Need some advices...

Hi, I'm Italian so, sorry for my bad English. I have to buy an Arduino, but I heard about Arduino UNO R3 and Arduino Mega. If I'm not wrong, Mega has more pins than UNO. I have to build a small project: I want to use this http://www.ladyada.net/products/tfttouchbreakout/ screen, this microsd card reader http://www.robot-italy.com/it/microsd-shield.html, this printer https://www.adafruit.com/products/600, 12 buttons (or more... I'll see), and, if I find something else, I'd like to add it to the project (maybe some sensors). Oh, I forgot: I want to use an rgb led too. I've never used Arduino, but I want to buy an Arduino for either learning and this project. When I finished to use it for learning purposes, I want to build a very very small computer and I don't want to buy an Arduino uno discovering later that it hasn't got enough pins for my project.

My question is: is an Arduino uno equal to arduino mega except for the number of digital/analogic pins? If I buy an arduino uno, is there a simple mode to extend the number of pins or it is better to buy an arduino mega?

Another question: I read some tutorials that use the same pin for an Led (13). Is it compulsory to use the pin number that it says in the tutorial or can I change it (not the type -digital/analogic-, only the number). if I would connect the led in pin... 10, what it would happen?

Thanks a lot for your patience and for your answers...

Bye and have a good weekend!!!

Jymmy097

With an UNO you have 20 GPIO at most, so given all the stuff you want to connect, you probably better go with a Mega2560. There you not only have more pins but also more RAM (8kB instead of 2kB) and more flash memory (for your programs, 128kB instead of 32kB). Given the low price of an UNO you may first buy an UNO to experiment with (in the beginning the chance to fry a board is certainly higher) and move to the bigger board later.

Actually, 256K of Flash memory on the Mega2560. I think 54 IO pins.
Uno is good to start, the code you develop is easily transported to the Mega, in most cases the only change is to select the Mega in the IDE instead of the Uno, and then add code for any new IO used (such as Serial1.begin() if another serial port is used).

Thanks for your replies. I don't want to buy two arduino boards, so, if there are no differences (except for few things that, as a beginner, I can sove by myself), I'd prefer to buy the Mega. other questions: if I have to connect to mega more pins that it has onboard (so I have to connect to arduino a lot of shields - because I'd like to add some shields in next time...), there is a method to add these pins? Can I increase the Ram of mega with a microsd or something else?

Thanks a lot!!

RuggedCircuits.com offers SRAM shields that can be attached.
I offer a screw shield for the Mega to connect off board parts.
And you can stack other shields on top of course, need to keep track of which pins are used by the shields to avoid conflicts.

I read some tutorials that use the same pin for an Led (13). Is it compulsory to use the pin number that it says in the tutorial or can I change it (not the type -digital/analogic-, only the number). if I would connect the led in pin... 10, what it would happen?

The tutorials use pin 13 for convenience: pin 13 has an led wired in and attached to the board, so using pin 13 means you don't have to bother attaching an external led. You can attach an led to one of the other pins, for sure, or indeed many of them at once. Just remember to use the right number/s in the code, and attach the led with a resistor in series to limit the current.

JimboZA:
The tutorials use pin 13 for convenience: pin 13 has an led wired in and attached to the board, so using pin 13 means you don’t have to bother attaching an external led. You can attach an led to one of the other pins, for sure, or indeed many of them at once. Just remember to use the right number/s in the code, and attach the led with a resistor in series to limit the current.

To add to what JimboZA said, some chips that are programmed the same way as Arduinos, might have the default led on a different pin (for example, digispark only has 6 pins, and there are 2 varients, one with the led on pin 1 and one with the led on pin 0).

Also note that on the Uno, if you want to use SPI communication to talk to intelligent devices, the Uno uses pins 10-13 for the SPI communication. The Mega2560 uses pins 50-53, and the Leonardo doesn’t connect the SPI pins to digital pins. So, if you are on the Unfo, you might not able to use pin 13 if you are using SPI.

Thanks a lot. I'll buy a mega and if I'm in trouble, I'll write on this forum. Bye!!