Class LinuxFsSpi

java.lang.Object

com.pi4j.common.IdentityBase

com.pi4j.io.IOBase<Spi, SpiConfig, SpiProvider>

com.pi4j.io.spi.SpiBase

com.pi4j.plugin.linuxfs.provider.spi.LinuxFsSpi

All Implemented Interfaces:

Describable, Identity, Lifecycle, Extension, IO<Spi, SpiConfig, SpiProvider>, IODataReader, IODataWriter, Spi, AutoCloseable, Readable

public class LinuxFsSpi
extends SpiBase
implements Spi

SPI implementation that uses JNA bindings to the Linux SPI device (i.e. /dev/spidev0.0). Only supports writing but it works to drive an SSD1306 OLED display.

Since:

10/3/24.

Author:

mpilone

See Also:

• spi-c-ioctl
• spidev.h
• spi.h
• spidev_fdx.c
• SPI userspace API

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	LinuxFsSpi.spi_ioc_transfer

Field Summary

Fields inherited from class com.pi4j.io.spi.SpiBase

isOpen

Fields inherited from class com.pi4j.io.IOBase

config, provider

Fields inherited from class com.pi4j.common.IdentityBase

description, id, metadata, name

Fields inherited from interface com.pi4j.io.spi.Spi

DEFAULT_BAUD, DEFAULT_BUS, DEFAULT_CHIP_SELECT, DEFAULT_MODE, DEFAULT_READ_LSB_FIRST, DEFAULT_WRITE_LSB_FIRST

Constructor Summary

Constructors

Constructor	Description
LinuxFsSpi(LinuxFsSpiProviderImpl provider, SpiConfig config)

Method Summary

Modifier and Type	Method	Description
void	close()
void	open()
int	read()
int	read(byte[] read, int offset, int length)
int	transfer(byte[] write, int writeOffset, byte[] read, int readOffset, int numberOfBytes)
int	write(byte b)
int	write(byte[] data, int offset, int length)	write SPI_BUFFSIZ most often is set to 4096.

Methods inherited from class com.pi4j.io.spi.SpiBase

isOpen

Methods inherited from class com.pi4j.io.IOBase

config, context, describe, description, initialize, name, provider, shutdown

Methods inherited from class com.pi4j.common.IdentityBase

description, id, metadata, name

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface com.pi4j.common.Identity

description, getDescription, getId, getMetadata, getName, id, metadata, name

Methods inherited from interface com.pi4j.io.IO

config, description, name, provider, type

Methods inherited from interface com.pi4j.io.IODataReader

getInputStream, in, read, read, read, read, read, read, read, read, read, read, read, read, read, read, read, read, read, readByte, readByteBuffer, readByteBuffer, readCharArray, readCharArray, readCharArray, readCharArray, readCharBuffer, readCharBuffer, readCharBuffer, readCharBuffer, readNBytes, readNBytes, readString, readString, readString, readString

Methods inherited from interface com.pi4j.io.IODataWriter

getOutputStream, out, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write

Methods inherited from interface com.pi4j.common.Lifecycle

initialize, shutdown

Methods inherited from interface com.pi4j.io.spi.Spi

isOpen, transfer, transfer, transfer, transfer, transfer, transfer, transfer, transfer, transferByte

Constructor Details

LinuxFsSpi

public LinuxFsSpi(LinuxFsSpiProviderImpl provider,
 SpiConfig config)

Method Details

open

public void open()

Specified by:

open in interface Spi

Overrides:

open in class SpiBase

close

public void close()

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Spi

Overrides:

close in class SpiBase

transfer

public int transfer(byte[] write,
 int writeOffset,
 byte[] read,
 int readOffset,
 int numberOfBytes)

Specified by:

transfer in interface Spi

read

public int read()

Specified by:

read in interface IODataReader

read

public int read(byte[] read,
 int offset,
 int length)

Specified by:

read in interface IODataReader

write

public int write(byte b)

Specified by:

write in interface IODataWriter

write

public int write(byte[] data,
 int offset,
 int length)

write SPI_BUFFSIZ most often is set to 4096. See initialize() This implementation can write blocks greater than 4096 byte 'however', read and understand how this is accomplished. A write of data no greater than 4096 bytes is accomplished with a single SPI write operation. So CE line low, write bytes, CE line high A write greater than 4096 bytes will be segmented to multiple writes each 4096 bytes in length, the last write is the MOD value. So, CE line low, write first 4096 bytes CE line high. This pattern will repeat until the last bytes length MOD 4096 are written. This means multiple SPI transaction with you SPI device. If CE line toggling creates problems with your SPI device your application can use a vacant GPIO configured as an Output pin and your application keep the CE pin low during the duration of the call to spi,write.

Specified by:

write in interface IODataWriter

Parameters:

data - data array of bytes to be written

offset - offset in data buffer to start at

length - number of bytes to be written

Returns: