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Today, I will talk to you about the example analysis of Linux I2C App development, which may not be well understood by many people. In order to let everyone know more, Xiaobian summarized the following contents for everyone. I hope you can gain something according to this article.

1, header file

/linux/i2c-dev.h

2 , Open the file, please see the sample code

int file; int adapter_nr = 1; /* I2C adapter number */ char filename[20]; snprintf(filename, 19, "/dev/i2c-%d", adapter_nr); file = open(filename, O_RDWR); if (file < 0) { /* Failed to open */ exit(1);}

3 , Specify I2C slave address

int addr = 0x40; /* I2C slave address */ if (ioctl(file, I2C_SLAVE, addr) < 0) { /* Failed to open */ exit(1);}

4, Access devices using SMBUS API

5, SMBUS detailed interface timing description

Tag Length Description S1 bitI2C Start P1 bitI2C Stop Rd/Wr1 bit Read flag bit in control word, read operation is 1, write operation is 0A, NA1 bit Reply flag Addr7 bits7 bits I2C address Data8 bits Byte Data Comm8 bits Command byte, can be understood as I2C device register address [..] N charI2C device returns data

6. Description of relevant interfaces and corresponding timing

【1】__s32 i2c_smbus_write_quick(int file, __u8 value);

Send a write control word that can be used to test for the presence of an I2C device.

S Addr Rd [A] [Data] NA P

【2】__s32 i2c_smbus_read_byte(int file);

Send a read control word and read a byte from the I2C device.

S Addr Rd [A] [Data] NA P

【3】__s32 i2c_smbus_write_byte(int file, __u8 value);

Send a write control word and write a byte to the I2C device.

S Addr Wr [A] Data [A] P

【4】__s32 i2c_smbus_read_byte_data(int file, __u8 command);

Send a write control word + control instruction (register address) to the I2C device, and then send a read control word. At this time, the I2C moves from the read-write pointer inside the device to the specified position, returns a byte, and finally returns a no response NA.

S Addr Wr [A] Comm [A] S Addr Rd [A] [Data] NA P

【5】__s32 i2c_smbus_write_byte_data(int file, __u8 command, __u8 value);

A write control word + control command (register address) is sent to the I2C device, followed by the command contents (register contents, single byte).

S Addr Wr [A] Comm [A] Data [A] P

【6】__s32 i2c_smbus_read_i2c_block_data(int file, __u8 command, __u8 *values);

Send a write control word + control instruction (register address) to the I2C device, and then send a read control word. At this time, the I2C moves from the read/write pointer inside the device to the specified position and returns multiple bytes continuously. After the I2C host reads a certain number of bytes, it sends no response NA.

S Addr Wr [A] Comm [A] S Addr Rd [A] [Data] A [Data] A ... A [Data] NA P

【7】__s32 i2c_smbus_write_i2c_block_data(int file, __u8 command, __u8 length, __u8 *values);

Send a write control word + control command (register address) to the I2C device followed by send command contents (register contents, multibyte)

S Addr Wr [A] Comm [A] Data [A] Data [A] ... [A] Data [A] P

[Note 1]

These functions fail if they return-1. In some write functions, 0 is returned for success, and in read functions, the number of bytes read (except i2c_smbus_read_block_data) is returned. Read block operations should not exceed 32 bytes.

After reading the above, do you have any further understanding of the sample analysis of Linux I2C App development? If you still want to know more knowledge or related content, please pay attention to the industry information channel, thank you for your support.

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