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

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Fri, Oct 11, 2024 at 09:36:07AM -0400, Mouse wrote:
> > From the schematic here:
> > https://github.com/beagleboard/BeagleBone-Black/blob/master/BBB_SCH.pdf
> > there is a pulldown resitor on UART0_RX input.
> 
> You call it a pulldown, not a pullup, so I infer it's pulling the pin
> to a more-negative voltage level.
> 
> In RS-232, the more negative level is marking, in which case that is
> not a problem; that's the correct way to pull it.  But since you say
> 
> > The solution is to either rebuild a kernel without DDB, or tie
> > UART0_RX to a +3.3V pin.
> 
> I also infer that it is a logic-level signal, not an RS-232-level
> signal.  (3.3V is, just barely, within the defined range for RS-232,

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)

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--