Usar PC como frequencímetro??
Enviado: 07 Abr 2007 21:00Encontrei na net um texto o qual tentei traduzir mas ficou um pouco confuso.(meu ingreis é bad...)
Pelo que eu entendi é posivel usar o PC como frequencimetro pela porta paralela ( eu já vi usando placa de som mas.. ) e tal.
Bem vou postar o texto e o link para ficar mais "claro" a todos>
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"A simple, low cost, and precision frequency meter uses only two pins of a pc parallel port (Figure 1). The TTL-level periodic input signal with frequency fIN connects to the ACK pin of LPT1. This input produces an IRQ7 hardware in- terrupt on every rising edge (Figure 2). The software counts the number of IRQ7 interrupts in the time unit of timebase T. If this timebase is 1 sec, the frequency of the input signal equals the number of IRQ7 interrupts in 1 sec.
You can use many ways to precisely generate the timebase, T, such as using the delay() or sleep() functions in C. You can also use software calibration loops. Unfortunately, these techniques are unreliable because they are based on polling. The best choice is to use a second interrupt, such as IRQ0 (software 0x1C). This interrupt is related to the internal PC timer and occurs 18.2 times/sec. For precise measurements, you can use proportional constants. For example, if your timebase equals the 18 IRQ0, you must correct the result by a factor of 18.2/18.
The software in Listing 1 is simple and interrupt-based, which allows for resident operation in an MS-DOS environment and for multitasking mode under Windows. For a timebase of 1 sec and using a 100-MHz Pentium PC, the frequency meter gives good results in the range of 10 Hz to 10 kHz with errors less than 0.26% for DOS and 0.94% for Windows (Figure 3). This design uses a Tektronix (www.tek.com) CFG280 function generator for reference. A faster PC should produce even better results.
Listing 1 is written in Borland C++ compiler, and you can use the same program for DOS-based C compilers, such as Turbo C. Also, you can use the second parallel port LPT2, with interrupt IRQ5, to perform this same frequency-meter function. If you add one voltage-to-frequency, current-to-frequency, or temperature- to-frequency converter, the frequency meter can also perform simple, low-cost, and high-resolution measurements of analog values. (DI #2342)"
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O link da página é esse:
http://www.edn.com/contents/images/42999di.pdf
O que vcs acham???
Té mais...
Pelo que eu entendi é posivel usar o PC como frequencimetro pela porta paralela ( eu já vi usando placa de som mas.. ) e tal.
Bem vou postar o texto e o link para ficar mais "claro" a todos>
............................................................
"A simple, low cost, and precision frequency meter uses only two pins of a pc parallel port (Figure 1). The TTL-level periodic input signal with frequency fIN connects to the ACK pin of LPT1. This input produces an IRQ7 hardware in- terrupt on every rising edge (Figure 2). The software counts the number of IRQ7 interrupts in the time unit of timebase T. If this timebase is 1 sec, the frequency of the input signal equals the number of IRQ7 interrupts in 1 sec.
You can use many ways to precisely generate the timebase, T, such as using the delay() or sleep() functions in C. You can also use software calibration loops. Unfortunately, these techniques are unreliable because they are based on polling. The best choice is to use a second interrupt, such as IRQ0 (software 0x1C). This interrupt is related to the internal PC timer and occurs 18.2 times/sec. For precise measurements, you can use proportional constants. For example, if your timebase equals the 18 IRQ0, you must correct the result by a factor of 18.2/18.
The software in Listing 1 is simple and interrupt-based, which allows for resident operation in an MS-DOS environment and for multitasking mode under Windows. For a timebase of 1 sec and using a 100-MHz Pentium PC, the frequency meter gives good results in the range of 10 Hz to 10 kHz with errors less than 0.26% for DOS and 0.94% for Windows (Figure 3). This design uses a Tektronix (www.tek.com) CFG280 function generator for reference. A faster PC should produce even better results.
Listing 1 is written in Borland C++ compiler, and you can use the same program for DOS-based C compilers, such as Turbo C. Also, you can use the second parallel port LPT2, with interrupt IRQ5, to perform this same frequency-meter function. If you add one voltage-to-frequency, current-to-frequency, or temperature- to-frequency converter, the frequency meter can also perform simple, low-cost, and high-resolution measurements of analog values. (DI #2342)"
................................................................................
O link da página é esse:
http://www.edn.com/contents/images/42999di.pdf
O que vcs acham???
Té mais...