the I2C communication has been modified several times in the past, which caused incompatibilities and confusion when programming classes for the I2C extension chips PCF8574 and PCF8591. After some testing I found out that my classes still work with release 0.90. So if you need such classes and don't want to evaluate several older classes yourself, use these:
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import lejos.nxt.I2CPort;
/**
* Access to a PCF8574 chip, which is a parallel port extension via I2C.
* @author Stefan Frings
*/
public class PCF8574 {
/** Port where the chip is attached to */
private final I2CPort port;
/** Device address of the chip */
private final int address;
/** Buffer for i/o */
private byte buffer[]={0};
/**
* Constructor
* @param i2cPort Port wheere the chip is attached to (e.g. SensorPort.S1)
* @param deviceAddress Device address of the chip (e.g. 0x40)
*/
public PCF8574(I2CPort i2cPort, int deviceAddress) {
port=i2cPort;
address=deviceAddress;
port.i2cEnable(I2CPort.STANDARD_MODE);
}
/**
* Write to the i/o pins
* @param value Data to be written
*/
public void write(byte value) {
buffer[0]=value;
port.i2cTransaction(address,buffer,0,1,null,0,0);
}
/**
* Read from the i/o pins
* @return Data that have been read
*/
public byte read() {
port.i2cTransaction(address,null,0,0,buffer,0,1);
return buffer[0];
}
}
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import lejos.nxt.I2CPort;
/**
* Access to a PCF8591 chip, which is an analog port extension via I2C.
* @author Stefan Frings
*/
public class PCF8591 {
/** Port where the chip is attached to */
private final I2CPort port;
/** Device address of the chip */
private final int address;
/** Buffer for i/o */
private byte buffer[]={0,0,0,0,0};
/** Operational mode */
private byte mode;
/** Standard mode: four single-ended inputs */
public static final byte MODE_STANDARD=0;
/** Three differential mode: input 3 gets subtracted from input 0,1 and 2 */
public static final byte MODE_THREE_DIFFERENTIAL=1;
/** Mixed mode: input 0 and 1 are single-ended inputs, input 3 gets subtracted from input 2 */
public static final byte MODE_MIXED=2;
/** Dual differential mode: input 1 is subtracted from input 0, input 3 is subtracted fom input 2 */
public static final byte MODE_DUAL_DIFFENRENTIAL=3;
/**
* Constructor
* @param i2cPort Port wheere the chip is attached to (e.g. SensorPort.S1)
* @param deviceAddress Device address of the chip (e.g. 0x90)
* @param mode Operational mode of the analog inputs, see MODE_XXX constants
*/
public PCF8591(I2CPort i2cPort, int deviceAddress, byte mode) {
port=i2cPort;
address=deviceAddress;
this.mode=0;
port.i2cEnable(I2CPort.STANDARD_MODE);
}
/**
* Write a byte to the analog output
* @param value Data to be written
*/
public void write(byte value) {
buffer[0]=(byte) (0x40+(mode<<4));
buffer[1]=value;
port.i2cTransaction(address,buffer,0,2,null,0,0);
}
/**
* Read from a single analog input
* @param channel Channel number (0-3)
* @return Data from the A/D converter
*/
public byte read(byte channel) {
buffer[0]=(byte) (0x40+(mode<<4)+channel);
port.i2cTransaction(address,buffer,0,1,buffer,0,2);
return buffer[1];
}
/**
* Read from all analog inputs
* @return Data from the A/D converter, 4 bytes
*/
public byte[] read() {
buffer[0]=(byte) (0x44+(mode<<4));
port.i2cTransaction(address,buffer,0,1,buffer,0,5);
// copy and shift buffered data because the first byte is not useable
byte[] result=new byte[4];
result[0]=buffer[1];
result[1]=buffer[2];
result[2]=buffer[3];
result[3]=buffer[4];
return result;
}
}