Possible bug and lacking feature in BBB bsp, GPIO API hooks

[Gedare Bloom]

This problem indicates a lack of clear documentation. Steve, where did
you look for guidance on using the API?

On Sat, Oct 31, 2015 at 5:11 AM, Ketul Shah <ketulshah1993 at gmail.com> wrote:
> Hi Steve,
>
> I suggest you to kindly configure GPIO API by using following functions in
> your code,
>
> rtems_gpio_initialize();
> rtems_gpio_request_pin(.....);
>
> After using it should work properly. Me and Ben had tested on our BBBs.
>
> For example code you can have a loot at link.
>
> Hope this helps.
>
> Thanks,
>
> Ketul
>
> On 31 October 2015 at 05:11, Steve B <sbattazzo at gmail.com> wrote:
>>
>> Hi again guys,
>> I've noticed an unexpected (to me) behavior in the GPIO API for Beaglebone
>> Black.
>>
>> I borrowed a periodic task from the clock test source, and set it up to
>> toggle the GPIOs once every couple seconds.. here's what I have:
>>
>> rtems_task Test_task(
>>   rtems_task_argument task_index
>> )
>> {
>>   int task_count = 0;
>>   rtems_time_of_day time;
>>   rtems_interval    ticks;
>>
>>   ticks = task_index * 2 * rtems_clock_get_ticks_per_second();
>>
>>   for ( ; ; ) {
>>     task_count++;
>>     (void) rtems_clock_get_tod( &time );
>>     if ( time.second >= 35 ) {
>>       puts( "*** END OF CLOCK TICK TEST ***" );
>>       //exit( 0 );
>>       while(1);
>>     }
>>     put_name( Task_name[ task_index ], FALSE );
>>     print_time( " - rtems_clock_get_tod - ", &time, "\n" );
>>
>>     //Toggle GPIO
>>     if(task_count & 1) {
>>         rtems_gpio_set(LED1);
>>         rtems_gpio_set(LED2);
>>         }
>>     else rtems_gpio_clear(LED1);
>>
>>     (void) rtems_task_wake_after( ticks );
>>   }
>> }
>>
>> Notice I've defined that if the least significant bit of my variable
>> task_count is 1, then I set both LED1 and LED2. If that LSB is zero, I just
>> call to clear LED1.
>> When I actually run this, both LED1 and LED2 are being cleared! Same is
>> true with the 3rd and 4th user LEDs as well, if I happen to set all four of
>> them. So I think somehow rtems_gpio_bsp_clear() is clearing the entire bank,
>> not just the single pin specified in the argument. Can somebody confirm this
>> behavior?
>> I will dig around and see if I can figure out why it's happening and
>> generate a patch if I find it.
>>
>> Also, I was hoping to be able to toggle a GPIO output by checking its
>> current state and using that to decide whether to set or clear, but I don't
>> see anything in the API that would allow me to check the state of an output.
>> Is this a known/intended limitation?
>>
>> Cheers,
>>
>> Steve
>>
>>
>>
>>
>> _______________________________________________
>> users mailing list
>> users at rtems.org
>> http://lists.rtems.org/mailman/listinfo/users
>
>
>
> _______________________________________________
> users mailing list
> users at rtems.org
> http://lists.rtems.org/mailman/listinfo/users