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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.
Illustration 4. This can happen for too low measured time.
At the end test value correct range. sampled 128 values,
program stay loop for 128 cycles.
At first program clear max and put min high value. There are local variable on
the beginning.
The function has adc_array address input argument. we
multiply this number 3,3 and divided 1000, had peak peak voltage of
received signal. flag fulfill
this condition, program exit from function. first is
defined variable.11: Flowchart GPIO post interrupt function
4. were discounting from 31250 (2,5 ms) and signal
takes 1,5 spread between sensor, has measure 18750. Digital input interrupt pin level disabled and flag set next
state, X_WIND_CALC Y_WIND_CALC.9 ADC peak peak function
The adc_peaktopeak function called after gpio_post_int from main function. Actually this value
can from 2500 5000 higher because another details. every step takes one value from adc_array and
store adc_value local variable.4. Then tested flag parameter let know, which PWM generator
has switch off.
After that get value from timer and calculate measured time as
a complement timer_load_set.4. In
that case set flag for next measurement. It
calculate difference between maximum and minimum sampled sequence. There are some correction
of this error later. Values below correspond
with 170 m/s. Then tested flag set X_PWM Y_PWM state. 12500 clock cycles, timer has lower value than 15000, digital
input interrupt could happened because received noise some reflected signal. Program returns measured time and exit. Than actual adc_value tested higher than max
28
.8 GPIO post interrupt function
The gpio_post_int function called from main after adc_sample function.4
