Analyzing waveforms in Microcontrollers

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djalli

Joined: 10 Nov 2001
Posts: 887
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Location: 1600 Pennsylvania Avenue, Washington DC 20500

28 Nov 2003 20:50 Analyzing waveforms in Microcontrollers

I have 0 experience in Microcontrollers. If I turn on my function generator and send a 100Hz, 5volts p-p CAN I analyze this waveform. Such as getting frequency, amplitude etc. using a microcontroller?

If possible point me to links where people have played, experimented with analog waveforms.

bobcat1

Joined: 10 Jul 2002
Posts: 1118
Helped: 48

29 Nov 2003 12:12 Re: Analyzing waveforms in Microcontrollers

The answer is YES but it depend on the type of the controller used

If you need a controller to analyze signals it not the best soulation because to analyze signals (FFT for instance it's best to use a DSP chip )

But to day's you can use a low cost micro a one i can recomend is the 8051f23x

it's can work up to 20 mips (milyon instrucation per second)

and you can use it to analyze a signal using FFT or you can use the new motorola dsp f830 serias it's a combination of DSp and a micro controller

best

bobi

cancel

Joined: 27 May 2001
Posts: 286
Helped: 11

29 Nov 2003 12:26

hi .. you can find a lot of examples searching e.g. google ;0)
one of them : http://home.iprimus.com.au/wjmoore/pic/proj_spec2.html
depends on what you need .. e.g. avr can do up to 16mips, cygnal up to 100 mips ..

techie

Joined: 05 Feb 2002
Posts: 850
Helped: 43
Location: Pakistan

29 Nov 2003 17:18

Micros are good at measuring low frequencies and can also be used to measure amplitude using an onboard or external ADC. What you require can be done but dont expect to get up and start doing it right away. As you said that you have no experience in using micros. So you need to learn to use them hardware and software wise. Start with simple applications before going on to difficult ones. Better get some starter kit and get going some LEDs and switches stuff before experimenting frequencies and waveforms.

djalli

Joined: 10 Nov 2001
Posts: 887
Helped: 15
Location: 1600 Pennsylvania Avenue, Washington DC 20500

30 Nov 2003 4:12

techie wrote:

To all of you thank you. Yes it is true and it has been a great desire with me to work with microcontroller and as bobcat1 mentioned DSP chip are far better to do FFT.

I do not know where to start. Is any simulation package software? I know MPLAB should be one.

It is a long journey to learn these but it is best. Matlab has some toolkit for DSP chips? Is that relevant?

Anyhow many thanks!

sokrat

Joined: 23 Sep 2002
Posts: 371
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Location: EGYPT

30 Nov 2003 8:47 Re: Analyzing waveforms in Microcontrollers

djalli wrote:

Dear

I was detect dtmf signal using pic 16 f877 using FFT but first you must know what you want to from signal ... and what kind of signal you will receive sine square ..Etc
1- if signal square you can measure frequency direct from microcontroller
By using timer as external counter "assume you frequency is low frequency " if the frequency is high you can use external divider IC
2-if signal not square you can clip the peak and then measure the frequency
3- measure amplitude you can use ADC
NOTE:
if the signal is complex signal then you can use FFT
S Shocked

KRAT

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djalli

Joined: 10 Nov 2001
Posts: 887
Helped: 15
Location: 1600 Pennsylvania Avenue, Washington DC 20500

30 Nov 2003 10:44 Re: Analyzing waveforms in Microcontrollers

sokrat wrote:

Dear sokrat

What I want from a signal is frequency since it is important and as you mentioned amplitude I can use ADC.
I will analyze some complex signal some day let say: a random sinewave where first 10sec is 100Hz and the next 3seconds is 1Khz etc so on.

Never thought of using square waves. Good ide to experiment with. Thank you sokrat.

sokrat

Joined: 23 Sep 2002
Posts: 371
Helped: 2
Location: EGYPT

30 Nov 2003 12:44 Re: Analyzing waveforms in Microcontrollers

ok ....

about frequency you can measure it using microcontroller but first you must convert this sin wave to square wave and then measure frequency using microcontroller but remember the frequency for input signal must not greater than the oscillator clock for microcontroller

S Shocked

KRAT

Aoxomox

Joined: 18 Jul 2001
Posts: 90

30 Nov 2003 14:17 Re: Analyzing waveforms in Microcontrollers

If you want to decode a FSK modulated signal you can use some analog prefilters that each detects one of the frequencies and the µC will only test which prefilter receives something.

Maybe you should describe what kind of signal you really want to work with and what is interesting for you.
The data acquisition path must be clear first to determin if it can be done with a µC, a DSP, or simple analog/digital hardware.
(24bit audio/video processing needs powerfull DSP, reading out a PWM coded signal from a temperature sensor can be done in very slow runing µC)

Additionally a µC has some features (PWM/Timers/interrupt inputs...) that if used in a wise way can allow the implementation of a high speed problem, that normally requires a DSP. In such cases it is even more important to exactly know the goal of your measurement application to decide what will be done in hard- and what in software.

I would suggest starting off with a program like LabView first to get some experience with the data acquisition and then, if it runs stable, port it to your µC. In LabView you can first generate some example signals and test your structure with real world signals better than you can do this in a µC without any debug possibilties.

Hope it helps

aOxOmOx

djalli

Joined: 10 Nov 2001
Posts: 887
Helped: 15
Location: 1600 Pennsylvania Avenue, Washington DC 20500

03 Dec 2003 22:09 Re: Analyzing waveforms in Microcontrollers

Aoxomox thank you, I see what you hint.

Can I export LabView vi to a C code or anything else to I can port in uC?
I may like to experiment with DSP chips.
What is, is a real signal and I want to measure various frequencies. If the signal is human heartbeat, pre-recorded data, I must detect missing pulse so I know that heartbeat did not go in normal range. If heart stops that would be no signal which is easy to detect at least in Matlab.

thanks again.