com.raspoid.additionalcomponents.adc

Class PCF8591

java.lang.Object

com.raspoid.I2CComponent

com.raspoid.additionalcomponents.adc.PCF8591

All Implemented Interfaces:

ADC, Component

public class PCF8591
extends I2CComponent
implements ADC

Implementation of the ADC (Analog to Digital Converter) PCF8591.

Some specifications:

• Four analog inputs.
• One analog output.
• A serial I2C-bus interface.
• Three address pins A0, A1 and A2 (up to eight devices connected to the i2c bus without additional hardware).

Address, control and data to and from the device are transfered serially via the two-line bidirectional I2C-bus.

! NOTE ! known bug when reading digital values from PCF8591 if analog output disabled ! (independent of this framework)

Datasheet: PCF8591

Each PCF8591 device in an I2C-bus system is activated by sending a valid address to the device. The address (8 bits) consists of a fixed part (4 bits), a programmable part (3 bits) and a read/write-bit (1 bit) which sets the direction of the following data transfer.

• Programmable part: set according to the address pins A0, A1 and A2.
• The address: always the first byte sent after the start condition in the I2C-bus protocol.

Example of use: PCF8591Example

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	PCF8591.AnalogueInputProgrammingMode There exists 4 different modes to deal with the four analog inputs.

Field Summary

Fields

Modifier and Type	Field and Description
static byte	ANALOGUE_OUTPUT_ENABLE_FLAG Analog output active if bit at position 2 in control byte is 1.
static byte	AUTO_INCREMENT_FLAG If the auto-increment flag is set to 1, the channel number is incremented automatically after each A/D conversion.
static PCF8591InputChannel	CHANNEL_0 A/D channel 0.
static PCF8591InputChannel	CHANNEL_1 A/D channel 1.
static PCF8591InputChannel	CHANNEL_2 A/D channel 2.
static PCF8591InputChannel	CHANNEL_3 A/D channel 3.
static int	DEFAULT_PCF8591_ADDRESS Default i2c PCF8591 address.

Fields inherited from class com.raspoid.I2CComponent

device, MAX_I2C_ADDRESS, MIN_I2C_ADDRESS

Constructor Summary

Constructors

Constructor and Description
PCF8591() Default constructor for a PCF8591 using the default i2c address of the component, the four single ended analogue input programming mode, enabling the analog output and disabling the auto increment flag.
PCF8591(int i2cAddress, PCF8591.AnalogueInputProgrammingMode mode, boolean enableAnalogOutput, boolean enableAutoIncrement) Constructor for a PCF8591 using a specific i2c address, a specific analog input programming mode, a specific boolean to enable/disable the analogue output of the PCF8591 and a specific value for the auto increment flag.

Method Summary

Modifier and Type	Method and Description
int	analogToDigital(ADCChannel inputChannel) Read a digital value from the ADC through I2C.
int	analogToDigital(PCF8591InputChannel inputChannel) Read a digital value from the PCF8591 through i2c.
void	digitalToAnalog(int value) Send a digital value to the PCF8591 through i2c.
java.lang.String	toString()

Methods inherited from class com.raspoid.I2CComponent

getDevice, getType, readSignedRegisterValue, readTwoSignedRegsiters, readTwoUnsignedRegisters, readUnsignedRegisterValue, writeUnsignedValueDirectlyToI2CDevice, writeUnsignedValueToRegister

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_PCF8591_ADDRESS

public static final int DEFAULT_PCF8591_ADDRESS

Default i2c PCF8591 address.

See Also:

Constant Field Values

ANALOGUE_OUTPUT_ENABLE_FLAG

public static final byte ANALOGUE_OUTPUT_ENABLE_FLAG

Analog output active if bit at position 2 in control byte is 1.

See Also:

Constant Field Values

AUTO_INCREMENT_FLAG

public static final byte AUTO_INCREMENT_FLAG

If the auto-increment flag is set to 1, the channel number is incremented automatically after each A/D conversion.

See Also:

Constant Field Values

CHANNEL_0

public static final PCF8591InputChannel CHANNEL_0

A/D channel 0.

Note: the output of each channel depends on the mode selected for the analogue input progamming.

See Also:

CHANNEL_1, CHANNEL_2, CHANNEL_3

CHANNEL_1

public static final PCF8591InputChannel CHANNEL_1

A/D channel 1.

Note: the output of each channel depends on the mode selected for the analogue input progamming.

See Also:

CHANNEL_0, CHANNEL_2, CHANNEL_3

CHANNEL_2

public static final PCF8591InputChannel CHANNEL_2

A/D channel 2.

Note: the output of each channel depends on the mode selected for the analogue input progamming.

See Also:

CHANNEL_0, CHANNEL_1, CHANNEL_3

CHANNEL_3

public static final PCF8591InputChannel CHANNEL_3

A/D channel 3.

Note: the output of each channel depends on the mode selected for the analogue input progamming.

See Also:

CHANNEL_0, CHANNEL_1, CHANNEL_2

Constructor Detail

PCF8591

public PCF8591()

Default constructor for a PCF8591 using the default i2c address of the component, the four single ended analogue input programming mode, enabling the analog output and disabling the auto increment flag.

PCF8591

public PCF8591(int i2cAddress,
               PCF8591.AnalogueInputProgrammingMode mode,
               boolean enableAnalogOutput,
               boolean enableAutoIncrement)

Constructor for a PCF8591 using a specific i2c address, a specific analog input programming mode, a specific boolean to enable/disable the analogue output of the PCF8591 and a specific value for the auto increment flag.

Parameters:

i2cAddress - the i2c address of the PCF8591.

mode - the selected analog input programming mode.

enableAnalogOutput - true to enable the analog output of the PCF8591 (/!\ pay attention to bug described in class header (PCF8591)). False to disable.

enableAutoIncrement - true to enable the auto increment flag. False to disable.

Method Detail

analogToDigital

public int analogToDigital(ADCChannel inputChannel)

Description copied from interface: ADC

Read a digital value from the ADC through I2C.

Specified by:

analogToDigital in interface ADC

Parameters:

inputChannel - the input channel on the ADC from which to read the data.

Returns:

the int representation of the newly read value from the specified analog input channel.

analogToDigital

public int analogToDigital(PCF8591InputChannel inputChannel)

Read a digital value from the PCF8591 through i2c.

Note:

• readBuffer[0] contains the previous digital value.
• readBuffer[1] contains the new digital value.

[datasheet] The first byte transmitted in a read cycle contains the conversion result code of the previous read cycle. After a POR condition, the first byte read is 80h.

Parameters:

inputChannel - the input channel on the PCF8591 from which to read the data.

Returns:

the int representation of the newly read value from the specified analog input channel.

digitalToAnalog

public void digitalToAnalog(int value)

Send a digital value to the PCF8591 through i2c.

This value will be converted in an analog signal by the PCF8591, and this signal will output on the AOUT pin.

Note: the led on the sunfounder PCF8591 custom board will shine accordingly to the analog output voltage (led won't light up below 125).

[datasheet - p.7] The third byte sent to a PCF8591 device is stored in the DAC data register and is converted to the corresponding analog voltage using the on-chip D/A converter.

[datasheet - p.5-7] protocol: for D/A conversion, after the addressing byte, send the control byte and then the data byte. Note: we use a buffer to send the two consecutive bytes ! (otherwise: bug)

Parameters:

value - the data value to send on the analog output, in the 0..255 range.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object