libi2c

Linux userspace i2c library.

Features

• Support C/C++ and Python.

• Support Python2+, Python3+

• Support multiple bus and devices.

• Support 7-bit and 10-bit i2c slave address.

• Support 1 - 4 byte internal address, auto convert.

• Provide read/write/ioctl functions to operate i2c device.

• Support 8/16/32/64/128/256 bytes page aligned write, read/write length are unlimited.

• Using ioctl functions operate i2c can ignore i2c device ack signal and internal address.

Installation

pip install pylibi2c

or

sudo python setup.py install

or

sudo make install

or

sudo make install PYTHON=pythonX.X

Interface

i2c_ioctl_write (once max 16 bytes) are more efficient than i2c_write (once max 4 bytes).

/* Close i2c bus */
void i2c_close(int bus);

/* Open i2c bus, return i2c bus fd */
int i2c_open(const char *bus_name);

/* I2C file I/O read, write */
ssize_t i2c_read(const I2CDevice *device, unsigned int iaddr, void *buf, size_t len);
ssize_t i2c_write(const I2CDevice *device, unsigned int iaddr, const void *buf, size_t len);

/* I2c ioctl read, write can set i2c flags */
ssize_t i2c_ioctl_read(const I2CDevice *device, unsigned int iaddr, void *buf, size_t len);
ssize_t i2c_ioctl_write(const I2CDevice *device, unsigned int iaddr, const void *buf, size_t len);

Data structure

C/C++

typedef struct i2c_device {
	int bus;			/* I2C Bus fd, return from i2c_open */
	unsigned short addr;		/* I2C device(slave) address */
	unsigned char tenbit;		/* I2C is 10 bit device address */
	unsigned char delay;		/* I2C internal operate delay, unit millisecond */
	unsigned short flags;		/* I2C i2c_ioctl_read/write flags */
	unsigned int page_bytes;    	/* I2C max number of bytes per page, 1K/2K 8, 4K/8K/16K 16, 32K/64K 32 etc */
	unsigned int iaddr_bytes;	/* I2C device internal(word) address bytes, such as: 24C04 1 byte, 24C64 2 bytes */
}I2CDevice;

Python

I2CDevice object
I2CDevice(bus, addr, tenbit=False, iaddr_bytes=1, page_bytes=8, delay=1, flags=0)
tenbit, delay, flags, page_bytes, iaddr_bytes are attributes can setter/getter after init

required args: bus, addr.
optional args: tenbit(defult False, 7-bit), delay(defualt 1ms), flags(defualt 0), iaddr_bytes(defualt 1 byte internal address), page_bytes(default 8 bytes per page).

C/C++ Usage

1. First call i2c_open open i2c bus.

int bus;

/* Open i2c bus /dev/i2c-0 */
if ((bus = i2c_open("/dev/i2c-0")) == -1) {

	/* Error process */
}

2. Second fill I2CDevice struct, prepare read or write.

I2CDevice device;
memset(&device, 0, sizeof(device));

/* 24C04 */
device.bus = bus;	/* Bus 0 */
device.addr = 0x50;	/* Slave address is 0x50, 7-bit */
device.iaddr_bytes = 1;	/* Device internal address is 1 byte */
device.page_bytes = 16; /* Device are capable of 16 bytes per page */

3. Call i2c_read/write or i2c_ioctl_read/write read or write i2c device.

unsigned char buffer[256];
ssize_t size = sizeof(buffer);
memset(buffer, 0, sizeof(buffer));

/* From i2c 0x0 address read 256 bytes data to buffer */
if ((i2c_read(&device, 0x0, buffer, size)) != size) {

	/* Error process */
}

4. Close i2c bus i2c_close(bus).

i2c_close(bus);

Python Usage

import ctypes
import pylibi2c

# Open i2c device @/dev/i2c-0, addr 0x50.
i2c = pylibi2c.I2CDevice('/dev/i2c-0', 0x50)

# Open i2c device @/dev/i2c-0, addr 0x50, 16bits internal address
i2c = pylibi2c.I2CDevice('/dev/i2c-0', 0x50, iaddr_bytes=2)

# Set delay
i2c.delay = 10

# Set page_bytes
i2c.page_bytes = 16

# Set flags
i2c.flags = pylibi2c.I2C_M_IGNORE_NAK

# Python2
buf = bytes(bytearray(256))

# Python3
buf = bytes(256)

# Write data to i2c, buf must be read-only type
size = i2c.write(0x0, buf)

# From i2c 0x0(internal address) read 256 bytes data, using ioctl_read.
data = i2c.ioctl_read(0x0, 256)

Notice

1. If i2c device do not have internal address, please use i2c_ioctl_read/write function for read/write, set'iaddr_bytes=0.

2. If want ignore i2c device nak signal, please use i2c_ioctl_read/write function, set I2CDevice.falgs as I2C_M_IGNORE_NAK.