I need one more pin

As you can see from my current pinout diagram, I am using all of the Digital and Analog pins. I need one more pin for a relay module. Can any of the remaining open pins be used?

Just a guess, but if you don't need serial comms in your sketch, then you could use the TXD pin as an output.

I think you would need to be able to disconnect whatever is connected to TXD in order to upload a sketch.

@markd833 Which pin is the TDX pin?

Which pin is marked with a "T" and an "X"?

Also, what are your pins used for? You assume that there is no way to release any of them?

Looks like it's marked TX1 on the board in the picture - top right hand corner. It'll be D0 in your code when you use it as an output.

D2-D9 are going to an 8 channel relay module
D10-D13 are going to an SD module
A0-A2 are going to momentary push buttons
A4-A5 are going to an I2C LCD display
A3, A6, and A7 are going to 3 channels of a 4 channel relay module. I would like to use the fourth channel.

@tharnden7 you posted in the wrong section. Moved it here.

How possible? A6 and A7 don't have digital I/O capability.

Those two pins can't be outputs.

So just use A0 with a resistor network and an analog read and you have two pins spare.

Demonstrating why the forum guidelines strongly suggest you post all the information about your project...

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I just picked up an arduino for the first time about 1 month ago. Let's just assume I don't know what I am talking about and treat me like a 5 year old.

Use an I2C IO expander like the MCP23008. Will give you 8 more IO pins and not use any pins (I2C is a bus and the LCD is already there). Then you have the pins for the relay module plus a few extra.

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I read in another forum that the A pins can be used like the D pins. I currently have my 8 channel relay module hooked up and it is working great. I am waiting for my 4 channel relay module to come in the mail and then I would have discovered that A6 and A7 would not work.

That's why you should read the available online documentation instead of relying on forum posts for information... those pins are fully documented on the Arduino Nano product page.

This sounds great but I would have no idea how to integrate this into my design.

Correct but A6 and A7 are special exceptions.

...that we haven't seen yet...

Your assuming I haven't read the documentation. Again, I am very new to this and much of the terminology goes over my head.

You must show us your design. Diagrams and/or images of the hardware and wiring. All of it, not just the Nano.

I'm not assuming that you haven't read the documentation. You failed to mention it. You only referred to forum posts. What you tell me, is all I know...

They can on an Arduino Uno because while A6 and A7 are inside the chip in the dual in line package these pins are not brought out. So in an other package like the surface mount one in the NANO you get these pins but there are restrictions on them.

A lot to learn and the devil is in the detail.