Kart/sensors/HCSR04
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Ultrasound ranger
The elecfreaks
Ultrasonic sensor distance measuring module
receives a trigger pulse, startMeasure
, sends an ultrasonic pulse train
and then provides a pulse, distancePulse
, whose length is proportional to the sound flight and echo time.
It has a dedicated connector on the I/O board.
The ultrasoundRanger
block in the sensors
FPGA counts the ultrasonic pulse length in terms of the 10 MHz clock periods.
The distance is thus given by:
There is approximately 500 us between the trigger and the start of the answer. Moreover, for ranges of about 20-30 cm, the return signal duration is of an order of 2 ms. Thus, going above 10 ms (100Hz) for the whole measure is not a good idea.