Help with code to access USB port

[donmerch]

So I have 2 different Maxbotix USB sensors connected to a USB hub. They enumerate as /dev/ttyUSB0 and /dev/ttyUSB1. I'm trying to cycle through both sensors using this code:

#!/usr/bin/python3
# sample script to read range values from Maxbotix ultrasonic rangefinder

from time import sleep
import maxSonarTTY

serialPort  = "dev/ttyUSB"
maxRange = 5000  # change for 5m vs 10m sensor
sleepTime = 1
minMM = 9999
maxMM = 0
port  = 0

while port <= 1:
    mm = maxSonarTTY.measure(serialPort + str(port))
    print(str(port) + " Value: ", mm)
    port = port + 1
    sleep(sleepTime)

I get this error:

Traceback (most recent call last):
  File "/home/pi/Documents/Python Projects/PyMaxBotix-master/rangeBox2.py", line 21, in <module>
    mm = maxSonarTTY.measure(serialPort1)
NameError: name 'serialPort1' is not defined

If I try this:

#!/usr/bin/python3
# sample script to read range values from Maxbotix ultrasonic rangefinder

from time import sleep
import maxSonarTTY

serialPort  = "dev/ttyUSB"
maxRange = 5000  # change for 5m vs 10m sensor
sleepTime = 1
minMM = 9999
maxMM = 0
port  = 0

while port <= 1:
    print(serialPort + str(port))
    port = port + 1
    sleep(sleepTime)

I get this which appears to work:

>>> ================================ RESTART ================================
>>> 
dev/ttyUSB0
dev/ttyUSB1
>>> 

---

If I manually put in /dev/ttyUSB0 and /dev/ttyUSB1 then it works but I'm trying to cycle through several ports. I plan to add up to 6 sensors through the USB ports.

[Larz60+]

You may want to take a look at this package: https://pypi.python.org/pypi/libusb1/1.6.4
Even if you don't use it, you may get some ideas from looking at the code.

[Ofnuts]

I don't understand how this:

serialPort  = "dev/ttyUSB"
port  = 0
 
while port <= 1:
    mm = maxSonarTTY.measure(serialPort + str(port))

Can make your code reference a variable named serialPort1 (and I understand even less why in that case it doesn't complain first about serialPort0). Is there a serialPort1 variable hiding somewhere?