Advantech RSB-4210 Evaluation Kit User Manual download pdf (Page 65)

57 RSB-4210 User Manual

Chapter 3 Software Functionality

3.10.3 GPIO Mapping Table

3.11 Interface Device Reference Documentation

3.11.1 I2C

Usually, i2c devices are controlled by a kernel driver. But it is also possible to access

all devices on an adapter from userspace, through the /dev interface. You need to

load module i2c-dev for this. Each registered i2c adapter gets a number, counting

from 0. You can examine /sys/class/i2c-dev/ to see what number corresponds to

which adapter. Alternatively, you can run "i2cdetect -l" to obtain a formated list of all

i2c adapters present on your system at a given time. i2cdetect is part of the i2c-tools

package.

I2C device files are character device files with major device number 89 and a minor

device number corresponding to the number assigned as explained above. They

should be called "i2c-%d" (i2c-0, i2c-1, ..., i2c-10, ...). All 256 minor device numbers

are reserved for i2c.

3.11.2 C example

To access an i2c adapter from a C program. The first thing to do is "#include <linux/

i2c-dev.h>". Please note that there are two files named "i2c-dev.h" out there, one is

distributed with the Linux kernel and is meant to be included from kernel driver code,

the other one is distributed with i2c-tools and is meant to be included from user-

space programs. You obviously want the second one here.

Now, you have to decide which adapter you want to access. You should inspect /sys/

class/i2c-dev/ or run "i2cdetect -l" to decide this. Adapter numbers are assigned

ROM-1210 RSB-4210

Logical Number Physical Number Logical Number Physical Number

11491176

21482148

31473147

433433

51755224

61766225

72267226

82278227

92289228

10 229 10 229

11 230 11 230

12 231 12 231

13 232 13 232

14 233 14 233

15 234 15 234

16 235 16 235

17 236 17 236

18 237 18 237

19 238 19 238

20 239 20 239

1 2 ... 60 61 62 63 64 65 66 67 68 69 70 ... 103 104

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Advantech RSB-4210 Evaluation Kit User Manual Page 65

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