uCLinux

This is taken from http://www.nioswiki.com/operatingsystems/uclinux/compilehello

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IO programming in user space.

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Note, you are doing in user space, with uclibc and included from /opt/nios2/include. It is not kernel space. You can not use interrupt. You can not use nios2 HAL, either.

You should know about the cache in Nios II. (BadOman:?) The first 2GB of address space is cached. The second 2GB is non-cached. These are not two seperate memory spaces or anything so there is a total of 2GB of address space (mirrored memory). This only applies for Nios II Full version with Data Cache. Nios II Standard version is uncached, so there should be no problems.

In other words address 0x00000000 (cachable) maps to address 0x8000000 (non-cachable)

" " " " " " 0x00000001 " " " " " " " " 0x8000001 (and so on .....)

So use the first 2GB for non-peripheral access (local memory), and the second 2GB for peripherals

You can define memory pointer access, and you can make it uncached by setting address bit 31.

eg, 0x00004000 -> 0x80004000

Or use port address defined in nios2_system.h, eg na_button_pio.

# include </home/hippo/uClinux-dist/linux-2.6.x/include/nios2_system.h>

# define inw(port) (*(volatile unsigned *)(port)) # for io read,

# define outw(d,port) (*(volatile unsigned *)(port))=(d) # for io write,

As an alternative, you can use these two defines (which are always uncached), they are similar to the Nios2-IDE functions :

# define IORD(address,offset) (*(volatile unsigned *)(((address)|0x80000000)+4*(offset)))

# define IOWR(address,offset,value) (*(volatile unsigned *)(((address)|0x80000000)+4*(offset)))=(value)

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So you can access with two last macros, like with nios2eds, your hardware in user space.

In case of interrupt you must handle it in kernel space, so you must write a driver (http://www.nioswiki.com/operatingsystems/uclinux/moduleprogramming)

as i see, your input device is a button-pio, check this file in you uclinux distro.

\linux-2.6\drivers\char

it could help.