Uboot won't boot when a device is connected on serial port

[freebsd at casidy.com]

Hi,


I exposed my problem of getting back the serial port on a Raspberry 2 in 
"Liberate the serial port".

My problem is in fact getting worse.

I realised that I cannot boot my Pi2 when I have a device connected on a 
serial port. The boot process breaks: it looks like Uboot is considering 
that someone typed in some characters...


How can I have uboot ignoring the serial port?

I have installed 11.0-RELEASE-p1.


Thanks


Philippe.



On 07/04/2017 17:31, freebsd at casidy.com wrote:
> Hi,
>
>
> I have a Raspberry Pi2 and I am struggling at using the serial port 
> uart0 for my own purpose.
>
> I have install 11.0-RELEASE-p1 a few months ago and now I have 
> attached a device that send characters on the Raspberry uart0 and I 
> try to read them by a
>
> setting the tty
>
> stty -f /dev/ttyu0 1200 sane evenp parenb cs7 -crtscts
>
>
> trying to read
>
> cat /dev/ttyu0
>
> or cat < /dev/ttyu0
>
>
> But my understanding is that the kernel at some point grabbed uart0 to 
> provide a serial console.
>
>
> I tried to change /etc/ttys
>
> ttyu0   "/usr/libexec/getty 3wire.115200"       vt100   off secure
>
> but no avail, I have nothing while trying to cat /dev/ttyu0.
>
>
> I tried with Raspbian, and after disabling the use of the uart as a 
> console on boot, I have been able to get my characters... so the 
> hardware works fine.
>
>
> How can I use my serial port for another purpose than a serial console?
>
> What am I missing?
>
>
> Thanks in advance,
>
> Philippe
>