On 7/10/2016 11:36 AM, Jacob Fish wrote:
> On a side note, why is there a ttyS* tied with the ttyO*? I'd always assumed 
> that those where devices indicating that there is a shell console tied with 
> the 
> UART port. After this quick test, it would seem like this is incorrect to 
> assume. I was able to use either ttyO1 or ttyS1 to communicate from BBB to 
> RPi 
> without any issues. Why is this there?

ttyS* basically means "serial port", not "serial console".  You won't
get a console unless you run getty (see the commented examples in
/etc/inittab for ttyS0 and ttyS1).

IIRC, the earlier BBB kernels used /dev/ttyO* port naming
(particularly prior to the TI Omap serial port driver being integrated
with the kernel serial driver).  I believe the symlinks are a
convenience to keep older code/documentation working.  Note the 3.x
series kernels have this somewhat confused with port names and
numbering changing between various kernel versions as the drivers were
being updated, but I believe the 4.x kernels should all use standard
/dev/ttyS* naming with consistent port numbering.

-- 
Charles Steinkuehler
[email protected]

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