Arduino Cpu Utilization - how?

Forum 2005-2010 (read only) Software Syntax & Programs
1

Hi,

I know there are various memory available routines going around, but I wondered if anyone has come up with a way to measure the main loop time.

We used to have it on our Z80 (Z280) based Cpu's years ago and it measured & displayed the main loop in uS......very handy for seeing what was going on.

Any ideas?

Ian.

2

Easy enough to do, but with synchronous serial I/O, the reporting affects the results.

3

if you have a scope or frequency counter, you could turn a pin on and off (set the port bit, not with digitalwrite) and measure the frequency.

4

Give this a try...

unsigned long LastMicros;

void setup( void )
{
  Serial.begin( 9600 );
  LastMicros = micros();
}

void loop( void )
{
  unsigned long ThisMicros;
  unsigned long Delta;
  
  ThisMicros = micros();
  Delta = ThisMicros - LastMicros;
  LastMicros = ThisMicros;
  Serial.println( Delta );
  
  delay( 1001 );
}
5

Hi all,

Managed this via a counter in my main loop, then every 40mS (my interrupt loop) measuring how many main loop counts occurred and then translated that into mS.

0.77mS per main loop.

Ian.

6

0.77mS per main loop

That sounds an awful lot - I assume your serial print time is included in that?
[edit]Fairly empty "loop", like CodingBadly's gives about 8.18us, averaged over 1000 loops[/edit]

7

Not using serial print at all.......my project has an 4*20 LCD, ethernet shield (web server), servo drive, analogue inputs, digital I/O etc.......550 lines of code.

Using a bunch of other libraries as well, including eeprom.h, pgmspace.h.

This is why I wanted to measure the main loop time.

It's my first Arduino project and I wanted to push it to the limit to see what's capable and what's not. I'm already at the limit of sram.

I guess my next test will be to write a simple sketch with everything ripped out and measure the loop time at it's fastest.

Ian.

8

Not using serial print at all

Then how do you know how long it took?

9

The 4x20 LCD, perhaps?

10

Does that involve serial communication? Mine does.

11

That sounds an awful lot - I assume your serial print time is
included in that? Fairly empty "loop", like CodingBadly's gives
about 8.18us, averaged over 1000 loops

I agree 0.77mS is a lot, so I moved some code from my main loop to my 40mS interrupt loop and immediately it's down to 0.07mS (70uS).
It was moving the analogRead's that gained the speed. I didn't know they were that slow.

Does that involve serial communication? Mine does.

See:-
#include <LiquidCrystal.h>

Ian.