may want to use two bytes, (one byte would only give you messages up to 255 characters in length.)
Now on your reading end, read 2 bytes, convert them to a number and feed that number in the next VISA read which will then read that many bytes.
For examples, look at the TCP/IP read write examples in the example finder and you'll see how they send a message with 4 bytes to tell how much data makes up the rest of the message.

How do I stop Serial "VISA Read" from giving me packets instead of available bytes.

Dear Labvillians,
Highlight:
How do I stop serial "VISA read" from giving me packets instead of bytes?
Background:
I have a system that serially publishes 14 byte packets on a semi-regular interval.
At busy times, the producer of these these packets queues the data, effectively producing super-packets in multiples of 14 bytes sometimes as large as 8 packets (112 bytes).
My protocol handler has been designed to processes bytes, packets or super-packets.
My application now has multiple devices and the order of message processing is critical to correct functionality.
My observation is that the VISA read waits until the end of a packet/ super-packet before passing the data to the application code. (See Plot Below)
My expectation is that VISA read should give me available bytes, and not get too smart for itself and wait for a packet.
I have observed this on PXI, Embedded PC, cFP and most recently, cRIO
I have experimented with the cRIO's Scan interface rate, which helps with reducing the packet backlog but doesn't resolve to sub-packet byte read.
I understand that one solution is to Write FPGA code to handle it and pass the bytes through R/T-FIFO, and there are some great examples on this site.
Unfortunately this doesn't help with non FPGA devices.
I have also dabbled in event based serial reads but it is diabolical on vxWorks devices.
Any Help is appreciated
iTm - Senior Systems Engineer
uses: LABVIEW 2012 SP1 x86 on Windows 7 x64. cFP, cRIO, PXI-RT
Solved!
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Sometimes Talking to yourself is helpful.
I hope this is a useful Nugget for someone in the future
iTm - Senior Systems Engineer
uses: LABVIEW 2012 SP1 x86 on Windows 7 x64. cFP, cRIO, PXI-RT

Why do I get a "termination character was read" warning with VISA read and TCPIP?

I am using VISA Reads with TCPIP raw sockets without issue with NI-VISA 3.0.1 but when I moved to NI-VISA 4.4 I was getting timeout errors. The timeout errors went away when I set the termination character enable property to true (which seemed to be default in NI-VISA 3.0.1), but now I get a warning stating that the "termination character was read".
Can I disable this warning? Can I set the termination character enable to default? How can I get rid of this annoying warning?
Solved!
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Hey Dagwood,
Unfortunately there isn't a way to globally change the attribute VI_ATTR_TERMCHAR_EN to VI_TRUE. I spoke with R&D about possible use of the registries and they say it's not accessible through that. To address why this change was made, the developer who made the switch isn't around anymore so I can't find his reasoning as an explanation for you. The best this for you to do in your code would be while initializing, use the VISA Property Node to make the change and until that VISA Resource is closed, this change will remain set to the value you assign. I'm sorry we cannot provide any other solution for this inconvenience. Also, if you feel this is a large burden on your programming practice you can definitely submit a product suggestion for the ability to change global default values for VISA attributes.
Thanks,
David Pratt
AES - Test Side Products
NIC

Error -1073807253 occurred at VISA Read in transient SR830.vi VISA: (Hex 0xBFFF006B) A framing error occurred during transfer.

