/*
* wiringPiI2C.c:
* Simplified I2C access routines
* Copyright (c) 2013 Gordon Henderson
***********************************************************************
* This file is part of wiringPi:
* https://projects.drogon.net/raspberry-pi/wiringpi/
*
* wiringPi is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* wiringPi is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with wiringPi.
* If not, see .
***********************************************************************
*/
/*
* Notes:
* The Linux I2C code is actually the same (almost) as the SMBus code.
* SMBus is System Management Bus - and in essentially I2C with some
* additional functionality added, and stricter controls on the electrical
* specifications, etc. however I2C does work well with it and the
* protocols work over both.
*
* I'm directly including the SMBus functions here as some Linux distros
* lack the correct header files, and also some header files are GPLv2
* rather than the LGPL that wiringPi is released under - presumably because
* originally no-one expected I2C/SMBus to be used outside the kernel -
* however enter the Raspberry Pi with people now taking directly to I2C
* devices without going via the kernel...
*
* This may ultimately reduce the flexibility of this code, but it won't be
* hard to maintain it and keep it current, should things change.
*
* Information here gained from: kernel/Documentation/i2c/dev-interface
* as well as other online resources.
*********************************************************************************
*/
#include
#include
#include
#include
#include
#include
#include
#include
#include "wiringPi.h"
#include "wiringPiI2C.h"
// I2C definitions
#define I2C_SLAVE 0x0703
#define I2C_SMBUS 0x0720 /* SMBus-level access */
#define I2C_SMBUS_READ 1
#define I2C_SMBUS_WRITE 0
// SMBus transaction types
#define I2C_SMBUS_QUICK 0
#define I2C_SMBUS_BYTE 1
#define I2C_SMBUS_BYTE_DATA 2
#define I2C_SMBUS_WORD_DATA 3
#define I2C_SMBUS_PROC_CALL 4
#define I2C_SMBUS_BLOCK_DATA 5
#define I2C_SMBUS_I2C_BLOCK_BROKEN 6
#define I2C_SMBUS_BLOCK_PROC_CALL 7 /* SMBus 2.0 */
#define I2C_SMBUS_I2C_BLOCK_DATA 8
// SMBus messages
#define I2C_SMBUS_BLOCK_MAX 32 /* As specified in SMBus standard */
#define I2C_SMBUS_I2C_BLOCK_MAX 32 /* Not specified but we use same structure */
// Structures used in the ioctl() calls
union i2c_smbus_data
{
uint8_t byte ;
uint16_t word ;
uint8_t block [I2C_SMBUS_BLOCK_MAX + 2] ; // block [0] is used for length + one more for PEC
} ;
struct i2c_smbus_ioctl_data
{
char read_write ;
uint8_t command ;
int size ;
union i2c_smbus_data *data ;
} ;
static inline int i2c_smbus_access (int fd, char rw, uint8_t command, int size, union i2c_smbus_data *data)
{
struct i2c_smbus_ioctl_data args ;
args.read_write = rw ;
args.command = command ;
args.size = size ;
args.data = data ;
return ioctl (fd, I2C_SMBUS, &args) ;
}
/*
* wiringPiI2CRead:
* Simple device read
*********************************************************************************
*/
int wiringPiI2CRead (int fd)
{
union i2c_smbus_data data ;
if (i2c_smbus_access (fd, I2C_SMBUS_READ, 0, I2C_SMBUS_BYTE, &data))
return -1 ;
else
return data.byte & 0xFF ;
}
/*
* wiringPiI2CReadReg8: wiringPiI2CReadReg16:
* Read an 8 or 16-bit value from a regsiter on the device
*********************************************************************************
*/
int wiringPiI2CReadReg8 (int fd, int reg)
{
union i2c_smbus_data data;
if (i2c_smbus_access (fd, I2C_SMBUS_READ, reg, I2C_SMBUS_BYTE_DATA, &data))
return -1 ;
else
return data.byte & 0xFF ;
}
int wiringPiI2CReadReg16 (int fd, int reg)
{
union i2c_smbus_data data;
if (i2c_smbus_access (fd, I2C_SMBUS_READ, reg, I2C_SMBUS_WORD_DATA, &data))
return -1 ;
else
return data.word & 0xFFFF ;
}
/*
* wiringPiI2CWrite:
* Simple device write
*********************************************************************************
*/
int wiringPiI2CWrite (int fd, int data)
{
return i2c_smbus_access (fd, I2C_SMBUS_WRITE, data, I2C_SMBUS_BYTE, NULL) ;
}
/*
* wiringPiI2CWriteReg8: wiringPiI2CWriteReg16:
* Write an 8 or 16-bit value to the given register
*********************************************************************************
*/
int wiringPiI2CWriteReg8 (int fd, int reg, int value)
{
union i2c_smbus_data data ;
data.byte = value ;
return i2c_smbus_access (fd, I2C_SMBUS_WRITE, reg, I2C_SMBUS_BYTE_DATA, &data) ;
}
int wiringPiI2CWriteReg16 (int fd, int reg, int value)
{
union i2c_smbus_data data ;
data.word = value ;
return i2c_smbus_access (fd, I2C_SMBUS_WRITE, reg, I2C_SMBUS_WORD_DATA, &data) ;
}
/*
* wiringPiI2CSetupInterface:
* Undocumented access to set the interface explicitly - might be used
* for the Pi's 2nd I2C interface...
*********************************************************************************
*/
int wiringPiI2CSetupInterface (const char *device, int devId)
{
int fd ;
if ((fd = open (device, O_RDWR)) < 0)
return wiringPiFailure (WPI_ALMOST, "Unable to open I2C device: %s\n", strerror (errno)) ;
if (ioctl (fd, I2C_SLAVE, devId) < 0)
return wiringPiFailure (WPI_ALMOST, "Unable to select I2C device: %s\n", strerror (errno)) ;
return fd ;
}
/*
* wiringPiI2CSetup:
* Open the I2C device, and regsiter the target device
*********************************************************************************
*/
int wiringPiI2CSetup (const int devId)
{
int rev ;
const char *device ;
rev = piGpioLayout () ;
if (rev == 1)
device = "/dev/i2c-0" ;
else
device = "/dev/i2c-1" ;
return wiringPiI2CSetupInterface (device, devId) ;
}