com.pi4j.wiringpi

Class Spi

java.lang.Object

com.pi4j.wiringpi.Spi

public class Spi
extends Object

WiringPi includes a software-driven PWM handler capable of outputting a PWM signal on any of the Raspberry Pi's GPIO pins.

There are some limitations. To maintain a low CPU usage, the minimum pulse width is 100uS. That combined with the default suggested range of 100 gives a PWM frequency of 100Hz. You can lower the range to get a higher frequency, at the expense of resolution, or increase to get more resolution, but that will lower the frequency. If you change the pulse-width in the drive code, then be aware that at delays of less than 100uS wiringPi does it in a software loop, which means that CPU usage will rise dramatically, and controlling more than one pin will be almost impossible.

Also note that while the routines run themselves at a higher and real-time priority, Linux can still affect the accuracy of the generated signal.

However, within these limitations, control of a light/LED or a motor is very achievable.

You must initialize wiringPi with one of wiringPiSetup() or wiringPiSetupGpio() functions beforehand. wiringPiSetupSys() is not fast enough, so you must run your programs with sudo.

Before using the Pi4J library, you need to ensure that the Java VM in configured with access to the following system libraries:

• pi4j
• wiringPi
• pthread

This library depends on the wiringPi native system library.
(developed by Gordon Henderson @ https://projects.drogon.net/)

Author:

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

See Also:

http://www.pi4j.com/

Field Summary

Fields

Modifier and Type	Field and Description
static int	CHANNEL_0
static int	CHANNEL_1

Method Summary

Methods

Modifier and Type	Method and Description
static int	wiringPiSPIDataRW(int channel, byte[] data, int len) 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:

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

Method Detail

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

wiringPiSPIDataRW

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

wiringPiSPIDataRW:

Write and Read a block of data over the SPI bus. Note the data is being read into the transmit buffer, so will overwrite it! This is also a full-duplex operation.

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

Parameters:

channel - SPI channel

data -

len -

Returns:

return -1 on error

wiringPiSPIDataRW

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

wiringPiSPIDataRW:

Write and Read a block of data over the SPI bus. Note the data is being read into the transmit buffer, so will overwrite it! This is also a full-duplex operation.

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

Parameters:

channel - SPI channel

data -

len -

Returns:

return -1 on error

wiringPiSPISetup

public static int wiringPiSPISetup(int channel,
                   int speed)

wiringPiSPISetup:

Open the SPI device, and set it up, etc.

Parameters:

channel - SPI channel

speed - SPI speed

Returns:

return -1 on error