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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.
Values below correspond
with 170 m/s. every step takes one value from adc_array and
store adc_value local variable.
At first program clear max and put min high value. first is
defined variable.4.4.4. Than actual adc_value tested higher than max
28
. Then tested flag set X_PWM Y_PWM state.
After that get value from timer and calculate measured time as
a complement timer_load_set.9 ADC peak peak function
The adc_peaktopeak function called after gpio_post_int from main function. There are local variable on
the beginning.
Illustration 4.8 GPIO post interrupt function
The gpio_post_int function called from main after adc_sample function.
The function has adc_array address input argument. 12500 clock cycles, timer has lower value than 15000, digital
input interrupt could happened because received noise some reflected signal. flag fulfill
this condition, program exit from function. In
that case set flag for next measurement. were discounting from 31250 (2,5 ms) and signal
takes 1,5 spread between sensor, has measure 18750. Actually this value
can from 2500 5000 higher because another details. Then tested flag parameter let know, which PWM generator
has switch off. Program returns measured time and exit. There are some correction
of this error later.11: Flowchart GPIO post interrupt function
4. Digital input interrupt pin level disabled and flag set next
state, X_WIND_CALC Y_WIND_CALC.
At the end test value correct range. It
calculate difference between maximum and minimum sampled sequence. we
multiply this number 3,3 and divided 1000, had peak peak voltage of
received signal. This can happen for too low measured time. sampled 128 values,
program stay loop for 128 cycles
