Hi,
My comments are in-line.
On 20/12/2020 22:54, Dennis Lee Bieber wrote:
On Sat, 19 Dec 2020 02:16:56 -0800 (PST), in
gmane.comp.hardware.beagleboard.user "robert.berger"
<[email protected]> wrote:
There is a distinct lack of information in this post.
Hi,
I tried in a couple of ways to get something out of the serial console
while booting (U-Boot, kernel, console,..)
Which Beagle are you using?
Pocketbeagle
I posted it under "pocketbeagle" and thought that would be more obvious,
but it does not seem to be.
This seems extremely unstable and random.
What results have you obtained that cause you to make that statement.
screen /dev/ttyUSB4 115200
From "nothing" to some gibberisch (non ASCII characters, sometimes some
ASCII characters)
after the board is booted screen /dev/ttyACM0 115200 works fine, but
that's NOT what I want.
Presuming you are wired properly to the board,
That could be one problem, I guess, hence I am searching for a device
which might work, as already indicated in another reply and the docs[3][4]
[3] https://shop.mikroe.com/ftdi-click
[4]
https://www.ftdichip.com/Support/Documents/DataSheets/Cables/DS_TTL-232R_RPi.pdf
I wired
Board Adapter
Txd Rxd
Rxd Txd
GND GND
For the RS232 solution I also added 3.3V.
I don't dare to switch from 3.3 to 5V, since this could cause damage.
and configured the USB side
for the serial bit rate*, anything the board sends on the UART should be
available via the virtual serial port on the USB side.
Not really everything the board sends. Out of the box only stuff from
the time the "virtual" serial port starts.
I see the "virtual" serial port, but I would like to see the "console"
output starting from the first line of MLO.
debian@beaglebone:~$ cat /proc/cmdline
console=ttyO0,115200n8 root=/dev/mmcblk0p1 ro rootfstype=ext4 rootwait
coherent_pool=1M net.ifnames=0 lpj=1990656 rng_core.default_quality=100
quiet
I am also a bit confused about the ttyO0, although there is also a ttyS0;)
So I am not sure which one is supposed to be the "real" serial.
One device I tried is this[1] with 3.3V.
Another device is this[2].
Can you please advise which serial adapter to use?
Given how most computers have been dropping RS-232 connections, #2
seems to be an exercise in futility -- You have a 3.3V TTL UART being
converted to full 9-pin RS-232, only to then need an RS-232 to USB adapter
to connect to modern computers.
Not really.
1) Quite a few boards have TTL or real RS-232 outputs. So why go to USB
and not directly to good old RS-232?
2) I have a board farm and console servers with RS-232 connectors (RJ45
connectors with RS232 signals), which would be my preferred solution.
Unfortunately some newer boards only have USB connectors. Those I
connect via USB cables to USB hubs. But in any case I would like to see
the complete boot log (from MLO) and not just when the kernel is available.
* The USB protocol itself does not care about bit-rate -- it works in USB
speed packets. However, the chip-set on the adapter needs to be told what
bit-rate the far end is sending...
Regards,
Robert
--
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