MaixCAM MaixPy Using I2C

2025-08-08

Update history

Date	Version	Author	Update content
2025-08-08	1.1.0	Neucrack	Refactored the documentation to be more understandable for beginners

Prerequisites

Please learn how to use the pinmap module to set pin functions first.

To enable an pin for I2C functionality, first use pinmap to set the function of the corresponding pin to I2C.

I2C Introduction

I2C uses only two pins, SCL and SDA, to achieve bus communication. This allows one master to connect to multiple slaves, enabling convenient one-to-many communication.
It is commonly used for:

Reading sensor data, such as temperature and humidity, IMU, and touchscreens.
Controlling devices, such as setting camera parameters.
Communication between two devices.

There are many good tutorials on the basics of I2C online. This article will not go into detail; please search and learn on your own.

Choosing the Right I2C to Use

First, we need to know which pins and I2C interfaces the device has, as shown in the figure:

Device Model	Pinout Diagram	Pin Multiplexing Description
MaixCAM		The silkscreen on the board, e.g., `A15`, is the pin name, and `I2C5_SCL` is the function name
MaixCAM-Pro		The first name, e.g., `A15`, is the pin name, and `I2C5_SCL` is the corresponding function name
MaixCAM2		The first name, e.g., `IO0_A1`, is the pin name, and `I2C6_SCL` is the corresponding function name

It's important to note that pins might have other default uses. It's best to avoid these pins. Please refer to the pinmap documentation for details.

For example:

For MaixCAM / MaixCAM-Pro, the I2C1 and I2C3 pins overlap with the WiFi module (SDIO1), so their use is not recommended. There is also an I2C5, which is a software-simulated driver at the low level. It is recommended to use it as the underlying driver has been configured, and it works the same as a hardware I2C.
The I2C6 / I2C7 pins on MaixCAM2 are idle and can be used once pinmap is configured.

Using I2C in MaixPy

First, use pinmap to set the pin function to I2C, then initialize the I2C object:

from maix import i2c, pinmap, sys, err


# get pin and i2c number according to device id
device_id = sys.device_id()
if device_id == "maixcam2":
    scl_pin_name = "IO0_A1"
    scl_i2c_name = "I2C6_SCL"
    sda_pin_name = "IO0_A0"
    sda_i2c_name = "I2C6_SDA"
    i2c_id = 6
else:
    scl_pin_name = "A15"
    scl_i2c_name = "I2C5_SCL"
    sda_pin_name = "A27"
    sda_i2c_name = "I2C5_SDA"
    i2c_id = 5

# set pinmap
err.check_raise(pinmap.set_pin_function(scl_pin_name, scl_i2c_name), "set pin failed")
err.check_raise(pinmap.set_pin_function(sda_pin_name, sda_i2c_name), "set pin failed")

bus = i2c.I2C(i2c_id, i2c.Mode.MASTER)
slaves = bus.scan()
print("find slaves:")
for s in slaves:
    print(f"{s}[0x{s:02x}]")

More Examples

See MaixPy examples.

API Documentation

For more API information, see i2c API documentation.

Using Other Libraries

Additionally, since it is a standard Linux driver, besides using the APIs provided by MaixPy, you can also use general Linux libraries like smbus / smbus2.

Steps to use:

Run pip install smbus in the development board's terminal to install the library.
Use pinmap to map the pin functions.
Call smbus APIs to read from and write to i2c.

from maix import i2c, pinmap, sys, err
import smbus

# get pin and i2c number according to device id
device_id = sys.device_id()
if device_id == "maixcam2":
    scl_pin_name = "IO0_A1"
    scl_i2c_name = "I2C6_SCL"
    sda_pin_name = "IO0_A0"
    sda_i2c_name = "I2C6_SDA"
    i2c_id = 6
else:
    scl_pin_name = "A15"
    scl_i2c_name = "I2C5_SCL"
    sda_pin_name = "A27"
    sda_i2c_name = "I2C5_SDA"
    i2c_id = 5

# set pinmap
err.check_raise(pinmap.set_pin_function(scl_pin_name, scl_i2c_name), "set pin failed")
err.check_raise(pinmap.set_pin_function(sda_pin_name, sda_i2c_name), "set pin failed")


bus = smbus.SMBus(i2c_id)

UART

PWM