M5Stack_Linux_Libs/doc/example_doc/linux_i2c.md

## I2C
I2C (Inter-Integrated Circuit) bus, this is a common serial communication protocol used to connect multiple microcontrollers, sensors, chips, and other external devices.

Here are important concepts about I2C that beginners need to understand:

1. **Serial Communication:** I2C is a serial communication protocol that allows multiple devices to communicate on the same line, greatly reducing the number of connecting lines.

2. **Two-Wire System:** I2C uses two lines for communication: SCL (Serial Clock Line) and SDA (Serial Data Line). SCL is used to transmit clock signals, while SDA is used to transmit data.

3. **Master-Slave Structure:** I2C communication typically involves two types of devices: master devices and slave devices. The master device generates clock signals and controls communication, while the slave devices respond to instructions from the master device.

4. **Address Allocation:** Each slave device has a unique 7-bit address on the bus, and the master device uses these addresses to select specific slave devices for communication.

5. **Frame Format:** I2C communication consists of a series of data frames. Each frame typically includes a start bit, an address byte, data bytes, and a stop bit.

6. **Clock Synchronization:** The I2C protocol uses clock signals generated by the master device to synchronize communication, ensuring data is transmitted at the correct time.

7. **Speed:** The I2C communication speed can be set as needed. Standard mode (100 Kbps) and fast mode (400 Kbps) are common speeds.

8. **Applications:** I2C is widely used in embedded systems, sensors, storage devices, displays, electronic chips, and other fields.

examples:

```c
#include <stdio.h>
#include <linux_i2c/linuxi2c.h>
#include <assert.h>
// Define a bus object
LINUXI2CDevice i2cdev;
int main(int argc,char *argv[])
{
    char i2c_bus[20] = "/dev/i2c-1";
    int ret;
    // init bus object
    linuxi2c_init_device(&i2cdev);
    // open bus
    i2cdev.bus = linuxi2c_open(i2c_bus);
    if(i2cdev.bus <= 0)
    {
        printf("i2c bus: %s open fail!\b", i2c_bus);
        abort();
    }
    char data = 0x01;
    // write data
    ret = linuxi2c_write(&i2cdev, 0x3c, &data, 1);
    if(ret < 0)
    {
        goto end;
    }
    data = 0;
    // read data
    ret = linuxi2c_read(&i2cdev, 0x3c, &data, 1);
    if(ret < 0)
    {
        goto end;
    }
    printf("get i2c bus:%s addr:0x3c val:%x\n", i2c_bus, data);
    end:
        // Release the i2c bus
        linuxi2c_close(i2cdev.bus);

    return 0;
}
```

When compiling the above program, you can compile and run it in the examples/linux_i2c directory of [M5Stack_Linux_Libs]().  
Enter the Linux device:
``` bash
# Clone repository
git clone https://github.com/M5STACK/M5Stack_Linux_Libs.git

# Enter directory
cd M5Stack_Linux_Libs/examples/linux_i2c

# Compile
scons 

```