001package com.pi4j.wiringpi; 002 003/* 004 * #%L 005 * ********************************************************************** 006 * ORGANIZATION : Pi4J 007 * PROJECT : Pi4J :: Java Library (Core) 008 * FILENAME : Spi.java 009 * 010 * This file is part of the Pi4J project. More information about 011 * this project can be found here: http://www.pi4j.com/ 012 * ********************************************************************** 013 * %% 014 * Copyright (C) 2012 - 2013 Pi4J 015 * %% 016 * Licensed under the Apache License, Version 2.0 (the "License"); 017 * you may not use this file except in compliance with the License. 018 * You may obtain a copy of the License at 019 * 020 * http://www.apache.org/licenses/LICENSE-2.0 021 * 022 * Unless required by applicable law or agreed to in writing, software 023 * distributed under the License is distributed on an "AS IS" BASIS, 024 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 025 * See the License for the specific language governing permissions and 026 * limitations under the License. 027 * #L% 028 */ 029 030 031import com.pi4j.util.NativeLibraryLoader; 032 033/** 034 * <p> 035 * WiringPi includes a software-driven PWM handler capable of outputting a PWM signal on any of the 036 * Raspberry Pi's GPIO pins. 037 * </p> 038 * 039 * <p> 040 * There are some limitations. To maintain a low CPU usage, the minimum pulse width is 100uS. That 041 * combined with the default suggested range of 100 gives a PWM frequency of 100Hz. You can lower 042 * the range to get a higher frequency, at the expense of resolution, or increase to get more 043 * resolution, but that will lower the frequency. If you change the pulse-width in the drive code, 044 * then be aware that at delays of less than 100uS wiringPi does it in a software loop, which means 045 * that CPU usage will rise dramatically, and controlling more than one pin will be almost 046 * impossible. 047 * </p> 048 * 049 * <p> 050 * Also note that while the routines run themselves at a higher and real-time priority, Linux can 051 * still affect the accuracy of the generated signal. 052 * </p> 053 * 054 * <p> 055 * However, within these limitations, control of a light/LED or a motor is very achievable. 056 * </p> 057 * 058 * <p> 059 * <b>You must initialize wiringPi with one of wiringPiSetup() or wiringPiSetupGpio() functions 060 * beforehand. wiringPiSetupSys() is not fast enough, so you must run your programs with sudo.</b> 061 * </p> 062 * 063 * <p> 064 * Before using the Pi4J library, you need to ensure that the Java VM in configured with access to 065 * the following system libraries: 066 * <ul> 067 * <li>pi4j</li> 068 * <li>wiringPi</li> 069 * <li>pthread</li> 070 * </ul> 071 * <blockquote> This library depends on the wiringPi native system library.</br> (developed by 072 * Gordon Henderson @ <a href="https://projects.drogon.net/">https://projects.drogon.net/</a>) 073 * </blockquote> 074 * </p> 075 * 076 * @see <a href="http://www.pi4j.com/">http://www.pi4j.com/</a> 077 * @author Robert Savage (<a 078 * href="http://www.savagehomeautomation.com">http://www.savagehomeautomation.com</a>) 079 */ 080public class Spi { 081 082 public static int CHANNEL_0 = 0; 083 public static int CHANNEL_1 = 1; 084 085 // private constructor 086 private Spi() { 087 // forbid object construction 088 } 089 090 static { 091 // Load the platform library 092 NativeLibraryLoader.load("pi4j", "libpi4j.so"); 093 } 094 095 /** 096 * <p>wiringPiSPIGetFd:</p> 097 * 098 * <p> 099 * Return the file-descriptor for the given channel 100 * </p> 101 * 102 * @param channel SPI channel 103 * @return file-descriptor for the given channel 104 */ 105 public static native int wiringPiSPIGetFd(int channel); 106 107 /** 108 * <p>wiringPiSPIDataRW:</p> 109 * 110 * <p> 111 * Write and Read a block of data over the SPI bus. Note the data is being read into the 112 * transmit buffer, so will overwrite it! This is also a full-duplex operation. 113 * </p> 114 * 115 * <p> 116 * (ATTENTION: the 'data' argument can only be a maximum of 1024 characters.) 117 * </p> 118 * 119 * @param channel SPI channel</p> 120 * @param data 121 * @param len 122 * @return return -1 on error 123 */ 124 public static native int wiringPiSPIDataRW(int channel, String data, int len); 125 126 /** 127 * <p>wiringPiSPIDataRW:</p> 128 * 129 * <p> 130 * Write and Read a block of data over the SPI bus. Note the data is being read into the 131 * transmit buffer, so will overwrite it! This is also a full-duplex operation. 132 * </p> 133 * 134 * <p> 135 * (ATTENTION: the 'data' argument can only be a maximum of 1024 characters.) 136 * </p> 137 * 138 * @param channel SPI channel</p> 139 * @param data 140 * @param len 141 * @return return -1 on error 142 */ 143 public static native int wiringPiSPIDataRW(int channel, byte[] data, int len); 144 145 /** 146 * <p>wiringPiSPISetup:</p> 147 * 148 * <p> 149 * Open the SPI device, and set it up, etc.</b> 150 * 151 * @param channel SPI channel 152 * @param speed SPI speed 153 * @return return -1 on error 154 */ 155 public static native int wiringPiSPISetup(int channel, int speed); 156}