Getting Bootlogs on BeagleBone Black using USB Cable.Possible?

[Raul Piper]

HI,

I am new to this group.I am trying to boot a custom kernel which I have built using this link .I hard pressed the Button S2 while the board was booting from the MicroSD CARD (not the EMMC) but I see no display on HDMI connected TV and neither any LED is glowing except the Power LED(PWR).I want to see the boot logs and opened the minicom by connecting the USB cable to the BBB but can't see any boot logs on the minicom (@115200).Is it possible to get the boot logs using the USB cable or do I have to purchase "Serial Debug cable : for this like Standard FTDI Cable or Adafruit 4 Pin Cable (PL2303) or (USB to serial adapter) TTL-232R-3V3 at Digi-Key.

Please suggest.

-Rp

[Robert Nelson]

On May 4, 2016 11:50 PM, "Raul Piper" <raulpb...@gmail.com> wrote:
>
> HI,
> I am new to this group.I am trying to boot a custom kernel which I have built using this link .I hard pressed the Button S2 while the board was booting from the MicroSD CARD (not the EMMC) but I see no display on HDMI connected TV and neither any LED is glowing except the Power LED(PWR).I want to see the boot logs and opened the minicom by connecting the USB cable to the BBB but can't see any boot logs on the minicom (@115200).Is it possible to get the boot logs using the USB cable or do I have to purchase

No, is not possible.. That interface you are using is created by the kernel itself.. Way after it started booting...

"Serial Debug cable : for this like Standard FTDI Cable or Adafruit 4 Pin Cable (PL2303) or (USB to serial adapter) TTL-232R-3V3 at Digi-Key.

Correct, that's the cable you need.. 3.3v...

Regards,

[Raul Piper]

Thanks for the Prompt response.

I dont have that cable i mentioned above  right now.

But I tried the below two Hardware .

1. USB to RS-232 Converter  and connected DB9 connector pins GND,TX and RX with that of the BBB J1(cross fashion - TX-RX and vice versa) connector. My settings are 115200 8N1 @ /dev/ttyUSB0 .

I can see logs on minicom but they are all garbled.Are my Serial Port Settings correct.

2.Tin Flyswatter CAN 2 

Same settings and Hardware connections with it and getting the same result.

Or Do I need only the h.w I mentioned in my first post.

I believe the 1 , 2 h/w already have TTL 3v3 converter inside them?isn it?

[William Hermans]

1. USB to RS-232 Converter  and connected DB9 connector pins GND,TX and RX with that of the BBB J1(cross fashion - TX-RX and vice versa) connector. My settings are 115200 8N1 @ /dev/ttyUSB0 .

I can see logs on minicom but they are all garbled.Are my Serial Port Settings correct.

I use screen, and have tried minicon, but do not like minicon automatic screen size. Anyway, sometimes, and I'm not sure how both screen and minicon show garbled output too. When this happens, I've used cat /dev/ttyUSB0, and the output looks fine. But after some time, having cat /dev/ttyUSB0 running during a reboot, will cause the board to not boot.

william@eee-pc:~$ lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 003: ID 13d3:5071 IMC Networks
Bus 001 Device 006: ID 058f:6335 Alcor Micro Corp. SD/MMC Card Reader
Bus 002 Device 003: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port

Which is actually a PL2303HX,  has worked great on Windows 8 pro, through puTTY, but sometimes does not work properly when connected USB side to a Linux host.

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[William Hermans]

Just as an added aside. When the output from the serial debug cable gets garbled. I do not think this is a problem with the beaglebone hardware. Matter of fact I'm nearly certain.

What seems to be happening is that line feeds are no longer recognized as line feed, and are processes as tabs, or other random control characters. Because text can back up, and over write other text sometimes. Perhaps a call to fflush() needs to be made ?

I wonder if Peter H has any insight on this behavior.

[Graham]

If you are using a USB to RS-232 interface, then you can have problems.

RS-232 is +/- 6 to 12 Volts interface.  -6 to -12 V Negative = Logic 1, +6 to +12 V Positive = Logic 0.  0 Volts is undefined.

The Beagle bone debug connector is 3.3V TTL or CMOS serial interface.

0V => Logic 0, +3.3V => Logic 1.

So, no surprise you are seeing garble.

You need a USB to serial 3.3V interface to talk/listen to the debug interface on the BBB.

--- Graham

==

[evilwulfie]

So how have you not blown up your BBB ?

(1 )  that converter is NOT a 3.3v version

(2)  that sure don't look like a 3.3v serial either

don't blow up your BBB just get a 3.3v serial debug cable

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[softy]

I tried logging using this -> http://www.ebay.in/itm/252048060798?aff_source=Sok-Goog#shpCntId

There is jumper for 3v3 and 5v , i have put it 3v3 and i can see garbled data.Settings are 115200 8N1.

What could be the issue.?