beaglebone_i2c.c

// http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=Documentation/i2c/dev-interface
// read and write code, without stops, from
// http://bunniestudios.com/blog/images/infocast_i2c.c
#include <stdio.h>
#include <errno.h>
#include <linux/i2c-dev.h>
#include <linux/i2c.h>
#include <fcntl.h>
#include "include/beaglebone_i2c.h"

// chain specified should match the /dev/i2c-%d entry.
// i2c-2 is hidden, so don't incrlude it in the list.
#define NUM_I2C_CHAINS 4
#define VALID_I2C_CHAINS {-1, 1, -1, 3}

typedef struct I2C_Chain {
    int file;
    unsigned char valid;
    pthread_mutex_t lock;
} I2C_Chain;

struct I2C_Chain i2cChains[NUM_I2C_CHAINS];

int I2C_Chain_init( I2C_Chain *i2cChain ){
    int retval = 0;
    pthread_mutex_init(&i2cChain->lock, NULL);
    i2cChain->valid = 0;
    i2cChain->file = -1;
    return retval;
}

#define ERROR_I2C -1
#define ERROR_I2C_HW -2

// i2c-dev.h
// 00040 #define I2C_M_TEN 0x10  /* we have a ten bit chip address */
// 00041 #define I2C_M_RD  0x01
// 00042 #define I2C_M_NOSTART 0x4000
// 00043 #define I2C_M_REV_DIR_ADDR  0x2000
// 00044 #define I2C_M_IGNORE_NAK  0x1000
// 00045 #define I2C_M_NO_RD_ACK   0x0800

int checkChain(unsigned char chain){
    // returns true if the chain is invalid
    if(chain < NUM_I2C_CHAINS){
        if( i2cChains[chain].valid ){
            return 0;
        }
    }
    fprintf(stderr, "I2C chain specified is invalid: %d\n", chain);
    return -ECHRNG;
}

int i2cChain_writeMessages(unsigned char chain, struct i2c_rdwr_ioctl_data *msgset){
    // returns 0 on success.
    int retval = 0;
    if(retval = checkChain(chain)){
        return retval;
    }
    retval = ioctl(i2cChains[chain].file, I2C_RDWR, msgset);
    return retval;
}

int i2c_write(const unsigned char chain, const unsigned int address, unsigned char *data, const unsigned int numBytes){
    // assumes address is not 10bit. if we need 10bit in the future, need to check if 10bit has been set, and enable the bit in the flags below.
    // Note: For register writing, the first data bit will usually contain the address of the device register to write.
    struct i2c_rdwr_ioctl_data i2cCommand;
    struct i2c_msg msgs[1];

    // set up write operation
    msgs[0].addr = address;
    msgs[0].flags = 0;  // no flags
    msgs[0].len = numBytes*sizeof(unsigned char);
    msgs[0].buf = data;

    i2cCommand.msgs = msgs;
    i2cCommand.nmsgs = 1;

    return i2cChain_writeMessages(chain, &i2cCommand);
}

int i2c_wtf(){
    int addr = 0x20;
    int chain = 3;
    int retval = 0;
        if( (retval = ioctl(i2cChains[chain].file, I2C_SLAVE, addr)) < 0 ){
        printf("Couldn't set ioctl i2c_slave addr: %d\n", retval);
        return -1;
    }
    printf("Errno: %d\n", errno);
    int reg = 0x05;
    unsigned char data;
    if( (retval = read(i2cChains[chain].file, &data, 1)) != 1){
        printf("Couldn't read the byte from file %d: retval = %d\n", i2cChains[chain].file, retval);
        printf("Errno: %d\n", errno);
        return retval;
    }else{
        printf("Read: %d\n", data);
    }

    return retval;
}

int i2c_read(const unsigned char chain, const unsigned int address, unsigned char reg, unsigned char *data, const unsigned char numBytes){
    // assumes address is not 10bit. if we need 10bit in the future, need to check if 10bit has been set, and enable the bit in the flags below.
    struct i2c_rdwr_ioctl_data i2cCommand;
    struct i2c_msg msgs[2];
    // write the i2c address
    msgs[0].addr = address;
    msgs[0].flags = 0;
    msgs[0].len = sizeof(reg);
    msgs[0].buf = &reg;

    // read the contents
    msgs[1].addr = address;
    msgs[1].flags = I2C_M_RD;
    msgs[1].len = numBytes;
    msgs[1].buf = data;

    i2cCommand.msgs = msgs;
    i2cCommand.nmsgs = 2;

    return i2cChain_writeMessages(chain, &i2cCommand);
}

// int i2c_TenBitAddr(unsigned int *chain, long *select{
    // // enable 10 bit addressing
    // if( ioctl(i2cChains_files[*chain], I2C_TENBIT, long select) < 0 ){
        // fprintf( stderr, "Failed to set address mode to 10 bits for i2c chain %d.\n", *chain );
        // return I2C_ERROR;
    // }
    // return 0;
// }

int i2c_initialize( void ){
    printf("Initializing I2C...\n");
    char filename[256] = {0};
    int valid_chains[] = VALID_I2C_CHAINS;
    int i, i2;

    for(i=0; i < NUM_I2C_CHAINS; i++){
        I2C_Chain_init( &i2cChains[i] );
        //printf("  i2c chain %d....", i);
        if( valid_chains[i] >= 0 ){
            sprintf(filename,"/dev/i2c-%d", valid_chains[i]);
            printf("  %s", filename);
            if( (i2cChains[i].file = open(filename, O_RDWR)) <= 0){
                fprintf(stderr, ", failed, retval = %d\n", i, i2cChains[i].file);
                for(i2 = i-1; i2 < NUM_I2C_CHAINS; i2++){
                    close(i2cChains[i2].file);
                }
                return -1;
            }else{
                i2cChains[i].valid = 1;
                printf("\n");
            }
        }else{
            // -1 means ignore the entry.
        }
    }
    return 0;
}

int i2c_cleanup( void ){
    printf("Cleaning up I2C...");
    int i;
    for(i=0; i < NUM_I2C_CHAINS; i++){
        if( i2cChains[i].valid ){
            close(i2cChains[i].file);   // don't care if it errors.
        }
    }
    printf("done.\n");
}