LabVIEW
Write data read from a PLC to an EXCEL file continously
I shall begin and end with the same request. Here it is. Please, please, please, hire an Alliance Member who is a Certified LabVIEW Developer (like me) to help you even if just for a single day. Have the CLD write a few VIs for you, and then refer to those VIs for style guidelines and techniques. Having said that, my compliments to you for using 7.0.
Now, we're in the middle so I'll address your problems.
1. You say you want continuous storage of data, yet your dataflow does not allow it. You have all the datasocket reading contained in a while loop. The output of the while loop is an array on which the Excel writing loop depends. The Excel writing cannot happen until after your datasocket reading completes due to that data dependency. A central theme of LabVIEW is the concept of data dependency. You must learn it, use it, and love it.
2. You have branched the ActiveX reference to Excel several times and distributed it to asynchronous parallel while loops. There is no guarantee that those loops will all execute at the same rate. Also, it makes you code very hard to interpret. You can achieve a more desirable result by using in-line VIs. I�ll be extra-nice and show you what I mean in the attached example.
3. The branching of the ActiveX reference is bad, but the multiple closing of Excel is worse. You only have to close the references, workbooks, and worksheets that you open, not each branch of those references. You�ve got lots of redundant code there that will generate errors. You would see those errors if you wired up the other instances. Tisk, tisk.
4. You have VI-itis: Inflamation of the VI. We must all strive to keep diagrams compact and readable. The guideline is that if you cannot manage to fit the diagram on one screen, extend in one direction only. It makes debug / feature addition orders of magnitude faster and easier.
So, check out the example I whipped up based on your VI. Now, some disclaimers; I only spent about 10 minutes on the example. It should work, but there may be something I missed. Either way, it should give you a guide. Also, if I seem harsh, it�s only because I care. I use LabVIEW every day, and I like others to realize its full potential. When wireworkers turn out poor code, it hurts us all. You have great potential and have come a long way. Keep an open mind and keep tinkering. That goes for all of you!
Again, try to work with an Alliance Member. We do this stuff every day, and most of us are good at it.
Sincerely,
Daniel L. Press
Certified LabVIEW Developer
Director of Engineering
PrimeTest Corporation
www.primetest.com
Now, we're in the middle so I'll address your problems.
1. You say you want continuous storage of data, yet your dataflow does not allow it. You have all the datasocket reading contained in a while loop. The output of the while loop is an array on which the Excel writing loop depends. The Excel writing cannot happen until after your datasocket reading completes due to that data dependency. A central theme of LabVIEW is the concept of data dependency. You must learn it, use it, and love it.
2. You have branched the ActiveX reference to Excel several times and distributed it to asynchronous parallel while loops. There is no guarantee that those loops will all execute at the same rate. Also, it makes you code very hard to interpret. You can achieve a more desirable result by using in-line VIs. I�ll be extra-nice and show you what I mean in the attached example.
3. The branching of the ActiveX reference is bad, but the multiple closing of Excel is worse. You only have to close the references, workbooks, and worksheets that you open, not each branch of those references. You�ve got lots of redundant code there that will generate errors. You would see those errors if you wired up the other instances. Tisk, tisk.
4. You have VI-itis: Inflamation of the VI. We must all strive to keep diagrams compact and readable. The guideline is that if you cannot manage to fit the diagram on one screen, extend in one direction only. It makes debug / feature addition orders of magnitude faster and easier.
So, check out the example I whipped up based on your VI. Now, some disclaimers; I only spent about 10 minutes on the example. It should work, but there may be something I missed. Either way, it should give you a guide. Also, if I seem harsh, it�s only because I care. I use LabVIEW every day, and I like others to realize its full potential. When wireworkers turn out poor code, it hurts us all. You have great potential and have come a long way. Keep an open mind and keep tinkering. That goes for all of you!
Again, try to work with an Alliance Member. We do this stuff every day, and most of us are good at it.
Sincerely,
Daniel L. Press
Certified LabVIEW Developer
Director of Engineering
PrimeTest Corporation
www.primetest.com
