README

Raduino
=======
A C based programming with Arduino look alike syntax for
Raspberry Pi. This are simple baremetal programming
libraries like Arduino for Raspberry Pi 2. Yes we can use direct
C++ instead of this for development, but it is done in C because
to have fun with all macro magic and linker (actually I do not know
C++ :)). This is in very initial stage with GPIO, Serial and String
libraries (not fully implemented).
Lets see how Arduino code and Raduino code looks:

Arduino:
++++++++

void setup()
{
	pinMode(13, OUTPUT);
	Serial.begin(115200);
}

void loop()
{
		digitalWrite(13, HIGH);
		Serial.println("Get lost..You suck at coding");
		delay(1000);
		digitalWrite(13, LOW);
		delay(1000);
}

Raduino:
++++++++

#define "gpio.h"
#define "uart.h"

OBJECT(Serial, s1);

void setup()
{
	pinMode(13, OUTPUT);
	s1.begin(115200);
}

void loop()
{
		digitalWrite(13, HIGH);
		/* using printf as of now */
		s1.printf("Get lost..You suck at coding\r\n");
		delay(); /* delay() is close to 1 sec as of now */
		digitalWrite(13, LOW);
		delay();
}

How it works:
-------------

-> Initial assembly code which is run at start is changed to call setup()
	function once and call loop() infinitely.
-> Before calling setup() C run time environment is setup:
	- Stack pointer setup
	- c_startup function(in startup.c) clears BSS and initializes objects
	  for a class. Let us take a closer look at Classes and Objects here.
		The macros OBJECT and CLASS(used by library code) expands such that
		s1 gets placed in objects section, Serial has Serial_name structure
		(internally) variable which gets placed in classes section in memory.
		Each Class and Object are placed such that they are aligned to 4 byte
		boundary. This alignment is used to get to next Class/Object variable in
		memory.
			next_class  = roundup(class_start + sizeof(Class), ALIGNMENT);
			next_object = roundup(obj_start + obj->size, ALIGNMENT);
		One Class variable is taken and initialization function of all objects
		for that Class are called. This is process repeated for all Classes.
		If application uses like below:
			OBJECT(Serial, ser); 
			OBJECT(String, s1);
		then ser is checked if it belongs to Serial or String(name comparison)
		and if yes intialization function of ser is called(which initializes its
		members). Have a look at startup.c, object.h, uart.c and string.h for
		understanding.

So to write a new module/component(whatever you call) all you just to need
to do is declare you structure(say Lcd) in a header file,

typedef struct
{
	Object obj; /* this is required and do not touch it */

	/* your variables and routines */
	void (*begin)(void);
} Lcd;

and in C file,

static void lcd_begin(void)
{
	/* your code for lcd initialization */
}

static void Lcd_init(void *object)
{
		Lcd *lcd = object;

		lcd->begin = lcd_begin;
}

CLASS(Lcd, Lcd_init);

in application user can use:
OBJECT(Lcd, lcd);

and call Lcd.begin();

Pitfalls
--------

OBJECTs cannot be used as local variables.
Calling functions with different type of arguments is not possible.
Functions has to be called with structure variable pointer(eg: String).

This is intial effort and I will keep updating to make it more like Arduino
program.

Credits
-------
I have to thank all the guys who spent time in writing blogs and 
bare metal code for Raspberry Pi and ARM processor.
	David Welch (https://github.com/dwelch67/raspberrypi)
	Brian_S (http://www.valvers.com/open-software/raspberry-pi)
	Kustaa Nyholm /SpareTimeLabs (printf function is taken from Kustaa Nyholm
									as of now)
			http://www.sparetimelabs.com/tinyprintf/tinyprintf.php

I am really looking forward for others to contribute for rest of the peripherals
if interested :).

Thanks,
Sundeep