nodemcu-firmware/docs/en/modules/i2c.md

I²C Module

Since	Origin / Contributor	Maintainer	Source
2014-12-22	Zeroday	Zeroday	i2c.c

i2c.address()

Setup I²C address and read/write mode for the next transfer.

Syntax

i2c.address(id, device_addr, direction)

Parameters

• id always 0
• device_addr 7-bit device address, remember that in I²C device_addr represents the upper 7 bits followed by a single direction bit
• direction i2c.TRANSMITTER for writing mode , i2c. RECEIVER for reading mode

Returns

true if ack received, false if no ack received.

See also

i2c.read()

i2c.read()

Read data for variable number of bytes.

Syntax

i2c.read(id, len)

Parameters

• id always 0
• len number of data bytes

Returns

string of received data

Example

id  = 0
sda = 1
scl = 2

-- initialize i2c, set pin1 as sda, set pin2 as scl
i2c.setup(id, sda, scl, i2c.SLOW)

-- user defined function: read from reg_addr content of dev_addr
function read_reg(dev_addr, reg_addr)
    i2c.start(id)
    i2c.address(id, dev_addr, i2c.TRANSMITTER)
    i2c.write(id, reg_addr)
    i2c.stop(id)
    i2c.start(id)
    i2c.address(id, dev_addr, i2c.RECEIVER)
    c = i2c.read(id, 1)
    i2c.stop(id)
    return c
end

-- get content of register 0xAA of device 0x77
reg = read_reg(0x77, 0xAA)
print(string.byte(reg))

####See also i2c.write()

i2c.setup()

Initialize the I²C module.

Syntax

i2c.setup(id, pinSDA, pinSCL, speed)

####Parameters

• id always 0
• pinSDA 1~12, IO index
• pinSCL 1~12, IO index
• speed only i2c.SLOW supported

Returns

speed the selected speed

####See also i2c.read()

i2c.start()

Send an I²C start condition.

Syntax

i2c.start(id)

Parameters

id always 0

Returns

nil

####See also i2c.read()

i2c.stop()

Send an I²C stop condition.

Syntax

i2c.stop(id)

####Parameters id always 0

Returns

nil

####See also i2c.read()

i2c.write()

Write data to I²C bus. Data items can be multiple numbers, strings or lua tables.

####Syntax i2c.write(id, data1[, data2[, ..., datan]])

####Parameters

• id always 0
• data data can be numbers, string or lua table.

Returns

number number of bytes written

Example

i2c.write(0, "hello", "world")

See also

i2c.read()