14. I2C

The I2C object is a built-in object that provides I2C communication functions.

Functional overview:

• Provides I2C master mode function.

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Abstracts

Methods()/Properties	Summary	Version	Note
new I2C()	Creates an I2C instance.	01.00.00+

{I2C} Instance

Methods()/Properties	Summary	Version	Note
.open()	Starts the communication.	01.00.00+
.close()	Ends the communication.	01.00.00+
.write()	Writes the data.	01.00.00+
.read()	Reads the data.	01.00.00+
.writeRead()	Reads the data after writing the data.	01.00.00+

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Details

new I2C(nodeNo)

Creates an I2C instance.

Name	Type	M/O	Summary	Note
nodeNo	number	mandatory	Specifies the node number of the I2C interface to be used. Please refer to Pinout.
return	{I2C}	-	{I2C} : Generated {I2C}

.open(baudrate)

Starts the communication.

Name	Type	M/O	Summary	Note
baudrate	number	mandatory	Communication speed Specify the communication baudrate [bps]. Range: 100000, 400000
return	boolean	-	true: Success false: Failure

.close()

Ends the communication.

Name	Type	M/O	Summary	Note
return	boolean	-	true: Success false: Failure

.write(slaveAddr,buff)

Writes the data.

Name	Type	M/O	Summary	Note
slaveAddr	number	mandatory	Slave address of the I2C device Range: 0 - 127 (7 bit)
buff	ArrayBuffer	mandatory	Write data ArrayBuffer size will be written.	The size that can be written at a time is 255 bytes.
return	boolean	-	true: Success false: Failure

When the data length is 1 byte, use Uint8Array as follows.

var buff = new ArrayBuffer(1);
var arr = new Uint8Array(buff);
arr[0] = your_data;
var ret = i2c.write(slave_address, buff);

.read(slaveAddr,len)

Reads the data.

Name	Type	M/O	Summary	Note
slaveAddr	number	mandatory	Slave address of the I2C device Range: 0 - 127 (7 bit)
len	number	mandatory	Specify the read data length.	The maximum size that can be read at a time is 255 bytes.
return	Arraybuffer	-	Read data If read function fails, the returned size will be 0.

.writeRead(slaveAddr,buff,len)

Reads the data after writing the data.

Name	Type	M/O	Summary	Note
slaveAddr	number	mandatory	Slave address of the I2C device Range: 0 - 127 (7 bit)
buff	ArrayBuffer	mandatory	Write data ArrayBuffer size will be written.	The size that can be written at a time is 255 bytes.
len	number	mandatory	Specify the read data length.	The maximum size that can be read at a time is 255 bytes.
return	Arraybuffer	-	Read data If the reading fails, the returned size will be 0.

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Object Usage Examples

Sample 1

This sample is an I2C device with a slave address of 0x3A, which writes 0x03 to register 0x05, and then reads 1 byte from register 0x06.

var NODE_NO = 0;
var BAUDRATE = 400000;
var SLAVE_ADDR = 0x3A; //slave address

//I2C write function
var write = function(i2c, reg, data) {
    var buf = new ArrayBuffer(2);
    var arr = new Uint8Array(buf);
    arr[0] = reg;
    arr[1] = data;
    var ret = i2c.write(SLAVE_ADDR, buf);
    if (!ret) print('I2C write error');
    return ret;
};

//I2C read function
var read = function(i2c, reg) {
    var buf = new ArrayBuffer(1);
    var arr = new Uint8Array(buf);
    arr[0] = reg;
    if(!i2c.write(SLAVE_ADDR, buf)) {
        print('I2C read error');
        return 0;
    }
    var retBuf = i2c.read(SLAVE_ADDR, 1);
    if (!retBuf.byteLength) print('I2C read error2');
    var ret = new Uint8Array(retBuf);
    return ret[0];
};

var i2c = new I2C(NODE_NO);
i2c.open(BAUDRATE);

write(i2c, 0x05, 0x03);
read(i2c, 0x06);

i2c.close();

Sample 2

This sample is an I2C device with a slave address of 0x3A, which writes 0x03 to register 0x05, and then reads 1 byte.

var NODE_NO = 0;
var BAUDRATE = 400000;
var SLAVE_ADDR = 0x3A; //slave address

//I2C writeRead function
var writeRead = function(i2c, reg, data) {
    var buf = new ArrayBuffer(2);
    var arr = new Uint8Array(buf);
    arr[0] = reg;
    arr[1] = data;
    var retBuf = i2c.writeRead(SLAVE_ADDR, buf, 1);
    if (!retBuf.byteLength) print('I2C write read error');
    var ret = new Uint8Array(retBuf);
    return ret[0];
};

var i2c = new I2C(NODE_NO);
i2c.open(BAUDRATE);

writeRead(i2c, 0x05, 0x03);

i2c.close();

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Updated: 2020-09-18