Hi,
I am have written a program with labview to make transient c-v measurement using a stanford research SR830 lockin amplifier. The program seems to be runing fine, but sometimes it is givvibg an error:
Error -1073807253 occurred at VISA Read in transient SR830.vi
Possible reason(s):
VISA: (Hex 0xBFFF006B) A framing error occurred during transfer.
Error -1073807253 occurred at VISA Read in transient SR830.vi
Possible reason(s):
VISA: (Hex 0xBFFF006B) A framing error occurred during transfer.
but if I press ok, the program again starts running. What might be the poblem? BTW I googled a bit and I see that in the labview topic "RS-232 Framing Error with HP 34401A Mulitmeter" by pkennedy32 this is what is said about framing error:
""Framing Error" in an RS-232 context means a very specific thing - when the receiver was expecting a stop bit, the line was not in SPACE condition. This can be the result of:
1... Baud rate mismatch (although other problems would likely crop up first).
2... Data Length problem, If I send 8 data bits and you expect 7, the stop bit is in the wrong place.
3... Parity setting mismatch - If I send 7 data bits + parity and you expect 7 data bits and no parity, the stop bit is in the wrong place.
4... Mismatch in # Stop bits - If I send you 7 Data bits + parity + one stop bit, and you expect 7 data bits + parity + TWO stop bits, the second one might not be correct, although most devices do not complain about this.
But, I must say that this is the same com port setting that I use to measure c-v hysterysis, but I never gt this error there.
I attach the program herewith for your kind perusal. Please help me resolve this issue.
Thanks in advance.
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Attachments:
transient SR830.vi ‏94 KB
csac.vi ‏8 KB
sr830 initialize1.vi ‏15 KB

@Dennis Knutson you are right I checked the read indicator in backslash mode, and instead of a \n it is sending \r. So I changed the \n in my write strings to \r. But, if I keep the CLOSE VISA outside my loop instead of inside as you suggested, the termination character appears to come in the middle of the read string instead at the end. And since the read terminates at the \r so it is displaying some junk value before the \r, but if I put the CLOSE VISA outside the loop and play along with the bytes at the read buffer, I see the whole read string with the \r at the end of the string. But, whenever the values are in exponential form (when close to zero) like 6.938839 e-5, I always get a time out error whatever be the timeout that I put at the VISA initialize. And subsequently, if I stop the program and run it again the machine program hangs and I donot get any reading. Then after I close it again and start, sometimes it hangs for some more or starts working. If I put an arbitrarily large byte count at the READ VISA, then I always get the time out before the operation completed error.
@ Ravens Fan I have removed the CSAC VI altogether and taking the CH! And CH” reading separately, instead as one string. So, no more issues with that.
I use the control at the delay so that I can choose how much delay I want to set, and I use the math operation because I am using adding up the delay time to keep track of the time elapsed. Because in the end I have t plot a time vs. CH! And CH” readings.
I am not sure but probably I am making some silly errors. Please help me out.
Attachments:
transient SR830-2.vi ‏103 KB
sr830 initialize1.vi ‏15 KB

VISA read timeout

I dont know why im getting a timeout error at the VISA read function(error says "timeout expired before operation completed"). I made sure the Labview serial port and my devices serial port are configured exactly the same. I even tested hyperterminal with the same port settings as in labview and it works perfectly but my labview program gives me an error. My device terminates each command it sends with a carriage return so i set up VISA READ to stop reading data when it encounters the CR character. I also made sure the carriage return was infact being sent by my device. Any thoughts?
Solved!
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I think it's not seeing your termination character on the read and/or write. When I send a string to the serial bus, I always use "Concatenate Strings" to add the appropriate termination character(s) to the end. Assuming your read termination is CR/LF, I've always had better luck stopping on the LF and stripping the CR with "Trim Whitespace."
Also, don't be afraid of making the timeout a second or two. If everything is going right, it will (normally) give the serial port plenty of time to complete its operation, but if things are going wrong, it will give you time to "notice" something is wrong.
Bill
(Mid-Level minion.)
My support system ensures that I don't look totally incompetent.
Proud to say that I've progressed beyond knowing just enough to be dangerous. I now know enough to know that I have no clue about anything at all.

