Hello, I am trying to understand what the pins on the Mega do. I guess I can tell by reading the 3rd column (Mapped Pin Name) of the following table. Am I correct?
I noticed that quite a lot of digital pins have a parenthesis behind it. Does that mean that particular pin can serve two functions? Do I need to do anything to tell Arduino which function I choose? Is the name before the parenthesis the default use?
What do the following mean and what is the use?
Digital pin 15 (RX3) and pin 14 (TX3): Seems to be one of the four pairs of hardware serial ports. How can I tell arduino if these pins are for digital I/O or serve as serial ports? Is the default digital I/O rather than hardware serial ports? Is there an ordering on serial ports? For example, I have to use RX1-TX1 before I can use RX2-TX2, etc.
Digital pin (PWM): Does that mean the pin can generate PWM signal or just discontinuous 0/1. It can also accept digital signal?
Analog Reference
Some pins have no name. For example, rows 4, 8, 9, 27-29, 47-49, 65-69, 79 in the table. Am I supposed not to insert anything into these pins?
I suggest that you download the schematic diagram. You will see that the pins that have no name in the 'mapped pin name' column are not use in the schematic; this means that they are not available on the headers and that you can only connect something there by directly soldering wires to the micro
The 'pin number' column contains the numbers of the pins of the 2560 micro (not the board).
The 'pin name' column contains the names as used by Atmel in their datasheet of the 2560 micro; find it and download it. The names between parenthesis indicate the so-called alternate functions. E.g. pin number 1 on the 2560 micro can be used as a general purpose IO (pin 4 on the Mega board) or as a PWM output on the same pin 4.
The pins 2 and 3 of the 2560 micro are mapped to the pins marked 0 and 1 on the Mega board; so look at the headers on the board to find them (note; that on the board they might only have the alternate name; not sure as I don't have a ME=ega). Their alternate functions are RX0 and TX0. So you can use it either as digital pins or for serial communication. Using those as general purpose IO pins might be a bit tricky because those pins are also connected to the 16U2 micro for USB communication.