ti_chris
Posts: 3
Joined: Sun Feb 07, 2016 12:44 pm

Serial loopback not working with new build

Fri Aug 10, 2018 5:22 am

I'm trying to setup my alarmdecoder with the latest build (It all used to work with Jessie) and I'm running into some issues just getting the serial port to work now (let alone the alarmdecoder) :(.

Thus I've done a simple test. I've disconnected the alarmdecoder from Rx/Tx and I've shorted Rx and Tx (BCM GPIO14 & 15) with a wire. Then I loaded

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minicom  -b 115200 -o -D /dev/serial0
and tried typing only to find out that nothing echo'ed after disabling hardware flow control. PS: I ran minicom as root to circumvent any potential issue regarding permissions.

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    +-----------------------------------------------------------------------+
    | A -    Serial Device      : /dev/ttyAMA0                              |
    | B - Lockfile Location     : /var/lock                                 |
    | C -   Callin Program      :                                           |
    | D -  Callout Program      :                                           |
    | E -    Bps/Par/Bits       : 115200 8N1                                |
    | F - Hardware Flow Control : No                                        |
    | G - Software Flow Control : No                                        |
    |                                                                       |
    |    Change which setting?                                              |
    +-----------------------------------------------------------------------+
My OS is (cat /proc/version):

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Linux version 4.14.34+ ([email protected]) (gcc version 4.9.3 (crosstool-NG crosstool-ng-1.22.0-88-g8460611)) #1110 Mon Apr 16 14:51:42 BST 2018
My config.txt file (cat /boot/config.txt | grep uart):

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#dtoverlay=pi3-miniuart-bt
enable_uart=1
My cmdline.txt (cat /boot/cmdline.txt)

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dwc_otg.lpm_enable=0 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait
Looking for getty using it (ps aux | grep getty)

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root       712  0.0  0.3   4040  1744 tty1     Ss+  21:33   0:00 /sbin/agetty --noclear tty1 linux
pi        1568  0.0  0.4   4272  2096 pts/0    S+   22:05   0:00 grep --color=auto getty
Looking for other processes using AMA0 (ps aux | grep ttyAMA0)

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root      1606  1.0  0.3   4268  1888 pts/0    S+   22:08   0:00 grep ttyAMA0
Permission on device blocks:

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lrwxrwxrwx 1 root root 7 Aug  9 21:28 serial0 -> ttyAMA0
crw-rw---- 1 root dialout 204, 64 Aug  9 22:14 ttyAMA0
At this point I'm running at a loss as to what could possibly be going wrong. Any idea? I've tried this on a Raspberry Pi Zero as well as an older raspberry pi B (rev 2.0) with no luck. I'd appreciate any ideas/pointers at this point.

Thanks,
Chris

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