RPi ADC I2C Python - Revision history

Bgirardot: Changed PYTHONPATH to point to root of the directory instead of src/ directory - See discussion page for reason

2013-01-15T00:44:10Z

Changed PYTHONPATH to point to root of the directory instead of src/ directory - See discussion page for reason

AndrewS: updated distro note

2012-12-06T04:09:47Z

updated distro note

AndrewS: /* Reading ADC values over I2C using Python */

2012-09-24T14:04:53Z

‎Reading ADC values over I2C using Python

AndrewS: Added links back to Tutorials page

2012-09-24T13:57:36Z

Added links back to Tutorials page

AndrewS: Created page with "== Reading ADC values over I2C using Python == I (AndrewS) recently bought a [http://www.abelectronics.co.uk/products/3/Raspberry-Pi/7/ADC-Pi---Raspberry-Pi-Ana..."

2012-09-23T22:16:22Z

Created page with "== Reading ADC values over I2C using Python == I (AndrewS) recently bought a [http://www.abelectronics.co.uk/products/3/Raspberry-Pi/7/ADC-Pi---Raspberry-Pi-Ana..."

New page

== Reading ADC values over I2C using Python ==

I ([[User:AndrewS|AndrewS]]) recently bought a [http://www.abelectronics.co.uk/products/3/Raspberry-Pi/7/ADC-Pi---Raspberry-Pi-Analogue-to-Digital-converter ADC Pi] RaspberryPi addon board from http://www.abelectronics.co.uk/ - there were a few tricky points in getting it working, so I thought I'd write this step-by-step tutorial. The instructions below are all based on the [http://www.raspberrypi.org/downloads 2012-09-18-wheezy-raspbian distro] but should be equally applicable to other distros.

=== Instructions ===
Files in the ''/etc'' directory below need to be edited as root, so use '''sudo nano ''filename'' '''

# Enable I2C support
#* add '''i2c-dev''' to the end of ''/etc/modules''
#* comment out (with a '''#''') the line that says '''blacklist i2c-bcm2708''' in ''/etc/modprobe.d/raspi-blacklist.conf''
# Enable the pi user to access I2C hardware
#* install i2c-tools (includes ''i2cdetect'' and adds the ''i2c'' group) with: '''sudo apt-get update && sudo apt-get install i2c-tools'''
#* add the ''pi'' user to the ''i2c'' group with: '''sudo adduser $USER i2c'''
# Install the Quick2Wire Python API
#* install ''git'' with: '''sudo apt-get install git'''
#* download the API with: '''git clone https://github.com/quick2wire/quick2wire-python-api.git'''
#* enable Python to access the API by adding '''export PYTHONPATH=$PYTHONPATH:$HOME/quick2wire-python-api/src''' to the end of ''/home/pi/.profile''
# Reboot to enable all the above changes
#* '''sudo reboot'''
# Download and run the demo script
#* download it with: '''wget http://www.andrewscheller.co.uk/adc_demo.py'''
#* make it executable with: '''chmod +x adc_demo.py'''
#* run it with: '''./adc_demo.py'''

If everything went well you should now find that you get: 
''1: 0.000000'' 
''2: 0.000000'' 
''3: 0.000000'' 
''4: 0.000000'' 
''5: 0.000000'' 
''6: 0.000000'' 
''7: 0.000000'' 
''8: 0.000000'' 
printed repeatedly to the screen.
You can test that the ADC is working by using e.g. a bent paperclip to connect the "5V" on the board to one of the eight ADC channels, and the corresponding reading on screen should then read approximately 5V (in fact, the voltage output by your PSU).