VISA Read and Bytes at Port Timing Question

Hi,
I have a question that doesn't seem to be documented in the VISA Read function help. My application normally queries a serial instrument, waits, and then reads the port (with Bytes at Port property node wired to the byte count input of the VISA Read). However, I also need to be able to handle strings received from the instrument asynchronously without my vi requesting any data. So in the False Case in my vi (the True Case is where I write a command to the instrument) I have a Bytes at Port property wired to the VISA Read function's byte count input without using a VISA Write. This works fine if the \r\n terminated string is sent in one packet. However, sometimes there is a slight delay (only a few milliseconds) between characters. When that happens, the VISA Read returns, but I don't get the entire intended string. (Of course I know I have to keep reading in a loop until I get the \n and then assemble the received characters (sub strings) into my complete string for processing.)
This is my question: What is the time delay between characters at which the VISA Read terminates? This is not specified. I assume it could be as little as just slightly more than 1 stop bit at the baud rate being used. Does anyone know? NI employees?
When a string of more than one character (byte) is sent, as soon as the stop bit time has expired, the next start bit is normally sent immediately. Is it possible that if the next start bit doesn't come by, say, the mid-bit position time at the baud rate being used, the VISA Read returns immediately? Or does it wait at least 1 character time (at the baud rate)? This should be documented. Furthermore, for future versions it might be useful to add an input to the VISA Read to specify in milliseconds how long to wait AFTER the 'byte count' number of bytes have been received before returning the string (or character).
Thanks for your help.
Ed

I looked up the PC16550D data sheet (http://www.national.com/ds/PC/PC16550D.pdf). On p. 19 it says:
When RCVR FIFO and receiver interrupts are enabled, RCVR FIFO timeout interrupts will occur as follows:
A. A FIFO timeout interrupt will occur, if the following conditions exist:
    - at least one character is in the FIFO
    - the most recent serial character received was longer than 4 continuous character times ago (if 2 stop bits are programmed the second one is included in this time delay).
    - the most recent CPU read of the FIFO was longer than 4 continuous character times ago.
The maximum time between a received character and a timeout interrupt will be 160 ms at 300 baud with a 12-bit receive character (i.e., 1 Start, 8 Data, 1 Parity and 2 Stop Bits).
B. Character times are calculated by using the RCLK input for a clock signal (this makes the delay proportional to the baudrate).
C. When a timeout interrupt has occurred it is cleared and the timer reset when the CPU reads one character from the RCVR FIFO.
D. When a timeout interrupt has not occurred the timeout timer is reset after a new character is received or after the CPU reads the RCVR FIFO.
So, this UART uses 4 character times to determine that no more characters are coming in. And the delay is baud-rate dependent. This makes sense because I see that at, say, 115200 baud I receive more "partial strings" than I do at 9600 baud (where the sending device has more time to send the next character)!
Kudos for making me investigate this further! Thanks for listening. Hope this may help others in the future.

