[beagleboard] BeagleBone intefacing PCF8574...

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1

Seems there is an experimental kernel driver for this chip under misc
sensors in the kernel tree. might look there and use that.

Eric

2

I believe that 8574-specific driver is deprecated, and the gpio-based replacement is bit-level only. Anyway, it isn't necessary. You can use the basic i2c drivers. I use something like this to communicate with 8574 devices:

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/i2c.h>
#include <linux/i2c-dev.h>
#include <glib.h>

#define I2C_BUS "/dev/i2c-3"

gboolean write_error_flagged;
gboolean read_error_flagged;

void I2C_Write(gulong address, guchar value)
{
         struct i2c_smbus_ioctl_data argswrite;

         argswrite.read_write = I2C_SMBUS_WRITE;
         argswrite.size = I2C_SMBUS_BYTE;
         argswrite.data = NULL;
         argswrite.command = value;

         int device = open(I2C_BUS, O_RDWR);

         if ((device == -1) && !write_error_flagged) {
                 write_error_flagged = TRUE;
                 g_print_debug("ERROR: could not open I2C bus %s for writing\n", I2C_BUS);
                 return;
         }

         ioctl(device, I2C_SLAVE, address);
         ioctl(device, I2C_SMBUS, &argswrite);

         close(device);
}

guchar I2C_Read(gulong address)
{

         union i2c_smbus_data data;
         struct i2c_smbus_ioctl_data argsread;

         argsread.read_write = I2C_SMBUS_READ;
         argsread.size = I2C_SMBUS_BYTE;
         argsread.data = &data;
         argsread.command = 0;

         int device = open(I2C_BUS, O_RDWR);

         if ((device == -1) && !read_error_flagged) {
                 read_error_flagged = TRUE;
                 g_print_debug("ERROR: could not open I2C bus %s for reading\n", I2C_BUS);
                 return 0;
         }

         ioctl(device, I2C_SLAVE, address);
         ioctl(device, I2C_SMBUS, &argsread);

         close(device);

         return data.byte;
}