Thank John for Sharing and Python MAX SONAR

On 7/13/15 John Bohlhuis contribute his own Python code that he is using to automate the reading of distance values.
We gladly share this for your use in your projects.
Thank you John for sharing.


***************************************************************************
First, the Python module that does the actual work:
***************************************************************************

#!/usr/bin/python3
# Filename: maxSonarTTY.py

# Reads serial data from Maxbotix ultrasonic rangefinders
# Gracefully handles most common serial data glitches
# Use as an importable module with "import MaxSonarTTY"
# Returns an integer value representing distance to target in millimeters

from time import time
from serial import Serial

serialDevice = "/dev/ttyAMA0" # default for RaspberryPi
maxwait = 3 # seconds to try for a good reading before quitting

def measure(portName):
    ser = Serial(portName, 9600, 8, 'N', 1, timeout=1)
    timeStart = time()
    valueCount = 0

    while time() < timeStart + maxwait:
        if ser.inWaiting():
            bytesToRead = ser.inWaiting()
            valueCount += 1
            if valueCount < 2: # 1st reading may be partial number; throw it out
                continue
            testData = ser.read(bytesToRead)
            if not testData.startswith(b'R'):
                # data received did not start with R
                continue
            try:
                sensorData = testData.decode('utf-8').lstrip('R')
            except UnicodeDecodeError:
                # data received could not be decoded properly
                continue
            try:
                mm = int(sensorData)
            except ValueError:
                # value is not a number
                continue
            ser.close()
            return(mm)

    ser.close()
    raise RuntimeError("Expected serial data not received")

if __name__ == '__main__':
    measurement = measure(serialDevice)
    print("distance =",measurement)




***************************************************************************
Also, here is a sample Python script that shows how the module may be used:
***************************************************************************


#!/usr/bin/python3
# Filename: rangeFind.py

# sample script to read range values from Maxbotix ultrasonic rangefinder

from time import sleep
import maxSonarTTY

serialPort = "/dev/ttyAMA0"
maxRange = 5000  # change for 5m vs 10m sensor
sleepTime = 5
minMM = 9999
maxMM = 0

while True:
    mm = maxSonarTTY.measure(serialPort)
    if mm >= maxRange:
        print("no target")
        sleep(sleepTime)
        continue
    if mm < minMM:
        minMM = mm
    if mm > maxMM:
        maxMM = mm

    print("distance:", mm, "  min:", minMM, "max:", maxMM)
    sleep(sleepTime)