Close ticket 1131

David dpnsw at
Wed Feb 12 23:33:00 CET 2003


I have raised a ticket about not being able to find how to get the i2c-pcf-epp 
module. Ticket number 1131. This can be closed as I now know where it is and 
why it is this way. 

Maybe you could consider adding a bit of text on the page
under the single paragraph of explanation for the diagram.

I offer the following for comments, suggestions and corrections. It is 
something that I feel would have helped me a great deal as I sought to 
understand the lm_sensors project and would have also avoided me raising 2 
support requests.

So here goes::

The program rectangle is made up of the lm_sensors userspace programs and 
configuration and documentation files.
Examples of which are:
and associated man pages 

As you can see from the diagram this is only a small part of a working 
lm_sensors installation. The rest of the work is done inside the kernel by 
two branches of lm_sensors that work together, one is called sensors (or 
should that be sensors2) while the other is i2c. You will need both in order 
to fully utilise lm_sensors. Depending on what kernel you are using (or more 
specifically what kernel your distribution has provided to you) will 
determine what lm_sensors is capable of doing. If you find that you cannot 
address all of the sensor chips you have or maybe you can't even get 
i2cdetect to see your adaptor chip then you should check to see if lm_sensors 
supports your hardware on  

If your hardware is supported but your current kernel/distribution isn't 
working then you will probably have to patch and compile the kernel.

You could just download the latest kernel version from or get 
the sources from your distribution. If you do this and compile it, being 
carefull to configure all the devices you need, you should be aware that even 
the latest kernel from does not have all of the supported sensors 
and chips in it. To enable a kernel from to support all of the 
sensors, algorithms and adaptors that it is capable of you will need to patch 
the kernel. Patches are available from for the 
later 2.4 series kernels. 

You can apply patches by:
cd path_to_your_kernel_sources
path -p1 -E < path_to_the_patches/2.4.20-sensors-1-patch

Do the same for all the sensors and i2c patches you downloaded.
Note: As patches are prepared against kernels from if you are 
patching against your distribution specific source code there is a 
possibility that the patches won't cleanly apply. If this is the case you can 
either try and resolve it manually (if you are capable of doing this), get a 
kernel from or give up and go and do something else.

Detailed information about compiling & patching the kernel is available at

A note about algorithm and adaptor code:
Most code for algorithm and adaptors are combined into the one module as you 
need both in order to be able to function correctly. There are a couple of 
exceptions to this in the form of parallel port adaptors.

Parallel port adaptors
Most people don't need to worry about this.
If you are installing parallel port adaptors it means you are probably messing 
around with wires and IC's and the like. If you have purchased a card that 
provides external an external i2c/smbus this will have combined algorithm and 
adaptor code. If you are doing it yourself by using the parallel port there 
are basically 2 options.

1) Using the parallel port and using the i2c-pport adaptor module and the 
i2c-algo-bit algorithm module together to enable you to wire up your parallel 
port to act as an i2c/smbus. This provides a bus that will enable most 
sensors to work but doesn't support the entire i2c/smbus capability

2) Using the parallel port to interface to a Philips PCF8584 parallel to i2c 
adaptor chip. You will need to build a bit of a circuit to do this. This 
configuration needs the i2c-pcf-epp adaptor module and the i2c-algo-pcf 
algorithm module. This support almost all of the i2c/smbus capabilities

Okay that's it. Did I get it mostly right?

Turned out a bit longer than I expected. Feel free to use, change or omit as 
you feel appropriate.

Many thanks for all your efforts and the project. It is really great (be even 
better when I get it working ;)

Best Regards,

David Price

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