Visa Read Timeout Occurs with multiple Reentrant VI Calls

I have written a test application in Labview (6.1) which will be used to test (burn-in) up to 15 serial instruments through a 16 Port USB->RS232 Hub. Here's how it works:
When the App loads, I am transmitting a Connect command to each of 15 com ports (one-at-a-time) using VISA. If I receive the proper response from the unit on that port, I add the port to an array and continue on to the next system. Once I've found all systems on the hub, I wire my array of active Visa references to a for loop in which I open up to 15 reentrant VIs which will run in the background in parallel. Each of these reentrant VIs (all are idential with the exception of the Visa Resource they use) running in the background are sending commands to the the respective instrument and receiving a response. One Function in particular "Get Unit Status" is important and the response determines whether or not the instrument is functioning correctly. Here's the problem -- In my Main Loop, I am continuously acquiring indicator values from each of the reentrant VIs that are running in the background. After a period of time (not consistent) I will lose communication with a port (the symptom is no response from the unit). I've looked closely at the COMM engine I created and found that the Visa Write function is completing without error, then when I perform a Visa Read I immediately get the "Timeout occured before operation completed" error (please keep in mind that this occurs after 100-5000 successful attempts at writing/reading). Eventually another port will drop out, followed by another. This seems to stop occurring and the remaining systems run to completion without a problem.
Some background on what how I'm setting up my Visa Sessions...
When I originally scan for systems (before I load and run the Reentrant VIs)
- Init Visa Port
- 19200, 8, N, 1
- Use Termination = True
- Timeout = 400mS (I've tried larger values already) 400mS should be plenty
- Termination Char=13 (/r)
- Open Visa Session
- Visa Write "CONN18/r" (the command required to connect to my instrument)
- Visa Read with 1 for requrested byte count to read 1 byte at-a-time, concatenating the results until /r is received (or 1000mS timeout occurs -- this is not a VISA timeout) I've also tried 16 for requested byte count and just waiting for Visa to timeout -- both methods work.
Once all 16 ports are scanned I Close ALL of the ports using the Visa Close Function.
It is important to know at this time that I "AM" using proper wiring flow to ensure open occurs before write, write occurs before read, etc.
I'm assuming at this time that all of my Visa sessions are closed.
On to the Reentrant VIs:
Inside each reentrant VI I first Initialize all of my variables and Init/Open a 'New'? Visa session using the same parameters mentioned above.
Then I enter the "Run" case structure where all of the communication begins.
I am using the same Communications Engine to operate the instrument as before (the only difference being that all of the VIs in the comm engine are now reentrant and operate at higher priorities) I have actually saved two different versions of the engine (one for the reentrant calls and one for when I first scan for systems from my Main GUI).
When I init the reentrant VI, I am placing the Duplicate Visa Resource output of my Visa Open Function on a shift register. When I enter the Run case, it takes the Resource from the register on the left, wires through any Comm Engine Vis then back out to the shift register on the right and keeps going for a 12-hour period or until "Get Unit Status" has returned 60 naughty results.
On my Main GUI I am continuously (every 500mS) I am Getting certain Indicator Values from each reentrant VI AND I am also setting some control Values on each reentrant VI. There is no VISA interaction between each Reentrant VI, and the Main GUI.
As I said earlier, up to 15 systems will run for a time, then one will stop responding, followed by another, and another until a few remaining systems will run to completion.
Any advice as to why I'm encountering the timeouts with the VISA read fucntion as I have metioned would be appreciated. I managed to find one suggestion which uses the Bytes at Port function to ensure there is data at the port before doing a Read otherwise, skip the read and retry the whole operation -- I haven't tried this yet.
Sorry for the wordiness of my question. If anyone would like some screen shots of portions of my code (I can't submit the actual code because some of it is confidential) I'd be happy to post them.
Doug.

Hi Doug,
The first thing I would recommend is the solution you have already found, to check and see if there is data at the port before attempting a read. I would be interested to see if this will solve the problem. Does there seem to be any trend to which ports have this timeout error? How many ports does it cut down to before operation seems to continue as expected? Does this number vary, or is it always the same number of ports? I think the best thing to do will be to identify constant attributes of how the error is occurring so that we can narrow it down and see what is going on.
John M

VISA Read over USB Problem: After a while the xBFFF0015 Timeout Error occurred

Hi,
I have trouble using labview with my non-NI USB device:
The device is an analog input DAQ board. I was able to setup communication with the board using a VISA driver specifically created for this board and direct FW calls using the product's firmware specification provided by the manufacturer.
This method has been working pretty good so far, but when I try to get large amount of data (64k samples @100ksps), the VISA Read returns the 'VISA: (Hex 0xBFFF0015) Timeout expired before operation completed.' error.
Please see the attached screenshot of the block diagram for details.
First, an 'analog input scan start' command is sent to the DAQ device, and then the vi tries to read all collected data from the device, once the right amount of data retrieved, or no more data is available the data collecting process (the while loop) ends and an 'analog input scan stop' command is sent to the DAQ device.
The data collection starts with no problem, but after a while, in loop# 400, the VISA Read hangs and then returns the error mentioned above.
I tried to increase the time out value, but it didn't help, the error occurred after the same number of loops, the VISA Read got hosed and the error occurred after the longer timeout expired.
I also tried to add some delays in the loop, but it didn't help either.
I am not sure what do I miss here and I would highly appreciate if anyone could give me some guidance how to solve this issue.
Thanks,
John
Attachments:
usb-read.png ‏18 KB

