Design of Bio-Medical Virtual Instrumentation Tutorial 2

Outline Debugging techniques Structures: – While loop – For loop

Debugging Techniques Broken VI

Debugging Techniques Non broken VI – Execution highlighting- generates an animation of the execution of the block diagram. – Single stepping – Breakpoints – Probe tools – helps checking intermediate values in a VI that produces unexpected results

Exercise 1 1. What is the problem with the next diagram? 2. Fix the following VI:

Structures

While loop Analog to: Repeat (code) ; Until Condition met; End; code Condition met? end No? Yes

Iteration terminal – contains the number of completed iterations. Starts at zero. Continue if true – the while loop executes its subdiagram until the condition teminal recieves a FALSE value. Stop if true - the while loop executes its subdiagram until the condition teminal recieves a TRUE value. While loop always executes at least once!

Structure Tunnels Tunnels feed data into and out of structures. The tunnel apears as a solid block on the border of the While loop. What happens if we run the VI with a Boolean value of False?

For loop Analog to: N=100; i=0; Until i=N; Repeat(code); i=i+1; End; N=100 i=N? end No? Yes i=0 Code i=i+1

Iteration terminal – contains the number of completed iterations. Starts at zero. Count terminal – input terminal whose value indicates how many times to repeat the subdiagram

Conditional terminal to a for loop You can add a conditional terminal to configure a For loop to stop when a Boolean condition is met or an error occurs. The For loop will execute until the condition occurs OR until the all iterations are complete.

Exercise 2 What will the indicator display after this program has run?

Timing a VI Wait until Next ms Multiple – monitors a millisecond counter and waits until the millisecond counter reaches a multiple of the amount you specify. Wait (ms)- waits until the millisecond counter counts to an anount equal to the input. Time elapsed- the amount of time elapses after the specified start time.

Iterative Data Transfer – Shift Register Used when wanting to pass values from previous iterations through the loop to the next iterations.

Exercise 3 Create a VI which raffles a random number (between 0-1) in each iteration and compares it to the number from the last iterations If the current random number is smaller than the previous one, stop the loop. Returns the number of iterations.