@@ Line 5: / Line 5: @@
 I ([[User:AndrewS|AndrewS]]) recently bought a [http://www.abelectronics.co.uk/products/3/Raspberry-Pi/7/ADC-Pi---Raspberry-Pi-Analogue-to-Digital-converter ADC Pi] ('''A'''nalogue to '''D'''igital '''C'''onverter) RaspberryPi addon board from http://www.abelectronics.co.uk/ - there were a few tricky points in getting it working, so I thought I'd write this step-by-step tutorial. The instructions below are all based on the [http://www.raspberrypi.org/downloads 2012-09-18-wheezy-raspbian distro] but should be equally applicable to other distros.
 === Instructions ===
@@ Line 36: / Line 37: @@
 ''8: 0.000000''<br>
 printed repeatedly to the screen.
-You can test that the ADC is working by using e.g. a bent paperclip to connect the "5V" on the board to one of the eight ADC channels, and the corresponding reading on screen should then read approximately 5V (in fact, the voltage output by your PSU).
+You can test that the ADC is working by using e.g. a bent paperclip to connect the "5V" on the board to one of the eight ADC channels, and the corresponding reading on screen should then read approximately 5V (in fact, the voltage output by your PSU). Stop the script with the usual Ctrl+C.
 Back to the [[R-Pi Hub|Hub]], or the [[RPi Tutorials|Tutorials]] page.

@@ Line 19: / Line 19: @@
 #* install ''git'' with: '''sudo apt-get install git'''
 #* download the API with: '''git clone https://github.com/quick2wire/quick2wire-python-api.git'''
-#* enable Python to access the API by adding '''export PYTHONPATH=$PYTHONPATH:$HOME/quick2wire-python-api/src''' to the end of ''~/.profile''
+#* enable Python to access the API by adding '''export PYTHONPATH=$PYTHONPATH:$HOME/quick2wire-python-api''' to the end of ''~/.profile''
 # Reboot to enable all the above changes
 #* '''sudo reboot'''

@@ Line 4: / Line 4: @@
 == Reading ADC values over I2C using Python ==
-I ([[User:AndrewS|AndrewS]]) recently bought a [http://www.abelectronics.co.uk/products/3/Raspberry-Pi/7/ADC-Pi---Raspberry-Pi-Analogue-to-Digital-converter ADC Pi] RaspberryPi addon board from http://www.abelectronics.co.uk/ - there were a few tricky points in getting it working, so I thought I'd write this step-by-step tutorial. The instructions below are all based on the [http://www.raspberrypi.org/downloads 2012-09-18-wheezy-raspbian distro] but should be equally applicable to other distros.
+I ([[User:AndrewS|AndrewS]]) recently bought a [http://www.abelectronics.co.uk/products/3/Raspberry-Pi/7/ADC-Pi---Raspberry-Pi-Analogue-to-Digital-converter ADC Pi] ('''A'''nalogue to '''D'''igital '''C'''onverter) RaspberryPi addon board from http://www.abelectronics.co.uk/ - there were a few tricky points in getting it working, so I thought I'd write this step-by-step tutorial. The instructions below are all based on the [http://www.raspberrypi.org/downloads 2012-09-18-wheezy-raspbian distro] but should be equally applicable to other distros.
 === Instructions ===
@@ Line 12: / Line 12: @@
 #* add '''i2c-dev''' to the end of ''/etc/modules''
 #* comment out (with a '''#''') the line that says '''blacklist i2c-bcm2708''' in ''/etc/modprobe.d/raspi-blacklist.conf''
-# Enable the pi user to access I2C hardware
+# Enable the current user to access I2C hardware
 #* install i2c-tools (includes ''i2cdetect'' and adds the ''i2c'' group) with: '''sudo apt-get update && sudo apt-get install i2c-tools'''
-#* add the ''pi'' user to the ''i2c'' group with: '''sudo adduser $USER i2c'''
+#* add the current user to the ''i2c'' group with: '''sudo adduser $USER i2c'''
 # Install the Quick2Wire Python API
 #* install ''git'' with: '''sudo apt-get install git'''
 #* download the API with: '''git clone https://github.com/quick2wire/quick2wire-python-api.git'''
-#* enable Python to access the API by adding '''export PYTHONPATH=$PYTHONPATH:$HOME/quick2wire-python-api/src''' to the end of ''/home/pi/.profile''
+#* enable Python to access the API by adding '''export PYTHONPATH=$PYTHONPATH:$HOME/quick2wire-python-api/src''' to the end of ''~/.profile''
 # Reboot to enable all the above changes
 #* '''sudo reboot'''