Geode SC1100 i2c bus

[Milan Obuch]

On Saturday 03 February 2007 17:10, Cats wrote:
> Hello all,
>

Hi,

> I've been looking for some technical infos and/or driver for the i2c bus on
> the Geode SC1100 processor under FreeBSD 6.
>

I tried it too, but no success yet, partially due to ENOTIME :(

> I found i2c stuff, tried to compile a kernel with it but nothing showed up.
> I had a look at the sources and apparently it doesn't hook up to isa bus.
>

There is no driver yet.

>  From the geode databook, on page 11, i2c bus that is called ACB bus is in
> the superIO block. This superIO block is attached on the isa bus.
>

Geode has hardware i2c controller.

> The ACB is at the same level than Uart, so I had a look at sio source and
> got a big headache. I'm not really used to drivers nor kernel programming
> stuff, that's why I need your help.
>

Why do you compare ACB and UART? In FreeBSD, sio is serial i/o controller, not 
superIO, maybe you are confused... ACB and UART does not have much in 
common...

> My goal is to use the i2c bus on a wrap board to supervise voltages, pilot
> a servo motor and so on. I do not want to use USB because it's easier with
> i2c and I already have i2c hardware ready.
>
> Does someone already tried to use i2c bus on a wrap board under FreeBSD ?
>

Well, the best I achieved was working bit-banged i2c for wrap's onboard lm77. 
I was able to read temperature and that's all. Unfortunatelly, external i2c 
bus works only with geode's hardware i2c controller, which I did not got into 
working state, internal bus can be switched into gpio mode, which works for 
me. But that is not really usefull.

> I had a look at openbsd and looks like it has already i2c support, but I
> ain't had time to build a system and test it on the wrap. For now all my
> wrap boards run flawlessly with FreeBSD.
>

I looked there too, but OpenBSD has different infrastructure, and porting is 
not easy, at least for me. They have even some more Geode's resources 
working, but, again, porting is not easy for me.

> I searched the mailing list archive but did not found something that could
> help me. Remember I'm not really good at writing drivers stuff. I'd like to
> learn but I have no start point.
>

All I can offer is bit-banged stuff, which I got into working state...

Regards,
Milan

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