Circle and Square

Last night I assembled the Quick2Wire analogue board. The software setup took a little bit of fiddling, after which I was able to make the simple tests described at Quick2Wire and a measurement with a potentiometer. The source I found most useful was the post at www.miraculum.ch.

1. Set up ictools as described at adafruit.

2. Install the quick2wire-python-api in a directory /home/git as Miraculum recommends. (Make this directory if need be).

   $ cd git
   $ git clone https://github.com/quick2wire/quick2wire-python-api.git

3. Find the file pcf8591read:

   $ find /home /usr -name pcf8591read 

Make a copy of this file in ~/git and rename it as pcf8591read.py. Then add the line indicated below to the code so that the head of the file looks like this:

   #! /usr/bin/env python3

   import sys
   sys.path.append(r'/home/pi/git/quick2wire-python-api/')  # add this
   from quick2wire.i2c import I2CMaster                     
   from quick2wire.parts.pcf8591 import *                   

As noted in Miraculum’s post, the added line ensures that the program finds the needed parts of the quick2wire-python-api.

4. On the Quick2Wire Analogue board, run a jumper from AIN0 to GND. Then say sudo python3 pcf8591read.py. You should see this:

pi@raspberrypi ~/git $ sudo python3 pcf8591read.py 
read: 1 : 0.0
read: 2 : 0.0
read: 3 : 0.0

5. Now run the jumper from AIN0 to VREF. You should see this:

pi@raspberrypi ~/git $ sudo python3 pcf8591read.py 
read: 1 : 1.0
read: 2 : 1.0
read: 3 : 1.0

6. Attach a potentiometer as follows: one outside lead to GND, the other to VREF, the middle lead to AIN0. Then test. You will get something like this as you rotate the potentiometer:

pi@raspberrypi ~/git $ sudo python3 pcf8591read.py 
read: 1 : 0.0
read: 2 : 0.0
read: 3 : 0.0
read: 4 : 0.06274509803921569
read: 5 : 0.14901960784313725
read: 6 : 0.20392156862745098
read: 7 : 0.2627450980392157
read: 8 : 0.3254901960784314
read: 9 : 0.39215686274509803
read: 10 : 0.47058823529411764
read: 11 : 0.5686274509803921
read: 12 : 0.6705882352941176
read: 13 : 0.796078431372549
read: 14 : 0.9686274509803922
read: 15 : 1.0
read: 16 : 1.0

RPi with Quick2Wire interface and analogue boads