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Author Topic: TX works after uploading sketch, but doesn't work after loosing power  (Read 397 times)
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Not sure if this is the right section or not, but I'm experiencing something weird with TX.  For some reason it'll work right after I upload my sketch, but as soon as I unplug my arduino uno and then plug in back into the computer it does work. I know it's not working because the TX LED doesn't light up.  Everything else works fine. 

Does anyone have any idea what's going on?
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I know it's not working because the TX LED doesn't light up.

That in itself isn't an indication of anything being wrong. Just plugging in the arduino doesn't mean there is any application in the PC ready to communicate with it. Test with a sketch and the IDE serial monitor.

Lefty

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I know it's not working because the TX LED doesn't light up.

The Uno's TX light won't flash unless something opens the serial port.  Flash Pin 13 if you want to verify when your program starts running.
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Unplugging and plugging in too quickly can fool a windows system into not opening or registering it as a port. It might also change the port number, so your recieving program is looking at the wrong place. The TX and RX lights are controlled by the PC's driver not by the sign els generated bynthe arduino and is an indication that the PC is not seeing it as a port.
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@retrolefty, I'm using a LCD to monitor my sketch, so I know is working, it's just not send commands via the serial port.

@James C4S, how do I open the open the serial port?

@Grumpy_Mike, ok, now I'm confused.  Are you guys saying the only what I can use the the arduino serial ports is if it's connected to a PC?  Oh and I'm on a Mac.
« Last Edit: June 30, 2011, 09:31:04 pm by JRMN » Logged

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"open the serial port"

I meant, the Uno won't flash the TX light unless something on the computer side "opens" the serial device.

FYI, I'm on a Mac too.
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Are you guys saying the only what I can use the the arduino serial ports is if it's connected to a PC?
No I am saying that is the only time the TX and RX LEDs flash. These LEDs just look like GPIO to the USB drivers and it is the PC (or Mac ) that does the flashing of them.
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