spidev

Connection to SPI device on Raspberry Pi hardware

Description

This object represents a connection from the MATLAB^® software to the SPI device on the Raspberry Pi™ hardware. To exchange data with the SPI device, use this object with the functions listed in Object Functions.

Creation

Syntax

myspidevice = spidev(mypi,channel)

myspidevice = spidev(mypi,channel,mode,speed,BitsPerWord)

Description

myspidevice = spidev(mypi,channel) creates a connection, myspidevice, from the MATLAB software to the chip select pin, Channel, of the SPI device on the Raspberry Pi hardware.

myspidevice = spidev(mypi,channel,mode,speed,BitsPerWord) sets one or more of the optional Mode, Speed, and BitsPerWord properties.

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.

Properties

Channel — SPI communication channel

'CE0' | 'CE1'

This property is read-only.

The SPI channel on the hardware for communication, specified as a character vector. This property is set by the channel input argument. It cannot be changed after object creation

Example: 'CE0'

Data Types: char

Mode — SPI communication mode

0 (default) | 1 | 2 | 3

This property is read-only.

The mode of SPI communication used by the SPI bus, specified as a number between 0 and 3. The mode is defined by clock polarity (CPOL) and phase (CPHA) values.

Mode	CPOL	CPHA
0	0	0
1	0	1
2	1	0
3	1	1

This property is set by the mode input argument. If not specified as an input argument, it takes the default value. It cannot be changed after object creation.

Example: 0

Data Types: double

BitsPerWord — SPI bits per word

8

This property is read-only.

The number of SPI bits per word, specified as a scalar.

Example: 8

Data Types: double

Speed — SPI communication speed

500000 | 1000000 | 2000000 | 4000000 | 8000000 | 16000000 | 32000000

This property is read-only.

Speed of SPI communication (clock cycles) in Hertz, specified as a scalar. This property is set by the speed input argument. If not specified as an input argument, it takes the default value. It cannot be changed after object creation.

Example: 500000

Data Types: double

Object Functions

writeRead

Write data to and read data from SPI device

Examples

Connect to and Exchange Data with SPI Devices

You can connect to and exchange data with an SPI device.

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

mypi = raspi

r = 

  raspi with properties:

         DeviceAddress: '172.18.188.249'              
                  Port: 18734                         
             BoardName: 'Raspberry Pi 3 Model B+'     
         AvailableLEDs: {'led0'}                      
  AvailableDigitalPins: [4,5,6,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27]
  AvailableSPIChannels: {'CE0','CE1'}                 
     AvailableI2CBuses: {'i2c-1'}                     
      AvailableWebcams: {}                            
           I2CBusSpeed: 100000                        

  Supported peripherals

By default, SPI is enabled. If SPI is disabled, AvailableSPIChannels does not show any channels.

Enable SPI and get the channels by using enableSPI.

enableSPI(mypi)
mypi.AvailableSPIChannels

ans = 

    'CE0'    'CE1'

Show the location of the SPI pins, GPIO 10 (SPI0_MOSI), GPIO 9 (SPI0_MISO), and GPIO 11 (SPI0_SCLK), on the GPIO header.

showPins(mypi)

After physically connecting your SPI device to the three SPI pins, connect to the SPI device.

myspidevice = spidev(mypi,'CE1',0)

myspidevice = 

Spidev with Properties:
           Channel: 'CE1'
              Mode: 0 
       BitsPerWord: 8
             Speed: 500000

Write data to, and read data from, the SPI device.

out = writeRead(myspidevice,[hex2dec('08') hex2dec('D4')])

out = 
         7 211

If you are not using SPI, disable SPI to make additional GPIO pins available.

disableSPI(mypi)

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

• You can also deploy spidev on the Raspberry Pi hardware in MATLAB Online™.