Luigi very good, I also had this problem, and your solution worked for me
also.
But I still do not understand why it is necessary to export at least one
pin on each port to be able to access the GPIO with mmap.
Someone can explain me?
Em terça-feira, 11 de junho de 2013 23h41min10s UTC-3, Jacek Radzikowski
escreveu:
>
> Hello,
>
> I'm getting bus errors whenever my program tries to access registers
> controlling pins on GPIOs 0,2 or 3. I'm not trying to set pinmuxing, I
> try to write to registers controlling the pins.
> GPIO1 works fine and I can enable outputs by writing to the OE
> register and change the values on the pins by writing to the OUT
> register.
>
> Here are some details of my simple test program:
> The base addresses for the GPIO blocks are defined as follows:
> const uint32_t gpioAddrs[] =
> { 0x44E07000, 0x4804C000, 0x481AC000, 0x481AE000 };
>
> The memory blocks are mapped to process address space with the following
> mmap:
> gpios[i] = (uint32_t *) mmap(NULL, 0xfff,
> PROT_READ | PROT_WRITE, MAP_SHARED, gpioFd,
> gpioAddrs[i]);
>
> Printing values from OE, IN and OUT registers:
> printf("i=%i\n",i);
> printf("OUT[%i]=0x%08x\n",i,gpios[i][DATA_OUT_REG/4]);
> printf("IN[%i]=0x%08x\n",i,gpios[i][DATA_IN_REG/4]);
> printf("OE[%i]=0x%08x\n",i,gpios[i][GPIO_OE_REG/4]);
>
> The full source is on gist:
> https://gist.github.com/piranha32/4fd285cc8333eeb4ec39
>
> Program works fine when 'i' is set to 1, crashes for 'i' set to 0,2 or 3.
> Am I missing something obvious, or is this an overzealous memory
> protection?
>
> Board: BBBlack
> Kernel: Linux beaglebone 3.8.13 #1 SMP Fri Jun 7 09:49:12 CEST 2013
> armv7l GNU/Linux
>
> thx,
> j.
>
>
> --
> Given a choice between two theories, take the one which is funnier
>
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