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Kategorie: Diplomové, bakalářské práce |
Tento dokument chci!
Práce popisuje principy a problémy při realizaci ultrazvukového anemometru. Je popsán princip výpočtu rychlosti větru a následné korekce výpočtu. Pro realizaci jsou využity ultrazvukové sensory a microcontrolér ARM Cortex-M3. Práce se zabývá generováním PWM signálu, jeho analogovou filtrací, zesílením a odvysíláním. Na přijímací straně jeto nízkonapěťový zesilovač a komparátor. Vyvíjený kód je popsán pomocí vývojového diagramu.
9 ADC peak peak function
The adc_peaktopeak function called after gpio_post_int from main function.
At first program clear max and put min high value. 12500 clock cycles, timer has lower value than 15000, digital
input interrupt could happened because received noise some reflected signal. sampled 128 values,
program stay loop for 128 cycles. we
multiply this number 3,3 and divided 1000, had peak peak voltage of
received signal.4. every step takes one value from adc_array and
store adc_value local variable. This can happen for too low measured time.
The function has adc_array address input argument. flag fulfill
this condition, program exit from function. Than actual adc_value tested higher than max
28
.4.8 GPIO post interrupt function
The gpio_post_int function called from main after adc_sample function. Values below correspond
with 170 m/s. Actually this value
can from 2500 5000 higher because another details. Then tested flag parameter let know, which PWM generator
has switch off. were discounting from 31250 (2,5 ms) and signal
takes 1,5 spread between sensor, has measure 18750. There are local variable on
the beginning. Digital input interrupt pin level disabled and flag set next
state, X_WIND_CALC Y_WIND_CALC.4.
At the end test value correct range.11: Flowchart GPIO post interrupt function
4.
After that get value from timer and calculate measured time as
a complement timer_load_set. In
that case set flag for next measurement. There are some correction
of this error later.
Illustration 4. Program returns measured time and exit. Then tested flag set X_PWM Y_PWM state. first is
defined variable. It
calculate difference between maximum and minimum sampled sequence
