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Author Topic: TX / RX etc LEDS  (Read 520 times)
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Spain
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Hi,

Is it possible without interfering with the usage of the RX pin etc, to drive an LED from it, so that it extends the SMD leds and can be mounted on an enclosure so that I can see if data transfer is happening etc.
If so, how so? And can all te pins do this?
Any advice gratefully received.
Thanks and kind regards,

jB  smiley-cool
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Any pin can drive an LED provided there's a current limiting resistor to restrict the current to 20mA or less.  For serial lines you need to check the sense of the pin when the signal is idle if you want to ensure the LED is only flickering on during transmission.
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There is an SMD LED on pin 13, you could just put another LED of your liking onto the lid of your enclosure and drive it with logic so that when you send or receive a string it flashes, any pin will do that for you, and yes it is a bit more work but if thats what you need, some of the screw shields come with a pin 13 LED on them, this flashes when the program is loaded but not for TX RX. Pin 13 has a resistor built in i think.
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Yes you can connect an LED.  To prevent interference with the RX functionality I would suggest driving it through a transistor.
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Spain
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Hi,

Thanks for the great responses.

Kind regards,

jB  smiley-cool
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The LEDs on the board are not driven by the TX and RX lines but by the UART / serial interface. You can hang an LED off the TX line on the arduino but because it spends most if its time high you will have to wire it to supply the current by sinking rather than sourcing. This is so you will see it flash on when something is sent. This you will see, where as flashing off when something is sent is virtually invisible.
So TX to a resistor, other end of the resistor to the LED, other end of the LED to +5V.
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