I wrote a I2C library for the Raspberry Pi. It's done via WiringPi library.

I wrote an example how to read out a MPU 6050 accellerometer + gyro. So this would be a good start to learn how to use my I2C library.

The new source code is available on my Nano VM GitHub repo.

Here is the short example program:

//	i2clib.nanoc
//
//	reads i2c port with shared library
//	Stefan Pietzonke 2017

func main ()
	lint null = 0; lint one = 1;
	qint _fd = 0;
	
	lint _dll;
	
	lint _setup;
	lint _writereg8;
	lint _readreg8;
	
	string dllname[256] = "libi2c.so";
	string i2csetup[256] = "i2c_setup";
	string i2cwritereg8[256] = "i2c_writereg8";
	string i2creadreg8[256] = "i2c_readreg8";
	
	int gyroskop_xout;
	int gyroskop_yout;
	int gyroskop_zout;
	
	int accel_xout;
	int accel_yout;
	int accel_zout;
	
	#NESTED_CODE_ON;
	
//	open libi2c.so library in nanovm/lib directory
	lopen (_dll, dllname);	

//	set function handles
	lfunc (_dll, _setup, i2csetup);
	lfunc (_dll, _writereg8, i2cwritereg8);
	lfunc (_dll, _readreg8, i2creadreg8);
	
//	init module MPU 6050
	#ATOMIC;
	pushtostack (&68);
	
	lcall (_dll, _setup);
	get (_fd, >);
	#ATOMIC_END;
	
//	print "_fd: ", _fd; printn one;
	
//	setup MPU 6050
	#ATOMIC;
	pushtostack> (_fd, &6B, 0);
	
	lcall (_dll, _writereg8);
	#ATOMIC_END;
	
	@read_word_2c (_fd, &43);
	get (gyroskop_xout);
	
	@read_word_2c (_fd, &45);
	get (gyroskop_yout);

	@read_word_2c (_fd, &47);
	get (gyroskop_zout);
	

	@read_word_2c (_fd, &3B);
	get (accel_xout);
	
	@read_word_2c (_fd, &3D);
	get (accel_yout);

	@read_word_2c (_fd, &3F);
	get (accel_zout);
	
	
	print "gyroskop"; printn one;
	print "x: ", gyroskop_xout; printn one;
	print "y: ", gyroskop_yout; printn one;
	print "z: ", gyroskop_zout; printn one;
	printn one;
	
	print "accelleration"; printn one;
	print "x: ", accel_xout; printn one;
	print "y: ", accel_yout; printn one;
	print "z: ", accel_zout; printn one;
	printn one;
	printn one;
	
	exit null;
funcend

func read_word_i2c (qint fd, int reg)
	int h;
	int l;
	int value;
	
	#NESTED_CODE_ON;
	
//	print "fd: ", fd; printn 1;
	
	#ATOMIC;
	pushtostack (reg, fd);
	
	lcall (_dll, _readreg8);
	get (h, >);
	#ATOMIC_END;
	
	reg = ++;
	#ATOMIC;
	pushtostack (reg, fd);
	
	lcall (_dll, _readreg8);
	get (l, >);
	#ATOMIC_END;
	
	value = h << 8 + l;
	return (value);
funcend

func read_word_2c (qint fd, int reg)
	int val;
	int f;
	int ret;
	
	@read_word_i2c (fd, reg);
	get (val);
	
	f = val >= &8000;
	if f;
		ret = 65535 - val + 1;
		ret = 0 - ret;
	else;
		ret = val;
	endif;
	
	return (ret);
funcend
	
lab pushtostack;
#ASSEMB
	rts;
#ASSEMB_END