- tx and rx callbacks for each module
 - Callbacks can be called after each read/write cycle or per byte
 - Each I2C module can have different callbacks
 - General call support also working
 - Supports master and slave at same time. Also works with multimaster

Usage:

i2c_msg msg;
char buffer[255];

main()
{
    i2c_slave_enable(I2C1, I2C_FAST_MODE | I2C_SLAVE_DUAL_ADDRESS | I2C_SLAVE_GENERAL_CALL | I2C_SLAVE_USE_RX_BUFFER); // init slave mode. Enables master too
    i2c_slave_attach_recv_handler(I2C1, pmsg, funcrx); // attach  receive handler
    i2c_slave_attach_transmit_handler(I2C1, pmsg, functx);   // attach transmit handler
    i2c_slave_set_own_address(I2C1, 0x10);    // set addresss 1
    i2c_slave_set_own_address2(I2C1, 0x20);   // set addresss 2
}

void funcrx(i2c_msg *msg)
{
    printf("length is %d.\n", msg->length);
    char return_data = msg0>data[0];
}

void functx(i2c_msg *dev)
{
    msg->data[0] = 0x01;
    msg->data[1] = 0x02;
    msg->data[2] = 0x03;
    msg->data[3] = 0x04;
    msg->data[4] = 0x05;
    msg->length = 5;
}

All code derived from datasheets and libmaple.
Signed-off-by:- Barry Carter <barry.carter@gmail.com>
I2C slave support cleanups.

Added fix for corner case where badly behaving master doesn't NACK and we don't get the callbacks fires.

Removed my own name from several places and added attribution to the correct place.

Updated include comments to reference the fact it now supports I2C slave

Signed-off-by:- Barry Carter <barry.carter@gmail.com>
Added I2C slave echo example in examples folder. Using another maple, write a byte and then read.
Slight tidy up.
Reformatted CREDITS file to be in correct order.
Added a note about buffer overrun

Signed-off-by:- Barry Carter <barry.carter@gmail.com>
libmaple/timer.c: Sync enable_irq() declaration with it's definition

Signed-off-by: Daniel Nyström <daniel@nystrom.st>
wirish/syscalls.c: Replace obsolete caddr_t with void *

caddr_t is obsolete in POSIX and thus unavailable in most modern
toolchains. caddr_t usage should be replaced by void *.

stddef.h includes the size_t typedef which was missing.

Signed-off-by: Daniel Nyström <daniel@nystrom.st>
build-rules.mk: Add CROSS_COMPILE env var support

Since toolchains other then older Code Sourcery (Mentor Graphics)
might not use the arm-none-eabi triplet, make it possible to use
any triplet by just setting the CROSS_COMPILE environment variable
accordingly.

Signed-off-by: Daniel Nyström <daniel@nystrom.st>
Merge pull request #54 from ginge/master

Added i2c slave support