Sam,

> From: yocto-boun...@yoctoproject.org [mailto:yocto-boun...@yoctoproject.org] 
> On Behalf Of SAS NONE
> Sent: Wednesday, July 01, 2015 12:36 AM
> To: yocto@yoctoproject.org
> Subject: [yocto] SAMA5D3 header files for C application development
>
> Hi,
>
> I'm using SAMA5D3-xplained board and built a Linux kernel 3.18 distro for it 
> using the Poky Yocto build directory.  I've also created the sdk and 
> installed it in /opt/poky-atmel/1.7.2.  Ran hello world example in eclipse 
> however I'm trying to find the C header files for the peripherals so I can 
> develop applications using the SPI bus or the i2c bus.  Any help in locating 
> these header files or how to go about developing and cross compiling the C 
> code in eclipse?  I've already looked at the Yocto adt manual for eclipse 
> which is very minimum.
> 
> Any help is greatly appreciated.

I'm assuming based on your questions that you are new to the device tree setup 
for ARM in the Linux kernel and how to make use of it on the kernel side and 
the userspace side.  If so, I'd suggest you go to 
http://www.at91.com/linux4sam/bin/view/Linux4SAM/LinuxKernel and read the 
documentation linked in the "Changes introduced by Device Tree Support 
section".  Then Atmel has documentation specific to their SPI and I2C with the 
Linux kernel documentation.  Look under 
Documentation/devicetree/bindings/spi/spi_atmel.txt and 
Documentation/devicetree/bindings/i2c/i2c-at91.txt in your kernel source.

In summary, if you are lucky enough that the device you want to communicate 
with has device tree support, then you would add that device to your device 
tree files and follow their documentation on how to communicate with it from 
userspace.  For example, I am using the AD5446 DAC on my hardware, and Analog 
Devices has excellent documentation of their DAC Linux kernel driver here: 
http://wiki.analog.com/resources/tools-software/linux-drivers/iio-dac/ad5446.  
For this device I open up a file and write a value for the desired output 
voltage, and then the driver takes care of communicating to the AD5446.  
Otherwise I think you can use the generic spidev interface for reading and 
writing data on the SPI port (and I think there is something similar for I2C?).

Since you have questions that are specific to your hardware, I think you may be 
able to get better answers on Atmel's AT91 forums or checking for information 
on Linux kernel driver support for your specific I2C and SPI devices.  If you 
are having problems building an application with the Eclipse ADT and getting to 
run on your hardware, then let us know some specific details with the problems 
you are seeing.

Regards,
Bryan

> 
> Thanks,
> 
> Sam
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