www.micro-examples.com

[BrunoG]

The P16F84A simple frequency meter is ready !

It will be discussed here.
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BrunoG, Administrator

[hugo]

Hi,

For a 16 MHz crystal we have:

while(ovrflw < 15626) ; //15625 = 16 000 000 / 4 * 256

what will be the right value for a 20MHz crystal:

while(ovrflw < 19532) ; //19531.25 = 20 000 000 /4*256

Thanks

[BrunoG]

Hi Hugo,

I would better use 19531 which is closer to computed value 19531.25.

By the way, the accuracy should not differ that much between the two values !

Thanks,
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BrunoG, Administrator

[yylee]

Why the 256 have to multiply by 4? Where does the '4' come from? Thank.
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Look ever forward

[BrunoG]

[yylee]

Thanks! Any suggestion where I can find more info about the theory behind the microcontroller? Thank.
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Look ever forward

[BrunoG]

Hi,

I suggest you to read the very good book of Nebojsa Matic "PIC Microcontrollers" :

http://www.mikroe.com/en/books/picbook/picbook.htm

It is on-line, and it is free !
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BrunoG, Administrator

[Ford]

Hehe, I'm sorry but i must write punchline
Literal translation of the name "Nebojsa" is "dreadnought", meaning someone, who is not afraid (anything, anywhere, against nothing).

[BrunoG]

So "Nebojsa Matic" is the one who is not afraid of autoMatic process ?

If he can read this, maybe he will give the answer
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BrunoG, Administrator

[Clonus]

This example is just what I've been looking for, however, I am having a helluva time getting the output to be correct.

I am using a 16f84a at 20mhz, with the minor mod listed above.

I get nothing but garbage from the serial output.

Is there a modification for this?

It would be nice to have a working piece of code.

thanks!

[BrunoG]

Hello,

I tried to build the project with the source code from the web page example, and I noticed that the soft UART init function prototype has changed since last mikroC revision, please use now :

[Clonus]

oh yes, sorry, soft_uart_init did change as well. glad you noticed.

besides this, I still get garbage at both higher and lower baud rates. If I compile even a simple "hello world" application I still get garbage.

I tried with MikroC < never works

PicBasic < works just fine.

Also, after all my troubles I noticed that PicBasic has a "Count" command to test frequency on a port. Have you ever tried comparing the results?

Just trying to save myself a hundred bucks by building something simple.

thanks
clonus

[BrunoG]

You still get garbage ?
It should workd at first try with a 1200-8-N-1 serial communication line

I tested my PIC16F84A serial output frequency meter with a function generator and it is ok for the range I mention, but I don't know what you can expect from the picbasic count routine
you can try to wake up this thread :
http://www.micro-examples.com/forums/viewtopic.php?t=106
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BrunoG, Administrator

[Clonus]

1200 is too low a baud rate at 20mhz, so i tried 2400, still no luck [/img]

[BrunoG]

Can you please send me you full mikroC folder of this project by email ?
I will check on my hardware
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BrunoG, Administrator