You can try only map 4Bytes
2015-05-22 3:13 GMT+08:00 Jacek Radzikowski jacek.radzikow...@gmail.com:
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, ja...@dfsoftware.com 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
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