enableI2C

Enable I2C interface

Syntax

enableI2C(mypi)

enableI2C(mypi,i2cBusSpeed)

Description

enableI2C(mypi) enables the I2C bus at the default bus speed, 100000, and makes the GPIO pins available for use as I2C pins. By default, the I2C bus is enabled. This method works only after you use disableI2C.

For example, on a Raspberry Pi™ Model B Rev 2 board, enabling the I2C bus frees the I2C1_SDA (GPIO 2) and I2C1_SCL (GPIO 3) pins.

enableI2C(mypi,i2cBusSpeed) enables the I2C bus and overrides the current bus speed.

Examples

Connect and Exchange Data with I2C Devices

You can connect and exchange data with a pair of I2C devices.

Create a connection from the MATLAB^® software to the Raspberry Pi board.

mypi = raspi

mypi = 

  Raspi with Properties:

           DeviceAddress: 'raspberrypi-hysdu8X38o'
                    Port: 18725
               BoardName: 'Raspberry Pi Model B Rev 2'
           AvailableLEDs: {'led0'}
    AvailableDigitalPins: [4 7 8 9 10 11 14 15 17 18 22 23 24 25 27 30 31]
    AvailableSPIChannels: {}
      AvailableI2CBuses: {'i2c-0'  'i2c-1'}
             I2CBusSpeed: 100000

  Supported peripherals

Redisplay AvailableI2CBuses and I2CBusSpeed.

mypi.AvailableI2CBuses
mypi.I2CBusSpeed      

ans =

  1×2 cell array 

    {'i2c-0'}    {'i2c-1'}

ans =

      100000

Show the location of the I2C pins.

showPins(mypi)

The pin map shows that, for this model and revision of the board, the i2c-1 bus is available on the GPIO header pins I2C1_SDA (GPIO 2) and I2C1_SCL (GPIO 3).

After physically connecting your I2C device to the I2C pins, get the addresses of I2C devices attached to the I2C bus, 'i2c-1'.

scanI2CBus(mypi,'i2c-1')

ans = 

     {'0x55','0x20'}

Create a connection, i2csensor, from the MATLAB software to the I2C sensor at '0x20'.

i2csensor = i2cdev(mypi,'i2c-1','0x20')

i2csensor = 

I2C with Properties:
     Bus: i2c-1
    I2CAddress: 0x20

Read two uint8 numbers from the sensor.

output1 = read(i2csensor,2)

Read the value of register 14 from the sensor.

output2 = readRegister(i2csensor,14)

Create a connection, i2cdisplay, from the MATLAB software to the I2C LED display at '0x55'.

i2cdisplay = i2cdev(mypi,'i2c-1','0x55')

i2cdisplay = 

I2C with Properties:
     Bus: i2c-1
    I2CAddress: 0x55

Write characters to the display.

write(i2cdisplay,[hex2dec('20') hex2dec('51')])

Write a scalar hexadecimal value, hex2dec('08'), to register 3 on an I2C device.

writeRegister(i2cdisplay,3,hex2dec('08'),'uint8')

If you are not using I2C, disable I2C to free additional GPIO pins.

disableI2C(mypi)

Before using I2C again, enable I2C.

enableI2C(mypi)

When you enable I2C, you can change the mypi.I2CBusSpeed property.

disableI2C(mypi)
enableI2C(mypi,400000)
mypi.I2CBusSpeed

ans =

       40000

Input Arguments

mypi — Connection to specific Raspberry Pi hardware board

raspi object

Connection to a specific Raspberry Pi hardware board, specified as a raspi object.

i2cBusSpeed — I2C bus speed

100000 (default) | 400000

I2C bus speed, specified as a scalar.

Example: 100000

Data Types: double