Re: BeagleBone Black doesn't boot without serial console (10.0 release)

Mouse <[email protected]> wrote:
>>> I also infer that it is a logic-level signal, not an RS-232-level
>>> signal.
>> Yes, these are TTL-level signals.  I've never seen RS-232-level
>> signals in embeeded or developement boards (and if you connect theses
>> to a RS232 line you'll probably destroy your board)
>
> Depends on the current-carrying capacity of the protection diodes.
> RS-232 specifies some kind of limit; I forget whether it's a minimum
> output impedance or a maximum current-drive capability or what, but
> there is a limit.  Provided the protection diodes on the input pin can
> withstand that current without ill effect, you should be fine.  (Fine
> from the point of view of frying the hardware, that is.  It still won't
> produce enough voltage swing on lines driven by the TTL end to satisfy
> RS-232's voltage constraints and thus won't work reliably unless your
> RS-232 receivers happen to have a threshold which falls in the
> logic-level voltage range.)

Forget about RS-232.

Modern embedded boards are designed to be used with USB to serial
adaptors.