I just wanted to specify that this is not an NI board avoiding to make people think this is a hardware issue. And I think that the rest of the code is irrelevant in this case.
I believe that I don't use the VISA functions correctly. I assumed that someone who used these functions before would be able to point out the obvious steps missing in the data collecting process using the VISA functions.

Read in Binary form in VISA read function

Dear All,
I have connected my Device to the serial Port. and data read from the buffer is stored in text format. I want to view the data in binary format .
Actually, i have performed the same function in Visual Basic. there also if i view the data in text format, it shows some junk values. but if i view the data in binary, it shows the actual data coming from the instrument .
I dont know how to modify the VISA read function. can any one pls tell me how can i read the data in binary format?
Thanks
Ritesh

Oops! No it didn't.
Lab VIEW 2012 (if that makes a dif)
I'm using the VISA Read function to take ADC readings in from a microcontroller. The VISA Read function outputs the data as a string. Easy to convert the string to U8, either with the conversion function or type cast function, and works great except for a tiny corner case when the ADC reading is zero. The VISA Read function treats the 8-bit zero reading as a null character and strips it out.
Apparently, since this is done by the VISA Read function as it's building the string, type casting and or converting the output string from the VISA Read function doesn't "bring the zeros back".
I've tried setting the VISA property "Discard NUL Characters" to false, and that didn't seem to help.
My current work around is just to never have the micro send a zero ADC reading.
Anyway, I'm a Lab VIEW noob, so while this isn't essential to my project, I remain curious about how to send Lab VIEW serial data that isn't automatically considered characters, thrown into a string with all the zeros stripped out.
Regards,
Who

How to run vi continuously when VISA read timeout happens

Hello,
I am using LabView 2010 to read an Agilent 6000 series Oscilloscope. The Oscilloscope reads data from another experimental machine which fails occasionally due to sample failure. When the machine fails, it stops sending signal to the oscilloscope and leads to the VISA read timeout error and the whole vi is terminated. Is there a way that I can continuously run the vi when the error happens? For example, when the error happens, it stores the error in the error wire. When the vi read the error code from the wire, it sends a command to stop my experimental machine then stop the vi.
So far, it just simply stops during executing the visa read function. In this case, why do we have error in and out? The vi simply stops when the error happens.
Thanks
Lawrence
Solved!
Go to Solution.

I'll start of with automatic error handling. By default, LabVIEW enables the automatic error handling. So consider the case like the one below,
If let's say the VISA Read returns an error, but you did you pass the error information to VISA Close, what will happen is that LabVIEW will highlight the VISA Read (since the error comes from that function), pause the execution at the VISA Read and an error dialog box will appear. From the dialog box, it will prompt to either continue (Move on to the VISA Close) or stop (LabVIEW will stop the VI at VISA Read)
Now, consider another scenario like this,
By passing the error information from one function to another, let's say if VISA Read returns an error, that error will pass to VISA Close and finally to Simple Error Handler.vi. So Simple Error Handler will generate error dialog box after all the VISA operation is completed. This is called manual error handling (It can be enabled by just wiring the error information from one function to another and terminates at Simple Error Handler).
http://www.ni.com/gettingstarted/labviewbasics/handlingerrors.htm
As for VISA Close, here is the information about VISA Close.
http://zone.ni.com/reference/en-XX/help/371361K-01/lvinstio/visa_close/
See that button on the left side of this post...
If you feel my post is helpful, all you need is just (at most) 2 seconds to click that button, to show your appreciation. Thank you~~

NI VISA read stops at zero character, returning an 0xBFFF003E error

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