2009-03-09 10:29:50     Time between reading of spi

Document created by Aaronwu Employee on Aug 14, 2013
Version 1Show Document
  • View in full screen mode

2009-03-09 10:29:50     Time between reading of spi

Samuel Coelho (BRAZIL)

Message: 70615   

 

Hi all.

 

I have a BF527 Ezkit and uClinux 2008 R1.5-RC3.

 

I wrote a program test to read one AD over SPI. The program works fine.

 

I can change the clock of SPI in the config file of board (~/uClinux-dist-2008R1.5-RC3/linux-2.6.x/arch/blackfin/mach-bf527/boards/ezkit.c). If I change the SPI clock, the time between reads don't change.

 

My code:

 

    ...

 

    fd = open("/dev/spi", O_RDWR);

    if (fd < 0) {

        perror("Error opening /dev/spi");

        return 1;

    } else {

        printf("spi(%d) opened\n", fd);

    }

 

    for (i=0; i< loops; i++) {

      

        status = read(fd, rbuf, len);

        if (status < 0) {

            perror("Error read");

            if (fl) {

                fclose(fl);

            }

            return 1;

        }

        if (status < len) {

            fprintf(stderr, "Short read\n");

            return 1;

        }

 

        fprintf(fl, "%d;", rbuf[0]);

    }

 

 

My doubt is how can I set the time between reads of SPI.

 

 

 

Best regards, Samuel.

QuoteReplyEditDelete

 

 

2009-03-09 18:42:50     Re: Time between reading of spi

Mike Frysinger (UNITED STATES)

Message: 70629   

 

so add a sleep() ?

QuoteReplyEditDelete

 

 

2009-03-10 15:42:16     Re: Time between reading of spi

Samuel Coelho (BRAZIL)

Message: 70720   

 

Hi Mike.

 

Thanks for your answer.

I want reduce the time.

I took the writing in file (fprintf(fl, "%d;", rbuf[0]);) of loop and the time decreased.

But I don't know how control the time.

 

Regards, Samuel.

 

QuoteReplyEditDelete

 

 

2009-03-10 15:47:26     Re: Time between reading of spi

Mike Frysinger (UNITED STATES)

Message: 70722   

 

there are delays caused by userspace overhead and working with other SPI devices

QuoteReplyEditDelete

 

 

2009-03-10 16:03:58     Re: Time between reading of spi

Samuel Coelho (BRAZIL)

Message: 70723   

 

Ok, I understood.

 

Thanks Mike.

Attachments

    Outcomes