Package com.pi4j.wiringpi

Class Spi

java.lang.Object

com.pi4j.wiringpi.Spi

public class Spi
extends Object

WiringPi includes a library which can make it easier to use the Raspberry Pi’s on-board SPI interface.

Before you can use SPI interface, you may need to use the gpio utility to load the SPI drivers into the kernel:

$ gpio load spi

If you need a buffer size of greater than 4KB, then you can specify the size (in KB) on the command line:

$ gpio load spi 100

will allocate a 100KB buffer. (You should rarely need this though, the default is more than enough for most applications).

This library depends on the wiringPi native system library. (developed by Gordon Henderson @ http://wiringpi.com)

Author:

Robert Savage (http://www.savagehomeautomation.com)

See Also:

https://www.pi4j.com/, http://wiringpi.com/reference/spi-library

Field Summary

Fields

Modifier and Type	Field	Description
static int	CHANNEL_0
static int	CHANNEL_1
static int	MODE_0
static int	MODE_1
static int	MODE_2
static int	MODE_3

Method Summary

Modifier and Type	Method	Description
static int	wiringPiSPIDataRW(int channel, byte[] data)	wiringPiSPIDataRW:
static int	wiringPiSPIDataRW(int channel, byte[] data, int len)	wiringPiSPIDataRW:
static int	wiringPiSPIDataRW(int channel, short[] data)	wiringPiSPIDataRW:
static int	wiringPiSPIDataRW(int channel, short[] data, int len)	wiringPiSPIDataRW:
static int	wiringPiSPIDataRW(int channel, String data)	wiringPiSPIDataRW:
static int	wiringPiSPIDataRW(int channel, String data, int len)	wiringPiSPIDataRW:
static int	wiringPiSPIGetFd(int channel)	wiringPiSPIGetFd:
static int	wiringPiSPISetup(int channel, int speed)	wiringPiSPISetup:
static int	wiringPiSPISetupMode(int channel, int speed, int mode)	wiringPiSPISetupMode:

Methods inherited from class java.lang.Object

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

Field Detail

CHANNEL_0

public static int CHANNEL_0

CHANNEL_1

public static int CHANNEL_1

MODE_0

public static int MODE_0

MODE_1

public static int MODE_1

MODE_2

public static int MODE_2

MODE_3

public static int MODE_3

Method Detail

wiringPiSPISetup

public static int wiringPiSPISetup(int channel,
                                   int speed)

wiringPiSPISetup:

This is the way to initialise a channel (The Pi has 2 channels; 0 and 1). The speed parameter is an integer in the range 500,000 through 32,000,000 and represents the SPI clock speed in Hz.

The returned value is the Linux file-descriptor for the device, or -1 on error. If an error has happened, you may use the standard errno global variable to see why.

Parameters:

channel - SPI channel

speed - SPI speed

Returns:

return -1 on error

See Also:

http://wiringpi.com/reference/spi-library

wiringPiSPISetupMode

public static int wiringPiSPISetupMode(int channel,
                                       int speed,
                                       int mode)

wiringPiSPISetupMode:

This is the way to initialise a channel (The Pi has 2 channels; 0 and 1). The speed parameter is an integer in the range 500,000 through 32,000,000 and represents the SPI clock speed in Hz.

The returned value is the Linux file-descriptor for the device, or -1 on error. If an error has happened, you may use the standard errno global variable to see why.

Parameters:

channel - SPI channel

speed - SPI speed

mode - SPI mode (Mode is 0, 1, 2 or 3; see http://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus#Mode_numbers)

Returns:

return -1 on error

See Also:

http://wiringpi.com/reference/spi-library, http://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus#Mode_numbers

wiringPiSPIGetFd

public static int wiringPiSPIGetFd(int channel)

wiringPiSPIGetFd:

Return the file-descriptor for the given channel

Parameters:

channel - SPI channel

Returns:

file-descriptor for the given channel

See Also:

http://wiringpi.com/reference/spi-library

wiringPiSPIDataRW

public static int wiringPiSPIDataRW(int channel,
                                    String data)

wiringPiSPIDataRW:

This performs a simultaneous write/read transaction over the selected SPI bus. Data that was in your buffer is overwritten by data returned from the SPI bus.

(ATTENTION: the 'data' argument can only be a maximum of 1024 characters.)

Parameters:

channel - SPI channel

data - string data payload

Returns:

return -1 on error

See Also:

http://wiringpi.com/reference/spi-library

wiringPiSPIDataRW

public static int wiringPiSPIDataRW(int channel,
                                    String data,
                                    int len)

wiringPiSPIDataRW:

This performs a simultaneous write/read transaction over the selected SPI bus. Data that was in your buffer is overwritten by data returned from the SPI bus.

(ATTENTION: the 'data' argument can only be a maximum of 1024 characters.)

Parameters:

channel - SPI channel

data - string data payload

len - length of characters in string (must be total string length, not a substring)

Returns:

return -1 on error

See Also:

http://wiringpi.com/reference/spi-library

wiringPiSPIDataRW

public static int wiringPiSPIDataRW(int channel,
                                    byte[] data,
                                    int len)

wiringPiSPIDataRW:

This performs a simultaneous write/read transaction over the selected SPI bus. Data that was in your buffer is overwritten by data returned from the SPI bus.

(ATTENTION: the 'data' argument can only be a maximum of 1024 characters.)

Parameters:

channel - SPI channel

data - byte array data payload

len - length of bytes in data array argument

Returns:

return -1 on error

See Also:

http://wiringpi.com/reference/spi-library

wiringPiSPIDataRW

public static int wiringPiSPIDataRW(int channel,
                                    byte[] data)

wiringPiSPIDataRW:

This performs a simultaneous write/read transaction over the selected SPI bus. Data that was in your buffer is overwritten by data returned from the SPI bus.

(ATTENTION: the 'data' argument can only be a maximum of 1024 characters.)

Parameters:

channel - SPI channel

data - byte array data payload

Returns:

return -1 on error

See Also:

http://wiringpi.com/reference/spi-library

wiringPiSPIDataRW

public static int wiringPiSPIDataRW(int channel,
                                    short[] data,
                                    int len)

wiringPiSPIDataRW:

This performs a simultaneous write/read transaction over the selected SPI bus. The data argument is passed into the wiringPI function as the argument and the output from Spi is returned by this method

Parameters:

channel - SPI channel

data - short array data payload. Note that wiringPi uses unsigned char for the data transmission. That is 8-bit. in other words values 0-255. So make sure the values in data do not exceed this range, otherwise the numbers would overflow in the native code and unexpected results would yield

len - length of bytes in data array argument

Returns:

return -1 on error

See Also:

http://wiringpi.com/reference/spi-library

wiringPiSPIDataRW

public static int wiringPiSPIDataRW(int channel,
                                    short[] data)

wiringPiSPIDataRW:

This performs a simultaneous write/read transaction over the selected SPI bus. The data argument is passed into the wiringPI function as the argument and the output from Spi is returned by this method

Parameters:

channel - SPI channel

data - short array data payload. Note that wiringPi uses unsigned char for the data transmission. That is 8-bit. in other words values 0-255. So make sure the values in data do not exceed this range, otherwise the numbers would overflow in the native code and unexpected results would yield

Returns:

return -1 on error

See Also:

http://wiringpi.com/reference/spi-library