336540Design 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 11. 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.