Ping360: Fetching the distance for a given angle

ping.py

from sensor import Ping360

# Global Variables
device = "/dev/ttyUSB0" # the serial port
baudrate = 115200
gain = 0
numberOfSamples = 200 # Number of points
transmitFrequency =  740 # Default frequency
sonarRange = 1 # in m
speedOfSound = 1500 # in m/s

# The function definitions are at the bottom
samplePeriod = calculateSamplePeriod(sonarRange, numberOfSamples, speedOfSound)
transmitDuration = adjustTransmitDuration(sonarRange, samplePeriod, speedOfSound)

# Initialize sensor
sensor = Ping360(device, baudrate)
print("Initialized Sensor: %s" % sensor.initialize())

# Set sonar parameters
sensor.set_gain_setting(gain)
sensor.set_transmit_frequency(transmitFrequency)
sensor.set_transmit_duration(transmitDuration)
sensor.set_sample_period(samplePeriod)
sensor.set_number_of_samples(numberOfSamples)

 # Get sonar response
angle = 0 # in Grad
data = getSonarData(sensor, angle) # A list of intensities from (0 - 255) for the given angle
# To get the distance, just set a threshold, let's say 150, and get the index of the list value that is superior to that threshold
# The index+1 represents the number of samples which then can be used to deduce the range

# for detectedIntensity in data:
#     if detectedIntensity >= threshold:
#         detectedIndex = data.index(detectedIntensity)
#         break
distance = calculateRange((1 + detectedIndex), samplePeriod, speedOfSound)

def calculateRange(numberOfSamples, samplePeriod, speedOfSound, _samplePeriodTickDuration=25e-9):
    # type: (float, int, float, float) -> float
    """
      Calculate the range based in the duration
     """
    return numberOfSamples * speedOfSound * _samplePeriodTickDuration * samplePeriod / 2

def getSonarData(sensor, angle):
    """
    Transmits the sonar angle and returns the sonar intensities
    Args:
        sensor (Ping360): Sensor class
        angle (int): Gradian Angle
    Returns:
        list: Intensities from 0 - 255
    """
    sensor.transmitAngle(angle)
    data = bytearray(getattr(sensor, '_data'))
    return [k for k in data]
  
def calculateRange(numberOfSamples, samplePeriod, speedOfSound, _samplePeriodTickDuration=25e-9):
    # type: (float, int, float, float) -> float
    """
      Calculate the range based in the duration
     """
    return numberOfSamples * speedOfSound * _samplePeriodTickDuration * samplePeriod / 2


def calculateSamplePeriod(distance, numberOfSamples, speedOfSound, _samplePeriodTickDuration=25e-9):
    # type: (float, int, int, float) -> float
    """
      Calculate the sample period based in the new range
     """
    return 2 * distance / (numberOfSamples * speedOfSound * _samplePeriodTickDuration)


def adjustTransmitDuration(distance, samplePeriod, speedOfSound, _firmwareMinTransmitDuration=5):
    # type: (float, float, int, int) -> float
    """
     @brief Adjust the transmit duration for a specific range
     Per firmware engineer:
     1. Starting point is TxPulse in usec = ((one-way range in metres) * 8000) / (Velocity of sound in metres
     per second)
     2. Then check that TxPulse is wide enough for currently selected sample interval in usec, i.e.,
          if TxPulse < (2.5 * sample interval) then TxPulse = (2.5 * sample interval)
        (transmit duration is microseconds, samplePeriod() is nanoseconds)
     3. Perform limit checking
     Returns:
        float: Transmit duration
     """
    duration = 8000 * distance / speedOfSound
    transmit_duration = max(
        2.5 * getSamplePeriod(samplePeriod) / 1000, duration)
    return max(_firmwareMinTransmitDuration, min(transmitDurationMax(samplePeriod), transmit_duration))


def transmitDurationMax(samplePeriod, _firmwareMaxTransmitDuration=500):
    # type: (float, int) -> float
    """
    @brief The maximum transmit duration that will be applied is limited internally by the
    firmware to prevent damage to the hardware
    The maximum transmit duration is equal to 64 * the sample period in microseconds
    Returns:
        float: The maximum transmit duration possible
    """
    return min(_firmwareMaxTransmitDuration, getSamplePeriod(samplePeriod) * 64e6)


def getSamplePeriod(samplePeriod, _samplePeriodTickDuration=25e-9):
    # type: (float, float) -> float
    """  Sample period in ns """
    return samplePeriod * _samplePeriodTickDuration