Some years ago I wrote a keyboard driver using 2 parallel IO
bits. These were in a FPGA, logic allowed one line (KBCLK) to generate
interrupts when it changed states. I decoded Scan Code Set 2. I think
the PS/2 format is Scan Code Set 3, and it would be easier. This was
about 5 weeks of code, and required lots of tweaking with various
keyboards. Various keyboards do things a little different, ACK timeing,
Reset Functions were real problems. Newer keyboards (>1997) seemed
more consistent.
If you have specific question give me a shout. I suggest a small
FPGA to unload the ARM. There were a number of timing function that
were done in software. During some exception it took 100's of microsecs
in the ISR. The FPGA logic would off load this.
Having done it the hard way those 8042 devices look real nice. I have
a real respect for the code in those things.
Bob Kondner
"J.D. Bakker" wrote:
>
> [Hope this is not too off-topic...]
>
> Hi all,
>
> I'm designing an embedded StrongARM-based system[1] that I want to use with
> Linux. I need to design a keyboard/mouse interface for this beast, and
> going by the kernel sources PS/2 seems the way to go (I'd really like to
> use commodity hardware to talk to X and friends).
>
> I've since found notes on how to capture a PS/2 stream with a
> microcontroller, but I don't know what the best interface is to offer
> Linux, ie what should the hardware look like when seen from the kernel .
> I'd rather not use an 8042 ;-), but I'm open for other suggestions. The
> StrongARM has an I/O space that is almost but not entirely unlike ISA, and
> I have some GP I/O pins to spare. Does anyone have an idea what the best
> interface would be ?
>
> Sincerely,
>
> Jan-Derk Bakker
>
> [1] the Linux Advanced Radio Terminal or LART; 32MB, >200MIPS, <1W,
> pictures at http://www-ict.its.tudelft.nl/~erik/open-source/LART/ . I'd
> like to release the hardware design under a GPL-like license; please
> contact me off-list if you have any suggestions on the legalese that is
> unavoidably involved.
>
> --
> "... I've seen Sun monitors on fire off the side of the multimedia lab.
> I've seen NTU lights glitter in the dark near the Mail Gate.
> All these things will be lost in time, like the root partition last week.
> Time... to die...". - Peter Gutmann in the scary devil monastery
>
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