SPI interface using /dev/mem

vijeshreddy — Thu, 31 Aug 2017 07:50:01 GMT

I am trying to configure SPI registers using /dev/mem in imx6. I am able to toggle an led by configuring the GPIO registers using /dev/mem but I am unable to configure SPI.

Following steps I have done.

1. using mmap i have mapped the address 0x200C000 and configured ECSPI2_CONREG for chip select 0.

2. using mmap i have mapped the address 0x20E0000 and configured the IOMUX PADS for SPI2

3. using mmap i have mapped the address 0x200C000 again and configured ECSPI2_CONREG. (loaded (ECSPI2_TXDATA) and enaled xch bit in ECSPI2_CONREG.). I am transmitting continuously in a while loop.

4. I am unable to see any transitions on CS signal and no clock is generated on SCLK.

Is the above configuration method correct ?? am I missing any thing in configuring the SPI , I have not configured any clock registers .

If any sample code for SPI initialization is available please provide.

Thanks in advance.

my code :

int spi_fd = open("/dev/mem",O_RDWR|O_SYNC);
        if(spi_fd < 0)
        {
             printf("Can't open /dev/mem\n");
             return 1;
        }
        spi_reg = (unsigned int *) mmap(0, getpagesize(), PROT_READ|PROT_WRITE, MAP_SHARED, spi_fd, 0x200C000);

       if(spi_reg == NULL)        {
           printf("Can't mmap1\n");
           return 1;
       }

       for(i =0; i<10; i++)
       {
           printf("value = %x\n", spi_reg[i]);
       }

/* Configuring SPI*/

spi_reg[2] = 0 ;
spi_reg[2] = 0x7000f1 ;

/* mapping IOMUX*/

spi_reg = (unsigned int *) mmap(0, (2*getpagesize()), PROT_READ|PROT_WRITE, MAP_SHARED, spi_fd, 0x20e0000);

        if(spi_reg == NULL)
        {
            printf("Can't mmap2\n");
            return 1;
        }

       spi_reg[517] = 0x02 ;
       spi_reg[516] = 0x02 ;
       spi_reg[518] = 0x02 ;
       spi_reg[519] = 0x02 ;

        spi_reg[158] = 0x02 ;
        spi_reg[159] = 0x02 ;
        spi_reg[160] = 0x02 ;
        spi_reg[161] = 0x02 ;

/* Again mapping SPI registers */

spi_reg = (unsigned int *) mmap(0, getpagesize(), PROT_READ|PROT_WRITE, MAP_SHARED, spi_fd, 0x200c000);

       if(spi_reg == NULL)
       {
           printf("Can't mmap3\n");
           return 1;
       }

       spi_reg[1] = 0x21 ;
       spi_reg[9] = 0x21 ;
       spi_reg[2] = 0x7000f1 ;
       spi_reg[3] = 0xF00 ;

       while(1)
       {
           spi_reg[1] = 0x21 ;
           spi_reg[9] = 0x21 ;

/* xch enable */
           spi_reg[2] = 0x7000f5 ;
           sleep(1);
           spi_reg[6] = 0x80 ;
           printf("data sent\n");
       }

Re: SPI interface using /dev/mem

igorpadykov — Thu, 31 Aug 2017 23:21:56 GMT

Hi vijesh

for simple sample code for SPI initialization one can look at Github SDK
https://github.com/backenklee/swp-report/tree/master/iMX6_Platform_SDK
and spi example in unit tests (folder /mxc_spi_test):

imx-test
www.nxp.com/lgfiles/NMG/MAD/YOCTO/imx-test-5.7.tar.gz

Best regards
igor
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SPI interface using /dev/mem

Re: SPI interface using /dev/mem