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Topic: can we use RX & TX as gerneral purpose I/O (Read 713 times) previous topic - next topic

dharani

Hi,
   I am usinag Ardunio Duemilanove board. I am trying to set TX & RX pins as input pins. But, if i measure the voltage at RX & TX pins it shows 4.5V always. And if i measure voltage at other pins which shows me 200mV ( This pins also set to input mode). How can use RX & TX as a general purpose I/O.

Grumpy_Mike

Yes you can but it has the output of the serial / USB chip connected to it through a 1K so any input must override that. Plus you have to disconnect it when uploading.

dharani

Hi,
    Even i have disconnected the usb and i am powering the unit using external power supply. Then also i am getting 4.5v at both TX  & RX pins.all other pins gives me 0v or 250mv. Weather i need to do anything on the 1K resistor or any other options.

UKHeliBob

It's time you posted your code I think.
Please do not send me PMs asking for help.  Post in the forum then everyone will benefit from seeing the questions and answers.

Grumpy_Mike

Quote
Then also i am getting 4.5v at both TX  & RX pins.all other pins gives me 0v or 250mv.

Yes you will. The USB / Serial chip is still on the board and is still being powered.

Quote
Weather i need to do anything on the 1K resistor or any other options.

You need to connect it to an input that will drive a 1K pull up load to low for using it as an input.

Nick Gammon


And if i measure voltage at other pins which shows me 200mV ( This pins also set to input mode). How can use RX & TX as a general purpose I/O.


I/O is Input/Output.

Did you have Input in mind, or Output?
http://www.gammon.com.au/electronics


PeterH


TX & RX  as a input pin.


In that case Reply #1 gives you your answer.
I only provide help via the forum - please do not contact me for private consultancy.

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