Using I2C in C¶

I2C API

Initialization¶

The first step in using I2C is to bring up the connection to the I2C bus. The k_i2c_init() function will initialize a connection with the specified I2C bus and return a file descriptor which should be passed to the other functions.

KI2CStatus status;

// Initialize our file descriptor storage variable
int bus = 0;
// Open a connection to I2C bus 1
status = k_i2c_init("/dev/i2c-1", &bus);
if (status != I2C_OK)
{
    fprintf(stderr, "Failed to initialize I2C bus connection: %d\n", status);
    return -1;
}

Writing¶

The k_i2c_write() function should be used to write to an I2C device. The function takes four arguments:

The file descriptor of the I2C bus to use for communication
The I2C address of the slave device
A pointer to the data to be written
The number of bytes to be written

The function returns a KI2CStatus value. I2C_OK indicates that the function completed successfully.

KI2CStatus status;
int bus = 0;
k_i2c_init("/dev/i2c-1", &bus);

char cmd = 0x40;
int slave_addr = 0x80;

status = k_i2c_write(bus, slave_addr, &cmd, 1);
if (status != I2C_OK)
{
    fprintf(stderr, "Failed to write to I2C device: %d\n", status);
    return -1;
}

Reading¶

The k_i2c_read() function should be used to read data from an I2C device. The function takes four arguments:

The file descriptor of the I2C bus to use for communication
The I2C address of the slave device
A pointer to the read buffer
The number of bytes to be read

The function returns a KI2CStatus value. I2C_OK indicates that the function completed successfully.

KI2CStatus status;
int bus = 0;
k_i2c_init("/dev/i2c-1", &bus);

char buffer[100];
int slave_addr = 0x80;

status = k_i2c_read(bus, slave_addr, buffer, 10);
if (status != I2C_OK)
{
    fprintf(stderr, "Failed to read from I2C device: %d\n", status);
    return -1;
}

Termination¶

Once all I2C work has been completed, the k_i2c_terminate() function should be used to close the connection with the I2C bus and perform system cleanup.

int bus = 0;
k_i2c_init("/dev/i2c-1", &bus);

k_i2c_terminate(&bus);