com.pi4j.wiringpi

Class Gertboard

java.lang.Object

com.pi4j.wiringpi.Gertboard

public class Gertboard
extends Object

The Gertboard has an on-board Digital to Analog (DAC) converter and an Analog to Digital (ADC) converters. These are connected via the SPI bus back to the Raspberry Pi host.

Each of the DAC and ADC chips has 2 channels.

The DAC has a resolution of 8 bits and produces an output voltage between 0 and 2.047 volts, the ADC has a resolution of 10 bits and can take an input voltage between 0 and 3.3 volts.

Part of the wiringPi library includes code to setup and drive these chips in an easy to use manner.

To use in a program, first you need to make sure that the 5 SPI jumpers are present on the Gertboard (there are 7 in total, 5 for the SPI, 2 to connect the serial to the ATmega), the photo below shows all 7 jumpers in-place.

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

• pi4j
• wiringPi

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/dev-lib/gertboard-analog/

Field Summary

Fields

Modifier and Type	Field and Description
static int	SPI_A2D
static int	SPI_ADC_SPEED
static int	SPI_D2A
static int	SPI_DAC_SPEED

Method Summary

Modifier and Type	Method and Description
static int	gertboardAnalogRead(int chan) This returns a value from 0 to 1023 representing the value on the supplied channel (0 or 1).
static int	gertboardAnalogSetup(int pinBase) This setup routine allocates 2 pins and overlays the analog to digital input pins with the digital to analog output pins.
static void	gertboardAnalogWrite(int chan, int value) This outputs the supplied value (0-255) to the given channel (0 or 1).
static int	gertboardSPISetup() This must be called to initialize the SPI bus to communicate with the Gertboards ADC and DAC chips.

Methods inherited from class java.lang.Object

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

Field Detail

SPI_ADC_SPEED

public static final int SPI_ADC_SPEED

See Also:

Constant Field Values

SPI_DAC_SPEED

public static final int SPI_DAC_SPEED

See Also:

Constant Field Values

SPI_A2D

public static final int SPI_A2D

See Also:

Constant Field Values

SPI_D2A

public static final int SPI_D2A

See Also:

Constant Field Values

Method Detail

gertboardAnalogWrite

public static void gertboardAnalogWrite(int chan,
                                        int value)

This outputs the supplied value (0-255) to the given channel (0 or 1). The output voltage is:

 vOut = value / 255 * 2.047
 

or to find the value for a given voltage:

 value = vOut / 2.047 * 255
 

Parameters:

chan - Analog channel to write to (0 or 1).

value - The output value (0-255) supplied to the given channel (0 or 1).

See Also:

http://wiringpi.com/dev-lib/gertboard-analog/

gertboardAnalogRead

public static int gertboardAnalogRead(int chan)

This returns a value from 0 to 1023 representing the value on the supplied channel (0 or 1). To convert this to a voltage, use the following formula:

 vIn = value * 3.3 / 1023
 

Parameters:

chan - Analog channel to read from (0 or 1).

Returns:

This returns a value from 0 to 1023 representing the value on the supplied channel (0 or 1).

See Also:

http://wiringpi.com/dev-lib/gertboard-analog/

gertboardSPISetup

public static int gertboardSPISetup()

This must be called to initialize the SPI bus to communicate with the Gertboards ADC and DAC chips. If the return value is < 0 then an error occurred and errno will be set appropriately.

Returns:

If the return value is < 0 then an error occurred and errno will be set appropriately. If the return value is '0' or greater than the call was successful.

See Also:

http://wiringpi.com/dev-lib/gertboard-analog/

gertboardAnalogSetup

public static int gertboardAnalogSetup(int pinBase)

This setup routine allocates 2 pins and overlays the analog to digital input pins with the digital to analog output pins. So reading channel pinBase + 0 reads the first analog input channel (pin DA0 on the Gertboard), and writing pinBase + 0 outputs to the first analog output channel. (Pin AD0).

Parameters:

pinBase - pinBase is the base pin that you want the analog ports to appear as

Returns:

If the return value is < 0 then an error occurred and errno will be set appropriately. If the return value is '0' or greater than the call was successful.

See Also:

http://wiringpi.com/dev-lib/gertboard-analog/