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<H1><A NAME="SECTION00520000000000000000">
Writing Modules for the Embedded System (Creating I/O Drivers)</A>
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<P>
There are two reasons why you would need to even consider looking at
this section.
<P>
<OL>
<LI>You need to tune the performance of your I/O board such as
setting up the I/O base address, or the gain values for each of the
boards and would like to understand the structure of the I/O driver.
<P>
</LI>
<LI>None of the existent I/O drivers work on your specific I/O
hardware.
<P>
</LI>
</OL>
<P>
Whichever case applies to you, it turns out that writing a device
driver for either RTiC-Lab or RTLinux in general is quite a simple
process.
<P>
All of the files associated with the I/O boards are located under the
directories:
<P>
<UL>
<LI><TT>rtic_*.*.*/rt_tasks/ad_cards</TT>: drivers for A/D boards
<P>
</LI>
<LI><TT>rtic_*.*.*/rt_tasks/da_cards</TT>: drivers for D/A boards
</LI>
</UL>
<P>
The API that the device writer must use, however, is slightly
different that one would be normally used to. The following describes
the API as declared in RTiC-Lab. Generally speaking, the API described
below has the exact same functionality as its Linux-specific lowercase
counterpart. However, the difference is that whenever the user defines
the <TT>noIO</TT> token in the user's <TT>user_GUI.par</TT>, then all I/O
will be blocked. This is especially useful for controller logic
debugging purposes.
<P>
The basic API is defined as follows:
<P>
<UL>
<LI><TT>INW(x)</TT>
</LI>
<LI><TT>INB(x)</TT>
</LI>
<LI><TT>OUTB(x,y)</TT>
</LI>
<LI><TT>OUTW(x,y)</TT>
</LI>
</UL>
<P>
If you create any new device drivers or enhance any of the existing
ones, then you are encouraged to submit it to
<A NAME="tex2html43"
HREF="mailto:efhilton@fsmlabs.com"><TT>efhilton@fsmlabs.com</TT></A>
for
inclusion in future revisions of RTiC-Lab.
<P>
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<LI><A NAME="tex2html683"
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<LI><A NAME="tex2html684"
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<ADDRESS>
Michael Barabanov
2001-06-19
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