How to debug linux boot process


#1

Hi,

I’m experimenting with different yocto built images.
Sometimes Linux not booting, and I want to know why.

How can I examine boot messages?
I tried to connect to DB9 connector, with different baud settings, no output was visible.

Regards
Arek


#2

You should connect to the DB9 connector with 115200 8N1.


#3

Thank you for your reply dfrey,

Unfortunately still nothing is visible on the terminal.

Here are some facts:

  • RS232 cable was checked, and working properly.
  • Linux flashed on WP85 is working. I can ssh into.
  • I’m able to flash the device using swiflash utility.
  • I’m able to flash the device using fastboot. But for some reason, Linux is not starting this way.

Regards
Arek


#4

Please try to download latest firmware here:
http://source.sierrawireless.com/resources/legato/wpfirmwarerelease/

It’s a simple one click tool.
Let’s see if that makes any difference


#5

Thank for your reply asyal,

I downloaded newest generic-firmware, boot-yocto, legato and MCU packages.
Flashed using swiflash. Utility reported success for all operations.

Unfortunately that did not help. Still no output on DB9.

I’m suspecting hardware problem.


#6

Yes, could be.
Can you ssh via USB?


#7

Yes, I can ssh.
I’m working on Ubuntu 16.04.
After connecting Mango0h to USB port, new ethernet device is visible and working.


#8

Hi,
you may try to change the uart as Linux console using AT command. It may work.
Here is the steps:

ssh to device

microcom -E /dev/ttyAT

AT!MAPUART=16,2 (uart 2 as Linux Console )
AT!MAPUART=16,1 (uart 1 as Linux Console )

then restart

Thanks


#9

Thank you all for your help.
Finally, I solved my problem.

First, I replaced WP8548 chip. I’ve got a new one, which works. Finally I saw some data produced by serial port.

Second, my cheap RS232/USB converter fails on 115200 baud. All I saw on terminal was white spaces.
Decent converter based on FTDI chip works much better.

Thanks


#10

Thx for letting us know


#11

my cheap RS232/USB converter fails on 115200 baud

If you know the make and model or chipset of the non-working RS232 adapter, then please post it to help others diagnose this problem in the future.


#12

I’ve tried two “cheap” converters.

The black one, recognized by system as:
Bus 001 Device 010: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port

Sometimes received data are corrupted (random characters). Converter is unable to send valid data.


The blue one, recognized by system as:
Bus 001 Device 009: ID 1a86:7523 QinHeng Electronics HL-340 USB-Serial adapter

This one is unusable. Receives random sequence of spaces, tabs, and line feed characters.


Both converters works fine using 9600 baud.


#13

I have two that look like your second one. One wont work at all and teh other comes up as a prolific. Unfortunately the Windows driver has frozen it out presumably because it is not a genuine chip inside. Using an older version of the driver works fine though.

Kas


#14

I am using the blue one (PL2303-Prolific) as well and from what I found from the net, there is issue with driver. I am not able to make it work on windows. However it works well on Ubuntu 16.04, here are the instructions:

  1. connect the serial adaptor to usb port of the Ubuntu machine.
  2. install minicom in linux machine:

sudo apt-get install minicom

  1. find the usb port that serial connect to:

dmesg | grep pl2303

  1. the output of step3 would indicate which usb port

[ 6.804403] usb 1-1.3: pl2303 converter now attached to ttyUSB0

  1. change file permission to allow minicom to save config using ttyUSB0 as an example

sudo chmod 755 /dev/ttyUSB0
6.run minicom
mnicom -s

  1. from the config menu, select “Serial port setup”.
  2. press “A”; update A-Serial Device: to what you see in step4. It would look like
    A-Serial Device: /dev/ttyUSB0
  3. hit “enter” and then press “E” to select “E-bps/par/Bits: 115200 8N1”
  4. hit “enter” and select “save setup as dfl” and select “Exit”

If everything goes well, you will see
"Welcome to minicom 2.7
Port /dev/ttyUSB1"

type your user name and password to login to your mangOH board.


WP8548 stuck in init process
#15

For the UART converters, most of the cheap one are very unreliable and will waste your time (fake Prolific chips, …)

I’ve been using the Trendnet TU-S9 for about 10 years and never had any issue with them, cf https://www.trendnet.com/products/proddetail?prod=150_TU-S9 . They cost about 15 bucks, so about 3 times the price of something that works a third of the time … :stuck_out_tongue: