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Author Topic: RX / TX Lights constantly on with external power  (Read 1466 times)
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Hi,

Upon my first time connecting external power to the Arduino, I noticed that the RX and TX leds are dimly lit all the time the power is connected. This is not the case when powering through USB.

My adapter is a 9V DC 1A center positive one.

Is this normal?

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I just tried executing a program that works when the Arduino is powered via USB; it didn't work, so I immediately disconnected the adapter.

What could be wrong here?
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hi

can you explain it a bit more? Everything works on USB, but not on battery?

D
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Everything works when the Arduino is powered via USB, but nothing works (only the PWR led is lit as normal, and the TX and RX leds are constantly lit very dimly) when the DC power supply is connected.
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Check the first question here.  I'm guessing that is your issue.
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Thanks; it indeed was.

Does everyone using an external power source experience this? In other words, is it a known and confirmed "bug"?

Another question: Would it hurt to keep RX and TX connected to each other all the time I don't use them, to work around this?
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Thanks; it indeed was.

Does everyone using an external power source experience this? In other words, is it a known and confirmed "bug"?

Another question: Would it hurt to keep RX and TX connected to each other all the time I don't use them, to work around this?

yes it's a confirmed bug, and no, that would be a bad idea to connect them together, as you would possibly damage both the USB chip and the Atmega, since when the Atmega TX is low the USB TX could drive current into it, and vice-versa  smiley

D
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In fact, it should be fixed in the Diecimila, or (maybe) if you burn the revised NG bootloader included in Arduino 0009.
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I haven't tried 0009 so far, since there's no Linux release, and I've been reluctant to compile from CVS. I'll take a look now.

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that would be a bad idea to connect them together, as you would possibly damage both the USB chip and the Atmega, since when the Atmega TX is low the USB TX could drive current into it, and vice-versa

If that's the case, http://www.arduino.cc/en/Guide/Troubleshooting is giving dangerous advice; the part that recommends connecting RX and TX together should be edited out.

So is connecting RX to one of the GND pins on the Arduino via a resistor the safest thing to do?

« Last Edit: August 09, 2007, 06:53:06 pm by 23 » Logged

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Hi,
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I haven't tried 0009 so far, since there's no Linux release, and I've been reluctant to compile from CVS. I'll take a look now.
The Linux version is available since the day before yesterday : see http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1186451401

Have fun
Eberhard
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Thanks for the heads up. Is there a way to burn the new bootloader to the NG via USB?
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