Uart isn't working


13 posts
by marun » Fri Feb 22, 2013 2:18 pm
hi
Uart was working until i rewrited card with new version of raspbian .img because i accidentally uninstalled important packages
i reconfigured UART by this page http://www.raspberry-projects.com/pi/programming-in-c/uart-serial-port/using-the-uart but GPIO14 is always low now i tried to connect it through 100k resistor on 5V and there was 5V it doesn't look like i burnt it out
do you know where could be a mistake?

my old vresion of linux was 3.2.27+
my new is 3.6.11+ (report from nbench)


oh no i pulled it to 5v is there an possibility to burn it out with 50uA?
Last edited by marun on Sat Mar 09, 2013 11:57 am, edited 1 time in total.
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by marun » Sat Feb 23, 2013 11:17 am
i tried to reinstall card and it still doesn't work
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by klricks » Sat Feb 23, 2013 3:01 pm
I am also having some trouble with latest release of Raspbian 2013-02-09
I have been using 2 programs CuteCom and minicom.

Minicom (text based) works fine for both RX (data in) and TX (data out) . However CuteCom (GUI based) has trouble with TX to my serial device. It does work sporadically from time to time. If I close and reopen the port via the CuteCom console then TX may work a few times then stop.

When I swap in my SD card with older image everything works perfectly.

See my web page on how I set up and configured the serial port:

http://64.13.91.137:86/Comp/RPi/Rpi.html
Go here for my RPi writeup. Basic config, Serial Port add-on etc:
http://home.budget.net/~klricks/Comp/RPi/Rpi.html
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by marun » Sun Feb 24, 2013 7:24 am
can you please upload somewhere your old card image? (just do dd but with swapped if and of)
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by klricks » Sun Feb 24, 2013 2:57 pm
marun wrote:can you please upload somewhere your old card image? (just do dd but with swapped if and of)



See is this works
http://downloads.raspberrypi.org/download.php?file=/images/raspbian/2012-10-28-wheezy-raspbian/2012-10-28-wheezy-raspbian.zip

Couldn't find a direct link for older images so I reconstructed the above URL by going to the current download link... cancel download....then edit the URL in my browser using the dates of the older image. If that is not the image you had then try with the dates (file-name) from your old image.

My upload speed is really slow (256kb) and it would take a long long time to upload even the zipped image. My ISP tends to throttle as well.
Go here for my RPi writeup. Basic config, Serial Port add-on etc:
http://home.budget.net/~klricks/Comp/RPi/Rpi.html
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by rew » Sun Feb 24, 2013 3:58 pm
marun wrote:oh no i pulled it to 5v is there an possibility to burn it out with 50uA?
No, not really.

The specifications of most chips say the voltage on the input pins should not exceed the power rails by more than 0.3V. This is because there is a low-forward-drop diode from the pin to the power rails. It might start conducting anywhere between 0.3 and 0.6V.

However this diode could simply handle a certain current. They should also specify a maximum current.

A motor-driver-manufacturer (maybe ST) "discovered" this. So now they specify the maximum current. If I remember correctly the maximum current that the diode can handle indefinitely is about 10mA. To be safe, stay under 1mA. Or even safer under 0.1mA, as you did.

Officially you are exceeding specs (because everybody still just specifies max voltage), but in practise you won't kill the chip with a small current.
Check out our raspberry pi addons: http://www.bitwizard.nl/catalog/
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by klricks » Thu Feb 28, 2013 1:42 pm
klricks wrote:I am also having some trouble with latest release of Raspbian 2013-02-09
I have been using 2 programs CuteCom and minicom.

Minicom (text based) works fine for both RX (data in) and TX (data out) . However CuteCom (GUI based) has trouble with TX to my serial device. It does work sporadically from time to time. If I close and reopen the port via the CuteCom console then TX may work a few times then stop.

When I swap in my SD card with older image everything works perfectly.

See my web page on how I set up and configured the serial port:

http://64.13.91.137:86/Comp/RPi/Rpi.html


I found that with the newer image, TX and RX both work fine if I start Cutecom from the command line with sudo cutecom rather than starting from the screen menu icon.
Go here for my RPi writeup. Basic config, Serial Port add-on etc:
http://home.budget.net/~klricks/Comp/RPi/Rpi.html
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Location: Grants Pass, OR, USA
by marun » Fri Mar 01, 2013 8:36 am
ok thanks
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by marun » Fri Mar 08, 2013 6:07 pm
i found this link http://downloads.raspberrypi.org/images/raspbian/ here are all raspbian images
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by marun » Fri Mar 08, 2013 7:21 pm
i installed older image but same problem i think it isn't problem of images


i installed other old image but same problem

i think there is different problem
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by marun » Sat Mar 09, 2013 11:24 am
klricks wrote:
klricks wrote:I am also having some trouble with latest release of Raspbian 2013-02-09
I have been using 2 programs CuteCom and minicom.

Minicom (text based) works fine for both RX (data in) and TX (data out) . However CuteCom (GUI based) has trouble with TX to my serial device. It does work sporadically from time to time. If I close and reopen the port via the CuteCom console then TX may work a few times then stop.

When I swap in my SD card with older image everything works perfectly.

See my web page on how I set up and configured the serial port:

http://64.13.91.137:86/Comp/RPi/Rpi.html


I found that with the newer image, TX and RX both work fine if I start Cutecom from the command line with sudo cutecom rather than starting from the screen menu icon.


no even if i download the newest image and do dist-upgrade and type sudo cutecom it doesn't work

i need it for my school project and on monday 18th we have presentation but if it won't work my 2 month work can go to bin
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by marun » Mon Mar 11, 2013 4:38 pm
i can't belive it
i burned my ttyAMA0 gpio pins
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by GreenSB » Wed Apr 17, 2013 12:05 am
Do this and I think you will get ttyAMA0 to work:
/boot/cmdline.txt : delete -> console=ttyAMA0,115200 kgdboc=ttyAMA0,115200
save it

/etc/inittab: ctrl w type ttyAMA0, put # in front of that rowe
save it

reboot your pi

http://www.raspberry-projects.com/pi/programming-in-c/uart-serial-port/using-the-uart
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