Smart Doctor Assistant Kit using LabVIEW - Final Project

It's nigh on impossible to debug from images.  Use NI I/O Trace, installed with LabVIEW, to see exactly what is being sent to and read from the device.  Without seeing data on the wire that is entering the "= E" check, or the case structure I couldn't begin to tell you what is happening: if you've put a breakpoint on the data wire inside the case and execution stops there, then it's obviously getting into the Case structure which at least tells you that it's getting in.  Have you tried running it just capturing ECG data and not generating the other data?  That would at least focus debugging on to that one piece of data.

In your code, are you sending an empty string to Visa Write or a Space character?  

You shouldn't have to use the "Bytes at Port" property, just wire a value that is greater than the bytes expected: Visa Read will always return when it has read a termination character, sent by the device (or an error or timeout or number of bytes specified but let's assume none of those happen.)  If you say read 100 bytes, but the device only sends 5 then it will return after reading 5 bytes if the last one was a terminating character.  Hope that makes sense.

Hey thanks buddy for the suggestions, really appreciated. I tried with lowercase letter as well but i don't think that will be an issue. I tried placing a breakpoint also. Although i have already placed an indicator at visa read out if you have noticed in the bottom left of the front panel named as Output. Data is available at that case but it shows " a character was not read from the output before next character arrived."

Looks good, nice idea.  With the Waveform, I notice you use an uppercase E rather than a lowercase one - all your other characters are lower case.  Did you try putting a breakpoint on the wire leading to the Scan Value function to see if it's actually getting into that case?

I don't know if you realise, but there is a more efficient way of managing your cases.  At the moment, you have 5 case structures, and the one that runs is determined by a check against the leading character in the data.  You could use just one case structure and do this:

• wire the output from the replace substring (the one that you currently have wired to an = block) to the case selector terminal - you don't need the = block.  Then you can change the two entries that are created automatically so that one is just "default" (an error case because it should never get called) and the second to "t".  Then add cases for your remaining letters (right click on the case structure edge.)  
• Where you currently have the output of replace substring entering each case into a Scan Value block: pull that scan value out of the case structure and instead wire the output of the Scan Value into the new case structure.  This bit of code is the same in each of your current case structures so with just one case, it doesn't need running 5 times.  Hope that makes sense?
• In each case in the case structure wire the terminal from the Scan Value to the indicator it is used for.  LabVIEW will run the case that matches the input letter, cases don't have to be just "true" or "false".