Re: i2c driver for at91sam7x

Re: i2c driver for at91sam7x

[Andrew Lunn]

On Fri, Nov 07, 2008 at 08:39:23PM +0530, vibisreenivasan wrote:
> hello,
> 	Is there any one working on i2c bus driver for at91sam7x.

I know eCosCentric have one, but you need to pay for that. 

Other people have mentioned writing i2c drivers as well.

However, you need to be careful. The i2c hardware is broken. The Linux
kernel marks it as such. See:

http://www.at91.com/samphpbb/viewtopic.php?t=4665&sid=1032a7cdc95b571dc784adb204d78d33

From what i understand, if you are doing transfers of 1 byte, it is
O.K, but multiple byte transfers can break.

Writing a GPIO based driver should be reasonably easy as far as i
understand and does not suffer from these problems.

        Andrew

Re: i2c driver for at91sam7x

[Tom Deconinck]

On Fri, Nov 7, 2008 at 5:14 PM, Andrew Lunn <andrew@lunn.ch> wrote:
>
> On Fri, Nov 07, 2008 at 08:39:23PM +0530, vibisreenivasan wrote:
> > hello,
> >       Is there any one working on i2c bus driver for at91sam7x.
>
> I know eCosCentric have one, but you need to pay for that.
>
> Other people have mentioned writing i2c drivers as well.
>
> However, you need to be careful. The i2c hardware is broken. The Linux
> kernel marks it as such. See:
>
> http://www.at91.com/samphpbb/viewtopic.php?t=4665&sid=1032a7cdc95b571dc784adb204d78d33
>
> From what i understand, if you are doing transfers of 1 byte, it is
> O.K, but multiple byte transfers can break.
>
> Writing a GPIO based driver should be reasonably easy as far as i
> understand and does not suffer from these problems.
>
>        Andrew

I have written such a driver some time ago, but I changed jobs since,
so I don't have access to the source anymore.
My experience: use GPIO and the eCos bit-banging interface, since the
hardware implementation is seriously broken.
The driver I wrote didn't work well using interrupts (latency problems
combined with a 'smart' hardware implementation that decides to
generate stop-conditions by itself, breaking multy-byte transfers,
etc.) It did work in polling mode.

Tom