Clocks for some of the GPIO modules are not enabled by default, and accessing them will cause BUS error. The easiest workaround is to export one pin from each of the modules using /sys interface: https://groups.google.com/d/msg/beagleboard/OYFp4EXawiI/Mq6s3sg14HoJ Here is a short script which does the job: https://github.com/piranha32/IOoo/blob/master/tools/bbb_enable_gpio.sh
Regards, j. On Thu, May 21, 2015 at 2:59 PM, <[email protected]> wrote: > I've been working to get the access to the GPIO registers to replace the > existing sys access we are using now. However, I'm crashing accessing both > GPIO 2 and 3 (1 and 2 appear fine). I'm sure I'm just doing something > stupid. Here is some basic setup: > > __off_t MUX_OFFSET[] = { > 0x44E07000, // GPIO 0 > 0x4804C000, // GPIO 1 > 0x481AC000, // GPIO 2 > 0x481AE000 // GPIO 3 > }; > > struct MUX_LAYOUT > { > uint8_t *gpio_addr; > uint32_t *gpio_oe_addr; > uint32_t *gpio_setdataout_addr; > uint32_t *gpio_cleardataout_addr; > uint32_t *gpio_dataout_addr; > uint32_t *gpio_datain_addr; > }; > > MUX_LAYOUT MUXes[4]; > > #define GPIO_MEM_LENGTH 0xfff > #define GPIO_OE 0x134 > #define GPIO_SETDATAOUT 0x194 > #define GPIO_CLEARDATAOUT 0x190 > #define GPIO_DATAOUT 0x13C > #define GPIO_DATAIN 0x138 > > Then here is example code that will always crash on accessing GPIO 2: > > fd = open("/dev/mem", O_RDWR); > > for( size_t gpio = 0; gpio < 4; ++gpio) > { > MUX_LAYOUT& mux = MUXes[gpio]; > > mux.gpio_addr = (uint8_t*)mmap(0, GPIO_MEM_LENGTH, PROT_READ | > PROT_WRITE, MAP_SHARED, fd, MUX_OFFSET[gpio]); > > if(mux.gpio_addr == MAP_FAILED) > { > throw MSC_EXCEPTION("Unable to map texpr PIO"); > } > > mux.gpio_oe_addr = (uint32_t *)(mux.gpio_addr + GPIO_OE); > mux.gpio_setdataout_addr = (uint32_t *)(mux.gpio_addr + > GPIO_SETDATAOUT); > mux.gpio_cleardataout_addr = (uint32_t *)(mux.gpio_addr + > GPIO_CLEARDATAOUT); > mux.gpio_dataout_addr = (uint32_t *)(mux.gpio_addr + GPIO_DATAOUT); > mux.gpio_datain_addr = (uint32_t *)(mux.gpio_addr + GPIO_DATAIN); > > // Crashes here when gpio == 2 > uint32_t temp = *mux.gpio_datain_addr; > } > > In this case I'm crashing dereferencing gpio_datain_addr, but it will crash > accessing any of the pointers created when setting up GPIO 2 and 3. Any > thoughts? I'm running a relatively current debian build. > > Thanks for the help, > > Jared > > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. -- Given a choice between two theories, take the one which is funnier -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
