Using one arduino as serial logger to another ardunio

Would it be possible to use one arduino with an sd card and RTC modules to log the output (I guess via Tx/Rx pins or USB) of a second arduino?
why? imagine the case were you use all your pins but Tx/Rx and you still want to log.
is it possible? I've been looking for it but I cannot find something on that direction.
Thx.

You could do that OK but you should look closely at the real need to do so, as it might not be the sort of thing that you would want to show your mother or your friends.

If you really have a shortage of pins, it might make more sense to look into multiplexing pins, better choice of sensors, more intelligent use of the various bus systems available etc. etc. So it may be better to come forth with what you are really doing, or maybe just imagining it.

You don't say which Arduino you have but assuming you have one with 32k, if you get a second Arduino, it might be a good idea to get a Mega. You might then find that you can use that by itself, and reuse whatever you have now for something more sensible.

I think that, with data-logging it is more common to run out of memory before you run out of pins but, if you are really running short of pins, you are probably going to run out of memory very soon anyway - hence the Mega.

is it possible?

Yup. Go ahead and do it. Nothing wrong with it at all.
In fact, I've done it. There weren't enough pins left to have the uSD card as well as everything else, so the Nano which did the logging also had the RTC. When the RTC "ticked" the logger read the ADCs and digital inputs, formed an ASCII string and sent that via serial to the other Nano which wrote the whole thing to the uSD card.

Pete

Thank you for your answers,
Addressing some of @Nick_Pyner comments:
Is not necessarily a pin shortage that brings me here, but it "kind of" is... (I'm using a nano)

If I got it right, the RTC will use the i2c pins, meaning that either I plug my i2c lcd screen, or the rtc. And the sd card needs one of the pwm pins associated to timmer1 and I'm "messing it up" in order to change pwm frequency, and I really don't want to change timer0 (to keep timing functions)...

Also! The logging thing is something I need just to set up some parameters and layer I will not use it anymore... in my case I would like to study the evolution in temperature and current consumption on an electric motor, so I plan to log them for a month and then I can set my thresholds limits to cut power if exceeded.

If I got it right, the RTC will use the i2c pins, meaning that either I plug my i2c lcd screen, or the rtc.

No. I2C is bus, you can have several devices connected. Each one has its own address. Of course, unique address on the bus.

jorgemarmo:
And the sd card needs one of the pwm pins associated to timmer1 and I'm "messing it up" in order to change pwm frequency, and I really don't want to change timer0 (to keep timing functions)...

And what you are trying to do is still far from clear but, if it is the select pin for the SD that is bothering you, that can go somewhere else.

Jack Christensen has done this, it works great!

The RTC would be on the transmitting Arduino.
Then send the data and time to this package for logging.

.