How to measure execution time? And code size?
 

Can someone describe a simple way to measure how much of the 26 ms time budget is being used? As I add code I would like to know how close I am coming to the limit.

Also, how do I know how close I am to the memory limits for code and data?

Thanks all,
Norm

Re: How to measure execution time? And code size?
 

Add a breakpoint at the top of process_data_from_master_uP and at the bottom. Then use the simulator and the stopwatch to calculate the time different between the 2 breakpoints.

For the memory thing, use the simulator and just look at the memory map of program and data memory.

Re: How to measure execution time? And code size?
 

What simulator? I tried one in mplab, and it got stuck in one of the transmission loops!

Re: How to measure execution time? And code size?
 

To measure the time, you should toggle a digital I/O pin every cycle. Then, hook an oscilliscope up to that pin. Using the scope, you can measure your timing very accurately.

Some example code (place this at the very beginning of your code):

static char TimingFlag;

if (TimingFlag)
TimingFlag = 0;
else
TimingFlag = 1;

Then immediately set the digital I/O pin equal to TimingFlag.

This code will produce a square wave on the scope. The time that the wave is high (or low) is your cycle time. I hope this helps.

-Chris

Re: How to measure execution time? And code size?
 

For the timing I set an internal timer and initialize the timer at the start and read it when it comes around again. You can use clock ticks or convert it to ms. I wouldn't use the MPLAB SIM for this.
For the default code you get 112,840 to 112,892 loops per second or ~42 (THE_ANSWER) ticks per loop for the basic default program (results may vary).

There are a couple of ways to check memory utilization.
1) When you open the .hex file in the IFI_Loader there is a text string at the bottom of the IFI_Loader window that tells you how much space the .hex file uses. For instance, the FRC default code will show:
"Total Bytes 2C90, Erase Size B5, Flash 800-3510, MemSize 2D10"

2)A memory map can be generated by MPLAB whenever you compile your code. You have to turn it on by going to Project -> Build Options... -> Project then click on the "MPLINK Linker" tab, then click on "Generater map file". After you build your project look in the project directory for a text file ending in ".map" just a little way down the file it will have a section that looks like:
This gives you the program or rom space used. For the data or ram space it's a little harder. After the section above all space used will be listed by address. You'll see your familiar variables listed. You have to check the maximum addresses used by the data portion of your code.

Re: How to measure execution time? And code size?
 

The loader reports some information on program size. I'm not sure what it all means, but it's there.

Re: How to measure execution time? And code size?
 

Yeah, the simulator they have is fairly worthless.

Re: How to measure execution time? And code size?
 

measureing timeing on the simulator wont tell you what you want to know, because the SW will be running on your PC, not on the target system (the RC) which is what really matters.

Re: How to measure execution time? And code size?
 

I don't know squat about the Simulator, but I think Mr. Lundy may have been saying that the Simulator is "clock speed-aware". It may know, or can be told, what the processor's clock rate is. I guess if the code doesn't use interrupts, that would be enough to determine the number of processor clock cycles between two points in the code.

realExecutionTime = simulatedClockCycles * realClockPeriod

I'll have to have a closer look at the simulator. At this point I feel like I don't have time to go up another learning curve. But I should probably do it anyway...

Re: How to measure execution time? And code size?
 

Oh yeah, I forgot one thing.

My first post only works if you're running the loop time as fast as possible. It doesn't work if you're setting your loop time with an interrupt. To measure this way do the following:

1) At the VERY BEGINNING of your loop, set a digital I/O pin high.
2) At the VERY END of your loop, set the same digital I/O pin low.
3) Measure the pin voltage on a scope.

The amount of the the pin stays high is the amount of time that your code takes to run.

(By the way, this is how code time is usually measured in industry.)

Re: How to measure execution time? And code size?
 

Ooo, I like the idea of using a scope. Technology that I understand!

But I think the code you suggest may not give me what I want. I think the code you suggest would toggle a pin with every 26 ms cycle of the code, so the high and low portions of each square wave cycle would each be 26 ms, regardless of how long my code was taking.

Your code was:


How about this instead, in main.c. Note the two lines with ***:

Re: How to measure execution time? And code size?
 

remember that you have to have the constant "_SIMULATOR" defined while compiling code for the simulator - this keeps the program from bogging down in the transmission loop.

Re: How to measure execution time? And code size?
 

Yeah I didn't mean an actual stopwatch, there is a function in the simulator that keeps track of time based on chip speed. It's called the "stopwatch".

But the oscilloscope idea sounds easier (assuming you have an oscilloscope you can use).

[EDIT]Oops...

Re: How to measure execution time? And code size?
 

i'm guessing you mean "oscilloscope". :)

Re: How to measure execution time? And code size?
 

engineers have to learn to listen to what people mean, not what they say :)