Hi , I know that was a similar topic but I need much more help so please be forgiving. I will add that I am unfortunately a beginner in the topic. I use the following set with ARM9 : http://www.propox.com/products/t_232.html?lang=en . Module is delivered with system Linux which is based on OpenWrt distribution. I need to build a measurement module, and most of the sensors are operating properly. I have a problem with one sensor, it needs get signal 32kHz . On my set is out (PB30) Programmable Clock Register 0, from what I see from the data sheet must enter a value of 0x0 to the registry PMC_PCK0. Next you need to set the PMC_SCRER and it should work? Here is the problem, do not know how to go about it ... you can probably set up registry from the console of Linux or the programs in C but I do not know how...Maybe someone could write me a C Program that runs the clock, I'll be very grateful. To compile I use arm-linux-gcc-4.1.2

I found something like this :

#include <stdio.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <unistd.h>
#include <linux2/i2c-dev.h>
#include <AT91SAM9260.h>

int main()
{

unsigned int pck = 1;
unsigned int mode = AT91C_PMC_CSS_SLOW_CLK | AT91C_PMC_PRES_CLK;

AT91C_BASE_PMC->PMC_SCDR = AT91C_PMC_PCK1;
AT91C_BASE_PMC->PMC_IDR = AT91C_PMC_PCK1;
AT91C_BASE_PMC->PMC_PCKR[pck] = mode; //set pclk mode
AT91C_BASE_PMC->PMC_SCER = AT91C_PMC_PCK1; //enable pclk clock

while(!(AT91C_BASE_PMC->PMC_SR & AT91C_PMC_PCK1RDY));

AT91C_BASE_PMC->PMC_SCDR = AT91C_PMC_PCK1;


}

but when I ran this I got : Segmentation fault

Some advice ?

The problem here is that Linux user space will not let you touch the peripheral registers directly, you would need to mmap() a region.

Generally it would be better to place code like this in a driver, or board specific initialization.

Another place to configure hardware is in the AT91BootStrap code, where you can touch hardware in this fashion.

#include <stdio.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <time.h>
#include <unistd.h>
#include <linux2/i2c-dev.h>
#include <AT91SAM9260.h>
#include <sys/mman.h>




#define MAP_SIZE 4096UL
#define MAP_MASK (MAP_SIZE -1)


int main()
{

int fd;
void *base;
FILE *outfile;
unsigned int pck = 1;
unsigned int mode = AT91C_PMC_CSS_SLOW_CLK | AT91C_PMC_PRES_CLK;

if((fd = open ("/dev/mem", O_RDWR | O_SYNC)) ==-1)
{

printf("NOT OK");
return -1;
}
printf("OK");

if((base =mmap(0, MAP_SIZE, PROT_READ | PROT_WRITE,MAP_SHARED,fd,(long int)AT91C_BASE_PMC & ~MAP_MASK)) == (void *)-1)
{
printf("NOT OK");
return -1;
}

printf("OK");

*(unsigned long int *)(base + 40) = AT91C_PMC_PRES_CLK_16 | AT91C_PMC_CSS_MAIN_CLK;
*(unsigned long int *)(base + 0) = AT91C_PMC_PCK0; //enable pclk clock

while(! ( (*(unsigned long int *) (base + 68)) & AT91C_PMC_PCK0RDY) );


//*(unsigned int *)(base + 4) = AT91C_PMC_PCK1;
//*(unsigned int *)(base + 64) = AT91C_PMC_PCK1;
//*(unsigned int *)(base + 40) = mode; //set pclk mode
//*(unsigned int *)(base + 0) = AT91C_PMC_PCK1; //enable pclk clock

// while(! ( *(unsigned int *) ((base + 68)) & AT91C_PMC_PCK1RDY));


printf("end");
}

it is ok ? What is wrong with this?