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SPI.java
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/* -*- mode: java; c-basic-offset: 2; indent-tabs-mode: nil -*- */
/*
Copyright (c) The Processing Foundation 2015
Hardware I/O library developed by Gottfried Haider as part of GSoC 2015
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General
Public License along with this library; if not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330,
Boston, MA 02111-1307 USA
*/
package processing.io;
import processing.io.NativeInterface;
import java.io.File;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
/**
* Opens an SPI interface as master<br/>
* </br>
* Serial Peripheral Interface (SPI) is a serial bus, commonly used to
* communicate with sensors and memory devices. It uses four pins: MOSI (Master
* Out Slave In), MISO (Master In Slave Out), and SCLK (clock signal) - those
* three are shared among all devices on the bus - as well as one or more SS
* (Slave Select) pins, that are used for the master to signal to the slave
* device that it is the desired respondent for the transmission.<br/>
* <br/>
* The "master" device initiates a transfer by pulling the SS pin of the "slave"
* low, and begins outputting a clock signal. In SPI, both the "master" as well
* as the "slave" device output data at the same time. It is hence not possible
* to read data without writing some (even if it means outputting zeros or other
* dummy data).</br>
* </br>
* There are multiple possible configuration settings for SPI, see
* <a href="SPI_settings_.html">settings()</a> for details.</br>
* <br/>
* This library supports multiple SPI objects making use of the same SPI
* interface.
*
* @webref SPI
* @webBrief Opens an SPI interface as master
*/
public class SPI {
/**
* CPOL=0, CPHA=0, most common
*/
public static final int MODE0 = 0;
/**
* CPOL=0, CPHA=1
*/
public static final int MODE1 = 1;
/**
* CPOL=1, CPHA=0
*/
public static final int MODE2 = 2;
/**
* CPOL=1, CPHA=1
*/
public static final int MODE3 = 3;
/**
* most significant bit first, most common
*/
public static final int MSBFIRST = 0;
/**
* least significant bit first
*/
public static final int LSBFIRST = 1;
protected int dataOrder = 0;
protected String dev;
protected int handle;
protected int maxSpeed = 500000;
protected int mode = 0;
protected static Map<String, String> settings = new HashMap<String, String>();
/**
* Opens an SPI interface as master
* @param dev device name
* @see list
* @webref SPI
* @webBrief Opens an SPI interface as master
*/
public SPI(String dev) {
NativeInterface.loadLibrary();
this.dev = dev;
if (NativeInterface.isSimulated()) {
return;
}
handle = NativeInterface.openDevice("/dev/" + dev);
if (handle < 0) {
throw new RuntimeException(NativeInterface.getError(handle));
}
}
/**
* Closes the SPI interface</br>
* </br>
* It is normally not necessary to explicitly close SPI interfaces, as they are
* closed automatically by the operating system when the sketch exits.</br>
* </br>
* Note: It is possible to have two or more objects using the same interface at
* a time.
*
* @webref SPI
* @webBrief Closes the SPI interface
*/
public void close() {
if (NativeInterface.isSimulated()) {
return;
}
NativeInterface.closeDevice(handle);
handle = 0;
}
protected void finalize() throws Throwable {
try {
close();
} finally {
super.finalize();
}
}
/**
* Lists all available SPI interfaces
* @return String array
* @webref SPI
* @webBrief Lists all available SPI interfaces
*/
public static String[] list() {
if (NativeInterface.isSimulated()) {
// as on the Raspberry Pi
return new String[]{ "spidev0.0", "spidev0.1" };
}
ArrayList<String> devs = new ArrayList<String>();
File dir = new File("/dev");
File[] files = dir.listFiles();
if (files != null) {
for (File file : files) {
if (file.getName().startsWith("spidev")) {
devs.add(file.getName());
}
}
}
// listFiles() does not guarantee ordering
String[] tmp = devs.toArray(new String[devs.size()]);
Arrays.sort(tmp);
return tmp;
}
/**
* Configures the SPI interface<br/>
* <br/>
* The default setting is: 500000, SPI.MSBFIRST, SPI.MODE0
*
* @param maxSpeed maximum transmission rate in Hz, 500000 (500 kHz) is a
* resonable default
* @param dataOrder whether data is send with the first- or least-significant
* bit first (SPI.MSBFIRST or SPI.LSBFIRST, the former is more
* common)
* @param mode <a href=
* "https://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus#Clock_polarity_and_phase">SPI.MODE0
* to SPI.MODE3</a>
* @webref SPI
* @webBrief Configures the SPI interface
*/
public void settings(int maxSpeed, int dataOrder, int mode) {
this.maxSpeed = maxSpeed;
this.dataOrder = dataOrder;
this.mode = mode;
}
/**
* Transfers data over the SPI bus<br/>
* <br/>
* With SPI, data is simultaneously being exchanged between the master device
* and the slave device. For every byte that is being sent out, there's also one
* byte being read in.
*
* @param out bytes to send
* @return bytes read in (array is the same length as out)
* @webref SPI
* @webBrief Transfers data over the SPI bus
*/
public byte[] transfer(byte[] out) {
if (NativeInterface.isSimulated()) {
return new byte[out.length];
}
// track the current setting per device across multiple instances
String curSettings = maxSpeed + "-" + dataOrder + "-" + mode;
if (!curSettings.equals(settings.get(dev))) {
int ret = NativeInterface.setSpiSettings(handle, maxSpeed, dataOrder, mode);
if (ret < 0) {
System.err.println(NativeInterface.getError(handle));
throw new RuntimeException("Error updating device configuration");
}
settings.put(dev, curSettings);
}
byte[] in = new byte[out.length];
int transferred = NativeInterface.transferSpi(handle, out, in);
if (transferred < 0) {
throw new RuntimeException(NativeInterface.getError(transferred));
} else if (transferred < out.length) {
throw new RuntimeException("Fewer bytes transferred than requested: " + transferred);
}
return in;
}
/**
* Transfers data over the SPI bus
* @param out string to send
* @return bytes read in (array is the same length as out)
*/
public byte[] transfer(String out) {
return transfer(out.getBytes());
}
/**
* Transfers data over the SPI bus
* @param out single byte to send, e.g. numeric literal (0 to 255, or -128 to 127)
* @return bytes read in (array is the same length as out)
*/
public byte[] transfer(int out) {
if (out < -128 || 255 < out) {
System.err.println("The transfer function can only operate on a single byte at a time. Call it with a value from 0 to 255, or -128 to 127.");
throw new RuntimeException("Argument does not fit into a single byte");
}
byte[] tmp = new byte[1];
tmp[0] = (byte)out;
return transfer(tmp);
}
/**
* Transfers data over the SPI bus
* @param out single byte to send
* @return bytes read in (array is the same length as out)
*/
public byte[] transfer(byte out) {
// cast to (unsigned) int
return transfer(out & 0xff);
}
}