LabVIEW
Error -1073807339 occurred at VISA Read
It's a timeout error. It means the device didn't send back (enough) data for the VISA Read to return with.
- Are you sure your device is even sending any data?
- Why do you think it is sending any data back?
- Did you write a command to it that you know it understands and will cause it to return some data?
- Did you write the right command syntax?
Those Arduino and similar boards only do what you tell it to do. Before they will react in any way over the serial port you first have to download a program to them (an INO file) that tells them to listen on the serial port for specific commands, do something with them on reception and then react by sending something back. Until then you can bang on the serial port of that Arduino until hell freezes over but there will never be any meaningful reaction from them.
So you downloaded a program, very likely not self made, that listens on the serial port and when seeing the "led on" or "led off" string it then sets the led on the Arduino. That is great. But your program very likely uses the function Serial.read() to read in a loop until it detects a certain character such as a carriage return and/or linefeed before processing the command.
Your terminal program adds a carriage return and/or linefeed automatically when you enter a string and then hit the Enter key (the enter key is in fact that end of line identifier). In LabVIEW you do not have an enter key to send the data but simply a string constant or control. So you need to add that character explicitly to the string yourself. Right click onto the string control/constant, Select Visible Items->Display Style. Then a glyph appears on the left side of your string frame, usually an n, indicating Normal text display mode. Right click on that and select "'\' Codes Display". Now enter at the end of the string a "\r" or "\n". Now your Arduino program most likely will understand what you tell it.
And before you can read something with VISA Read your Arduino has to write something back. Does it use a Serial.writeln() call after receiving the command and setting the LED state?
@temple wrote:
No i did not download the code i created it myself and asked a friend to help me finish it and you were right arduino reacts to my command without error after i put end of string there, thank you very much iam very gratefull for your support and maybe one last thing: It should be continous write and read but after i try to switch led off while program is running it does not work i have to abort execution and start it again to make it work. Do you think that is problem in arduino code or labview?
My magic crystal ball 🔮 is unfortunately out of operation for quite some time already. It would be needed to see the code that you forgot to attach to your post!
But my superhuman abilities tell me that it is most likely in your Arduino code. 😂
Allow me to make some tweaks to your VI.
1. I gutted a lot of the setup out. You are using the default settings, so just get rid of the junk.
2. Change your Write String to a button. Then you can define the two possible messages on the block diagram.
3. Do a read when there is something in the port. I am just using the Bytes At Port to see if there is any data. It is not used to tell the VISA Read how many bytes to read. I am just telling the VISA Read to read more bytes than I expect in a message and the termination character will do the rest for me.
4. You do not need to keep ALL of the data you read in. Just show the last message you received.
