Re: Doubts in getting started with the Analog AD7928 driver

[Daniel Junho <djunho@gmail.com>]

On Tue, Sep 17, 2019 at 3:24 AM Ardelean, Alexandru
<alexandru.Ardelean@analog.com> wrote:
>
> On Mon, 2019-09-16 at 20:50 -0300, Daniel Junho wrote:
> > [External]
> >
> > Hello everybody.
> >
> > I am still learning about kernel developing. I would like to try to
> > develop a device driver for the AD7928 [1], from Analog Device.
> >
> > Can someone give some words to guide me?
> >
> > I was thinking about forking the analog kernel repo [2] but I don't
> > know to which branch should I commit to when doing a pull request. Or
> > if this is the correct way for the devices from Analog.
> >
>
> Hey,
>
> Thanks for the interest in writing the driver for this.
>
> In some cases, some new parts may have an existing driver available already
> that can be re-used partially or completely.
>
> You're in luck.
> There is driver seems to be partially implemented via
> drivers/iio/adc/ad7923.c
>
> I've done only a minor/quick check but the control register bits are
> compatible for the AD7928 as well.
>
> Typically, you can extend that driver and add the new parts and test them.
>
> So, my suggestion would be:
> 1. Get an eval-board or a AD7928 part; depending on the case we could help
> with this
> 2. Try to set it up with a Raspberry Pi with the eval board
>    a. it looks to me that you need a 7V-9V power-supply
>    b. you can hook the SPI to the test-points on the eval board
> 3. Write a basic device-tree overlay ; you can adapt something from other
> examples.
> Look here:
> https://github.com/analogdevicesinc/linux/blob/rpi-4.19.y/arch/arm/boot/dts/overlays/Makefile
> Usually  rpi-adXXX.dts  are ADI parts.
> 4. Enable the driver for the kernel.
> If using the ADI kernel, there's a guide here for RPi.
> https://wiki.analog.com/resources/tools-software/linux-build/generic/raspberrypi
> Check the branch that matches your Raspbian image (rpi-4.19.y is the
> latest)
> 5. Build the kernel
> 6. Write it to the SD-card image
> 7. Test
> 8. Modify & repeat
>
> Thanks
> Alex
>
> > [1] https://www.analog.com/en/products/ad7928.html
> > [2] https://github.com/analogdevicesinc/linux
> >
> > Daniel Junho

Hi Alex.

It seems that using AD7923 will be the best choice. They are very similar.

Thank you for your reply and suggestion.
I don't have an EVB, but at work, we have a board with the AD7928
using a user driver. So I will try to use it for this development, at
least for now.

I believe that will be fun =)

Daniel Junho