Accessing the serial console

[samuel...@maine.edu]

Good afternoon, I have spent the better part of a week attempting to get access to the uboot serial console on the GK-802, but with no success.

Here is my situation, I have three of the six pins (UART Txd, Rxd, and GND) connected to a serial cable which is then connected into a machine running Ubuntu 14.04 desktop. I have been using minicom to view the output of the serial port, and while data comes over the connection, it is completely garbled.

Here is an excerpt:
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                        ��[5 5 �9= 5��_a[��{!=��eO�]�1)���w[}e�����q-{��YY^����e�eݽ�-~���sYgAYwoy����������� j ��+������m��~ -#1�753= ' �5# - !#%5# ����1! �%!75����������坝������=9 - 5� -5' �� -5'�9'!9)������� ��5#=;'5A/7%-�� 5 �owem�%!#- ! ��W)�t�j��{ݕ��^��������[������T���:Z�a ���� 5 -='��u � !� ! �= !;!! �������YY^�
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5�������:���� �+                  57�3-'5
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5�������:���� �+                  57�3-'5
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i used stty -F <serial_device> and setserial <serial_device> to set the baud rate to 115200 and 8N1 with no hardware or software flow control.

Any suggestions as to how I might correct this would be much appreciated!

[Žydrūnas Urbonas]

I sometimes get similar crap too. Then I check serial pins if they sit solid, turn on/off gk802 few times until serial works. Not sure why this happens

[samuel...@maine.edu]

Yeah I don't know, I think my issue is that I was attempting to use an RS-232 cable (the TxD, RxD, and signal ground) wires) instead of the TTL to USB board. I bought one and hopefully it fixes the issue. Thank you so much for the help!

[Dmitriy B.]

2014-07-01 0:19 GMT+04:00 <samuel...@maine.edu>:

Yeah I don't know, I think my issue is that I was attempting to use an RS-232 cable

Usage of RS232 levels cable can easily damage UART port on i.MX6. Nearly all current generation SoC chips are not compatible with RS232 without convertors like Maxim MAX3323 (http://datasheets.maximintegrated.com/en/ds/MAX3322E-MAX3323E.pdf).

Best Regards,

Dmitriy Beykun

[samuel...@maine.edu]

Oh ok thank you for that information. It is very helpful!

Samuel Barton

[Žydrūnas Urbonas]

I also have just noticed, if you accidentally connect pins wrong, Tx-Tx and Rx-Rx - you will get same garbage in your console

Make sure you connect your TTL as Tx-Rx and Rx-Tx

[samuel...@maine.edu]

thank you all for your information, the board came and the serial console output is now English! :)