On 9/7/2013 8:18 AM, John Prentice (FS) wrote:
> Greetings
> 
> Can someone please help me understand how the hal_pru_generic driver/comp,
> called with a number of stepgens= and pwmgens=, ends up mapping the
> generated signals to  hardware pins on the BBB headers (or chip)? Similarly
> how does the hal_bb_gpio mapping work?
> 
> TIA and apologies if I am missing something obvious.

There are far too many pin naming schemes for the BeagleBone, including
two new ones used by the LinuxCNC Beaglebone code.

Short answer:
============
Read the code (sorry!)


Medium answer:
============
The PRU code uses an integer value that equals the kernel GPIO number
plus 32 (so that zero means "don't twiddle *ANY* pins!").  The values
are also extended, and what would be the non-existing GPIO bank 4 means
"Use the PRU direct I/O pins".

The hal_bb_gpio pin numbers is:

1xx = P8
2xx = P9
 xx = connector pin number


Long Answer:
============
I really need to make a blog page about pin numbering.  There's some
data in Brandon Heller's post about home/limit switches:

http://bb-lcnc.blogspot.com/2013/07/adding-homelimit-switches.html

I'll try to get something posted tonight...

-- 
Charles Steinkuehler
[email protected]

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