Basics of C++ with Arduino

Question

I have read about Arduino, and how it uses a language that is similar but not equal to C. I am very familiar with C++, and I was wondering how one would do basic tasks with the Arduino, such as communicating with the I/O pins. I figure that one would need the memory address to the pins, and then do something like this for a "flashing led":

int main()    {
    while (1)    {
        bool * out_pin = /* Whatever that memory address was for that pin */;
        *out_pin = 1;
        // Some sort of sleep function? (I only know of "windows.h"'s "Sleep" function)
        *out_pin = 0;
    }
    return 0; // Kind of unneeded, I suppose, but probably compiler errors otherwise.
}

I'm probably really wrong: that's why I'm asking this question.

Close. The pins don't have memory addresses (they're register mapped, not memory mapped). Generally, the compiler already maps them to variables for you. So you just do pin_name = pin_value; (like PORTD = 7;) and the compiler does the magic. — David Schwartz
– David Schwartz, Commented Jul 30, 2012 at 1:08
Thank you so much for that (quick!) answer. I am curious this though: what type is your "pin_name" Is it a bool * or something else? And can you later do what I did modifying the value (and such)? — Cosine
– Cosine, Commented Jul 30, 2012 at 1:13
It's a keyword for a register. It behaves like a variable. When the compiler sees PORTD = 7; is compiles it to the necessary assembly code to load a 7 into the PORTD register. When it sees i = PORTD; is loads the value from the PORTD register and stored it in the variable i. The compiler just makes it work. — David Schwartz
– David Schwartz, Commented Jul 30, 2012 at 1:14
Your use of web-searches seems to be failing, one of the first examples on the official Arduino page is a blinking led. — Some programmer dude
– Some programmer dude, Commented Jul 30, 2012 at 5:50
@Joachim: That is in the Arduino language: I figured it was different with C++, even with the Arduino library. I searched the web far before asking this question. It has been answered already. (But I can't mark it as answered until two days after asking it). — Cosine
– Cosine, Commented Jul 30, 2012 at 15:17

Cosine · Accepted Answer · 2012-07-30 01:18:57Z

1

This is copied from the comments below my question. David Schwartz answered my questions:

Close. The pins don't have memory addresses (they're register mapped, not memory mapped). Generally, the compiler already maps them to variables for you. So you just do pin_name = pin_value; (like PORTD = 7;) and the compiler does the magic. – David Schwartz 7 mins ago

[PORTD's] a keyword for a register. It behaves like a variable. When the compiler sees PORTD = 7; is compiles it to the necessary assembly code to load a 7 into the PORTD register. When it sees i = PORTD; is loads the value from the PORTD register and stored it in the variable i. The compiler just makes it work. – David Schwartz 2 mins ago

Thank you!

answered Jul 30, 2012 at 1:18

Cosine

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Comments

Arnab Datta · Accepted Answer · 2012-07-30 01:08:08Z

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You need to use pinMode(your_pin) to activate the IO pin. Then you can use digital/analog write/read to communicate with them

answered Jul 30, 2012 at 1:08

Arnab Datta

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2 Comments

Cosine Over a year ago

What library is pinMode in? I thought that that was an "Arduino Programming Language" function. Is there a library where I can get that for C++?

Arnab Datta Over a year ago

pinMode is indeed in the arduino standard library. I haven't heard of a pure C++ equivalent

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