The big difference between AVR simulator and Real hardware

dabatek · Joined: 31 Jul 2013 Posts: 32 Location: Serbia

Please help,

I work on some time critical project and I found that time (cycl.) need for
GETADC is not like in AVR simulator. With DSO I measured 80 times bigger value !

This is simple code for measure purpose:

$Regfile="m328pdef.dat"
$Crystal=16000000
$hwstack=32
$swstack=8
$framesize=50

Config PortD.2 = Output

Config Adc = Single , Prescaler = Auto , Reference = Avcc

Start Adc

Dim W As Word

portd.2=1

Do
portd.2=0
W = Getadc(0) ' in AVR Simulator need 0.00125ms, BUT IN REAL HARDWARE WITH DSO I measured ~ 0.2ms !!!
portd.2=1
waitms 2
Loop

End

Where is the problem ?

Best regards

Z.D

(BASCOM-AVR version : 2.0.7.9 , Latest : 2.0.7.8 )

MWS · Joined: 22 Aug 2009 Posts: 2262

Simulation time is likely pure execution time of ASM code and does not reflect actual conversion time.
If it's time critical, then the auto setting of config adc and the command GetADC is probably not the right thing anyway.
Reading the data sheet and manually setting the prescaler is self-evident.

The "auto" setting chooses the greatest ADC-prescaler and such the slowest conversion rate, also the GetADC always takes a dummy sample, thus needs two times a sampling cycle.

And btw., your problem whatsoever is in no way more important than others. Coloring the code in red instead of using proper code tags doesn't show most clever behavior.

dabatek · Joined: 31 Jul 2013 Posts: 32 Location: Serbia

Thank you MWS for clear and quick answer,
also is clear for coloring code...