Debug serial console not working

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Vinayakumar Chikkadi

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Jul 2, 2021, 6:14:35 AMJul 2
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Hi

I am trying to get the debug serial working on Ubuntu for my beagle bone black board.

I am powering up the BBB with the 5V 2A power adapter. 

I am using the prolific usb to serial connector. After I connect the usb cable & When I check on Ubuntu with dmesg | tail
I could see it’s getting enumerated as ttyUSB0 
When I open with putty on the path 
/dev/ttyUSB0 with 115200 8N1
I am not able to open the com port using putty.

Kindly suggest if any of the steps missing out here.

Best regards,
Vinay

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Mark Lazarewicz

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Jul 2, 2021, 11:13:40 AMJul 2
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Try this


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Dennis Lee Bieber

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Jul 2, 2021, 1:45:00 PMJul 2
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On Fri, 2 Jul 2021 15:44:12 +0530, in gmane.comp.hardware.beagleboard.user
Vinayakumar Chikkadi <vinayvkc-Re5JQE...@public.gmane.org>
wrote:


>I am using the prolific usb to serial connector. After I connect the usb

WHICH "prolific usb to serial"? They have a whole slew of different
models. And that doesn't count the packagers using a Prolific chip in their
products (cf:
https://www.amazon.com/prolific-usb-serial/s?k=prolific+usb+to+serial )
I'm guessing something similar to
https://www.amazon.com/Serial-Adapter-Signal-Prolific-Windows/dp/B07R8BQYW1/ref=sr_1_8?dchild=1&keywords=prolific+usb+to+serial&qid=1625245702&sr=8-8

I can't really help with Prolific -- most of my USB<>serial devices are
FTDI chips. I think the Adafruit 4-pin cable is the only Prolific chip
device I have.

>cable & When I check on Ubuntu with dmesg | tail
>I could see it’s getting enumerated as ttyUSB0
>When I open with putty on the path
>/dev/ttyUSB0 with 115200 8N1
>I am not able to open the com port using putty.

Do you have privileges for the device? May not be relevant, but
connecting a USB<>Serial to the USB side of my BBB (I don't have a native
Linux desktop computer, and Windows won't be helpful to you) shows up like

crw-rw---- 1 root dialout 188, 0 Jul 2 13:21 /dev/ttyUSB0

the default user for the machine does belong to the dialout group.

I got the same thing for Debian running inside VirtualBox /after/
manually selecting the USB device from the VB0x menu...

BUT... unlike the BBB, my user account under VBox does NOT belong to
the dialout group, so I would have not permission to use it without making
changes...

crw-rw---- 1 root dialout 188, 0 Jul 2 13:31 /dev/ttyUSB0
wulfraed@debian:~$ groups
wulfraed cdrom floppy sudo audio dip video plugdev netdev bluetooth lpadmin
scanner vboxsf
wulfraed@debian:~$ sudo usermod -a -G dialout wulfraed
[sudo] password for wulfraed:

<logout, login>

wulfraed@debian:~$ groups
wulfraed dialout cdrom floppy sudo audio dip video plugdev netdev bluetooth
lpadmin scanner vboxsf
wulfraed@debian:~$



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Dennis L Bieber

Mark Lazarewicz

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Jul 2, 2021, 7:35:05 PMJul 2
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Vinayakumar Chikkadi

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Jul 3, 2021, 1:35:59 AMJul 3
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Hi Dennis, 

Good day to you

I have given permission by running

sudo chmod 0777 /dev/ttyUSB0 

Now I am able to open in putty but not receiving any data from bbb. Seems the issue with usb to serial cable.

I got similar cable what you just mentioned on amazon. 

Probably I would try to procure one from adafruit. 

Thank you, it was of great help to me.
I would check with different cables and come back if problem persists.

Regards,
Vinay


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Vinayakumar Chikkadi

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Jul 3, 2021, 1:40:29 AMJul 3
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Hi Mark,

Good day to you

Saw this article it would help me to procure one.

Thanks for your inputs.

Regards,
Vinay

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Mark Lazarewicz

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Jul 3, 2021, 9:49:04 AMJul 3
to beagl...@googlegroups.com, Vinayakumar Chikkadi
Hi Vinay

For future reference if you use a Ubuntu VM serial window the terminal can have no info like you see because the USB driver is claimed by Windows.

That can be fixed in the VM  but in my experience the connection can be intermittent when using VM.

 The nice thing about using Ubuntu VM is you could check your cable in Windows first  and then get the appropriate drivers  installed ( test cable).

 Something to keep in mind for future. 

The VM approach has issues with creating SD cards so yet another option is a dual boot Ubuntu/ Windows PC .

Best wishes on finding a cable quickly. I'm sure you are excited to play with your board.

Mark

Dennis Lee Bieber

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Jul 3, 2021, 11:45:03 AMJul 3
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On Sat, 3 Jul 2021 11:05:35 +0530, in gmane.comp.hardware.beagleboard.user
Vinayakumar Chikkadi <vinayvkc-Re5JQE...@public.gmane.org>
wrote:

>I have given permission by running
>
>sudo chmod 0777 /dev/ttyUSB0
>
That is not the preferred way to do it. The preferred way is by adding
your user account to the /group/ that owns tty* devices. On the systems I
checked, that is the Dialout group.

>Now I am able to open in putty but not receiving any data from bbb. Seems
>the issue with usb to serial cable.
>
Personally, I'd first connect an oscilloscope to the TxD and RxD pins,
and see what, if anything, is on those pins. You likely won't be able to
"read" the traffic, but should be able to recognize start/data/stop bits on
the scope.

Make sure you have the correct pins connected, and in the correct
direction...


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Vinayakumar Chikkadi

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Jul 5, 2021, 4:04:52 AMJul 5
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Hi Dennis, mark,

I could get the debug serial console working.
It was due to the faulty cable, it was the usb to serial with 6 pin connector, 


which connects to the jumper J1 on BBB. The order of the pin on the cable was different to the order on the jumper J1 header on the BBB board.

The pin positions for 5v, gnd, Rx, Tx on cable are not matching with J1 header on bbb.

Thank you so much
Have a great day.

Best regards,
Vinay

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Dennis Lee Bieber

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Jul 5, 2021, 12:58:20 PMJul 5
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On Mon, 5 Jul 2021 13:34:17 +0530, in gmane.comp.hardware.beagleboard.user
Vinayakumar Chikkadi <vinayvkc-Re5JQE...@public.gmane.org>
wrote:

>The pin positions for 5v, gnd, Rx, Tx on cable are not matching with J1
>header on bbb.
>

5V is a danger already... A Raspberry-Pi serial<>USB (came with a
Sparkfun Pi-Wedge) runs
DTR Rx Tx 3.3V CTS GND
Which is NOT compatible with BBB (the Rx and Tx are swapped).

https://elinux.org/Beagleboard:BeagleBone_Black_Serial
"The debug cable is a standard FTDI to TTL cable. Make sure you get the
3.3V version."

Personally, the AdaFruit cable is probably more flexible as the four pins
are free to connect anywhere, not tied to a specific sequence in one
header.



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Mark Lazarewicz

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Jul 5, 2021, 3:23:25 PMJul 5
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Hello Vinay

Good News. I offer some good advice.

If your career path is embedded software engineer as opposed to Linux application programmer buy these Jumper's.

You could have fixed your cable easily but more importantly you can hook up o scope and logic analyzer and probe connectors.

Today's logic analyzer very cheap used to be very expensive they also decode protocol's

Cheers

Here are Jumper's you could also make these soldering is also a good skill to have in your toolkit


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