Re: speed of /dev/i2c-2 in imx6q sabre-lite

[Eric Nelson <eric.nelson@boundarydevices.com>]

Hi Thanassis,

On 08/13/2013 11:03 AM, Thanassis Silis wrote:
> Hello everyone,
> I am unaware as to who sets clock speed on the i2c bus and specifically
> on the /dev/i2c-2 which is exposed on the board so as to drive external
> equipment.
 >
> I am looking into the linux-boundary kernel files in yocto (dylan) build
> dir, but I cannot figure out where that is set.
> To be honest I don't even know if i'll find that info there, but it
> seems like the right place to start (after googling about it of course).
>
> So who determined the speed (standard mode, fast mode, etc) for the
> external i2c? if it is a driver , which one should I be looking for?
>

This structure defines the speed of the I2C bus:
	https://github.com/boundarydevices/linux-imx6/blob/boundary-imx_3.0.35_4.0.0/arch/arm/mach-mx6/board-mx6_nitrogen6x.c#L434

To change it for i2c-2 by itself, you'll need to make a copy of
that, change the speed value and pass the copy to the routine
imx6q_add_imx_i2c():
	https://github.com/boundarydevices/linux-imx6/blob/boundary-imx_3.0.35_4.0.0/arch/arm/mach-mx6/board-mx6_nitrogen6x.c#L1320

> The reason is I am trying to drive some TMC222 low-power stepper motor
> control ICs, but they do not respond.
> Note I have successfully connected a number of other i2c ICs (among
> others the pca9505x).
>
> An answer is not necessary. Any pointers as to how to go about it , so I
> can learn about this is more than welcome.
> Thank you for your help.
>

This should be straightforward.

Let me know if you have any trouble.

Regards,


Eric