machine.I2C

I2C bus protocol, simply using two lines (SCL, SDA) can control multiple slaves (master mode).

• Supports master mode and slave mode
• 7-bit / 10-bit addressing mode
• Standard mode <= 100Kb / s
• Fast mode <= 400Kb / s
• Super fast mode <= 1000Kb / s
• High-speed mode 3.4Mb / s

1. Constructor

class machine.I2C (id, mode = I2C.MODE_MASTER, scl = None, sda = None, freq = 400000, timeout = 1000, addr = 0, addr_size = 7, on_recieve = None, on_transmit = None, on_event = None)

Create a new I2C object with the specified parameters

1.1. Parameters

• id: I2C ID, [0 ~ 2] \ (I2C.I2C0 ~ I2C.I2C2 )
• mode: mode, master (I2C.MODE_MASTER) and slave (I2C.MODE_SLAVE) mode
• scl: SCL pin, just pass the pin number directly, value range: [0,47]. Instead of setting it, use [fm] (../ builtin_py / fm.md) to manage the pin mapping uniformly.
• sda: SDA pin, just pass the pin number directly, value range: [0,47]. Instead of setting it, use [fm] (../ builtin_py / fm.md) to manage the pin mapping uniformly.
• freq: I2C communication frequency, support standard 100Kb / s, fast 400Kb / s, and higher speed (hardware supports super fast mode 1000Kb / s, and high-speed mode 3.4Mb / s)
• timeout: timeout time, currently this parameter is reserved, setting is invalid
• addr: slave address, if it is in master mode, it is not necessary to set, slave mode represents slave (local) address
• addr_size: address length, support 7-bit addressing and 10-bit addressing, value7 or 10
• on_recieve: Receive callback function in slave mode
• on_transmit: Send callback function in slave mode
• on_event: Slave mode event function (start event and end event)

2. Method

2.1. init

Constructor-like

I2C.init (id, mode = Timer.MODE_MASTER, scl, sda, freq = 400000, timeout = 1000, addr = 0, addr_size = 7, on_recieve = None, on_transmit = None, on_event = None)

parameters

Same as constructor

return value

no

2.2. scan

Scanning slaves on the I2C bus

I2C.scan ()

parameters

no

return value

list object containing all scanned slave addresses

2.3. readfrom

Read data from the bus

I2C.readfrom (addr, len, stop = True)

parameters

• addr: slave address
• len: data length
• stop: Whether to generate a stop signal. Reserved. Currently, only the default value True can be used.

return value

Read data, type bytes

2.4. readfrom_into

Read the data and put it into the specified variable

I2C.readfrom_into (addr, buf, stop = True)

parameters

• addr: slave address
• buf:bytearray type, which defines the length, and the read data is stored here
• stop: Whether to generate a stop signal. Reserved. Currently, only the default value True can be used.

return value

no

2.5. writeto

Send data to the slave

I2C.writeto (addr, buf, stop = True)

parameters

• addr: slave address
• buf: data to be sent
• stop: Whether to generate a stop signal. Reserved. Currently, only the default value True can be used.

return value

Number of bytes successfully sent

2.6. readfrom_mem

Read slave register

I2C.readfrom_mem (addr, memaddr, nbytes, mem_size = 8)

parameters

• addr: slave address
• memaddr: slave register address
• nbytes: the length to read
• mem_size: register width, default is 8 bits

return value

Returns read data of type bytes

2.7. readfrom_mem_into

Read the slave register value into the specified variable

I2C.readfrom_mem_into (addr, memaddr, buf, mem_size = 8)

parameters

• addr: slave address
• memaddr: slave register address
• buf:bytearray type, which defines the length, and the read data is stored here
• mem_size: register width, default is 8 bits

return value

no

2.8. writeto_mem

Write data to slave register

I2C.writeto_mem (addr, memaddr, buf, mem_size = 8)

parameters

• addr: slave address
• memaddr: slave register address
• buf: data to be written
• mem_size: register width, default is 8 bits

return value

no

2.9. deinit / \ del \

Log off the I2C hardware, release the occupied resources, and shut down the I2C clock

I2C.deinit ()

parameters

no

return value

no

Examples

i2c.deinit ()

or

del i2c

3. Constants

• I2C0: I2C 0
• I2C1: I2C 1
• I2C2: I2C 2
• MODE_MASTER: as master mode
• MODE_SLAVE: as slave mode
• I2C_EV_START: event type, start signal
• I2C_EV_RESTART: event type, restart signal
• I2C_EV_STOP: event type, end signal

4. Examples

4.1. Routine 1: Scanning for Slave Devices

from machine import I2C

i2c = I2C (I2C.I2C0, freq = 100000, scl = 28, sda = 29)
devices = i2c.scan ()
print (devices)

4.2. Example 2: Read and write

import time
from machine import I2C

i2c = I2C (I2C.I2C0, freq = 100000, scl = 28, sda = 29)
i2c.writeto (0x24, b'123 ')
i2c.readfrom (0x24,5)

4.3. Example 3: Slave mode

from machine import I2C

count = 0

def on_receive (data):
    print ("on_receive:", data)

def on_transmit ():
    count = count + 1
    print ("on_transmit, send:", count)
    return count

def on_event (event):
    print ("on_event:", event)

i2c = I2C (I2C.I2C0, mode = I2C.MODE_SLAVE, scl = 28, sda = 29, addr = 0x24, addr_size = 7, on_receive = on_receive, on_transmit = on_transmit, on_event = on_event)

4.4. Example 4: OLED (ssd1306 128x64)

import time
from machine import I2C

SSD1306_CMD = 0
SSD1306_DATA = 1
SSD1306_ADDR = 0x3c

def oled_init (i2c):
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0xAE, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0x20, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0x10, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0xb0, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0xc8, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0x00, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0x10, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0x40, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0x81, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0xff, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0xa1, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0xa6, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0xa8, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0x3F, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0xa4, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0xd3, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0x00, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0xd5, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0xf0, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0xd9, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0x22, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0xda, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0x12, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0xdb, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0x20, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0x8d, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0x14, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0xaf, mem_size = 8)



def oled_on (i2c):
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0X8D, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0X14, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0XAF, mem_size = 8)

def oled_off (i2c):
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0X8D, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0X10, mem_size = 8)
    i2c.writeto_mem (SSD1306_ADDR, 0x00, 0XAE, mem_size = 8)

def oled_fill (i2c, data):
    for i in range (0,8):
        i2c.writeto_mem (SSD1306_ADDR, 0x00, 0xb0 + i, mem_size = 8)
        i2c.writeto_mem (SSD1306_ADDR, 0x00, 0x10, mem_size = 8)
        i2c.writeto_mem (SSD1306_ADDR, 0x00, 0x01, mem_size = 8)
        for j in range (0,128):
            i2c.writeto_mem (SSD1306_ADDR, 0x40, data, mem_size = 8)

i2c = I2C (I2C.I2C0, mode = I2C.MODE_MASTER, freq = 400000, scl = 28, sda = 29, addr_size = 7)

time.sleep (1)
oled_init (i2c)
oled_fill (i2c, 0xff)