001package com.pi4j.wiringpi; 002 003/* 004 * #%L 005 * ********************************************************************** 006 * ORGANIZATION : Pi4J 007 * PROJECT : Pi4J :: Java Library (Core) 008 * FILENAME : Gertboard.java 009 * 010 * This file is part of the Pi4J project. More information about 011 * this project can be found here: https://www.pi4j.com/ 012 * ********************************************************************** 013 * %% 014 * Copyright (C) 2012 - 2019 Pi4J 015 * %% 016 * This program is free software: you can redistribute it and/or modify 017 * it under the terms of the GNU Lesser General Public License as 018 * published by the Free Software Foundation, either version 3 of the 019 * License, or (at your option) any later version. 020 * 021 * This program is distributed in the hope that it will be useful, 022 * but WITHOUT ANY WARRANTY; without even the implied warranty of 023 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 024 * GNU General Lesser Public License for more details. 025 * 026 * You should have received a copy of the GNU General Lesser Public 027 * License along with this program. If not, see 028 * <http://www.gnu.org/licenses/lgpl-3.0.html>. 029 * #L% 030 */ 031 032 033import com.pi4j.util.NativeLibraryLoader; 034 035/** 036 * <p> 037 * The Gertboard has an on-board Digital to Analog (DAC) converter and an Analog to Digital (ADC) 038 * converters. These are connected via the SPI bus back to the Raspberry Pi host. 039 * </p> 040 * 041 * <p> 042 * Each of the DAC and ADC chips has 2 channels. 043 * </p> 044 * 045 * <p> 046 * The DAC has a resolution of 8 bits and produces an output voltage between 0 and 2.047 volts, the 047 * ADC has a resolution of 10 bits and can take an input voltage between 0 and 3.3 volts. 048 * </p> 049 * 050 * <p> 051 * Part of the wiringPi library includes code to setup and drive these chips in an easy to use 052 * manner. 053 * </p> 054 * 055 * <p> 056 * To use in a program, first you need to make sure that the 5 SPI jumpers are present on the 057 * Gertboard (there are 7 in total, 5 for the SPI, 2 to connect the serial to the ATmega), the 058 * photo below shows all 7 jumpers in-place. 059 * </p> 060 * 061 * <p> 062 * Before using the Pi4J library, you need to ensure that the Java VM in configured with access to 063 * the following system libraries: 064 * <ul> 065 * <li>pi4j</li> 066 * <li>wiringPi</li> 067 * </ul> 068 * <blockquote> This library depends on the wiringPi native system library.</br> (developed by 069 * Gordon Henderson @ <a href="http://wiringpi.com/">http://wiringpi.com/</a>) 070 * </blockquote> 071 * </p> 072 * 073 * @see <a href="https://www.pi4j.com/">https://www.pi4j.com/</a> 074 * @see <a 075 * href="http://wiringpi.com/dev-lib/gertboard-analog/">http://wiringpi.com/dev-lib/gertboard-analog/</a> 076 * @author Robert Savage (<a 077 * href="http://www.savagehomeautomation.com">http://www.savagehomeautomation.com</a>) 078 */ 079public class Gertboard { 080 081 public static final int SPI_ADC_SPEED = 1000000; 082 public static final int SPI_DAC_SPEED = 1000000; 083 public static final int SPI_A2D = 0; 084 public static final int SPI_D2A = 1; 085 086 // private constructor 087 private Gertboard() { 088 // forbid object construction 089 } 090 091 static { 092 // Load the platform library 093 NativeLibraryLoader.load("libpi4j.so"); 094 } 095 096 /** 097 * <p> This outputs the supplied value (0-255) to the given channel (0 or 1). The output voltage is: 098 * 099 * <pre> 100 * vOut = value / 255 * 2.047 101 * </pre> 102 * 103 * or to find the value for a given voltage: 104 * 105 * <pre> 106 * value = vOut / 2.047 * 255 107 * </pre> 108 * </p> 109 * @see <a 110 * href="http://wiringpi.com/dev-lib/gertboard-analog/">http://wiringpi.com/dev-lib/gertboard-analog/</a> 111 * @param chan Analog channel to write to (0 or 1). 112 * @param value The output value (0-255) supplied to the given channel (0 or 1). 113 */ 114 public static native void gertboardAnalogWrite(int chan, int value); 115 116 /** 117 * <p> This returns a value from 0 to 1023 representing the value on the supplied channel (0 or 1). 118 * To convert this to a voltage, use the following formula: 119 * 120 * <pre> 121 * vIn = value * 3.3 / 1023 122 * </pre> 123 * </p> 124 * 125 * @see <a 126 * href="http://wiringpi.com/dev-lib/gertboard-analog/">http://wiringpi.com/dev-lib/gertboard-analog/</a> 127 * @param chan Analog channel to read from (0 or 1). 128 * @return This returns a value from 0 to 1023 representing the value on the supplied channel (0 129 * or 1). 130 */ 131 public static native int gertboardAnalogRead(int chan); 132 133 /** 134 * <p> This must be called to initialize the SPI bus to communicate with the Gertboards ADC and DAC 135 * chips. If the return value is < 0 then an error occurred and errno will be set appropriately. 136 * </p> 137 * 138 * @see <a 139 * href="http://wiringpi.com/dev-lib/gertboard-analog/">http://wiringpi.com/dev-lib/gertboard-analog/</a> 140 * @return If the return value is < 0 then an error occurred and errno will be set 141 * appropriately. If the return value is '0' or greater than the call was successful. 142 */ 143 public static native int gertboardSPISetup(); 144 145 146 147 /** 148 * <p> 149 * This setup routine allocates 2 pins and overlays the analog to digital input pins with the digital to analog 150 * output pins. So reading channel pinBase + 0 reads the first analog input channel (pin DA0 on the Gertboard), 151 * and writing pinBase + 0 outputs to the first analog output channel. (Pin AD0). 152 * </p> 153 * 154 * @see <a 155 * href="http://wiringpi.com/dev-lib/gertboard-analog/">http://wiringpi.com/dev-lib/gertboard-analog/</a> 156 * @param pinBase pinBase is the base pin that you want the analog ports to appear as 157 * @return If the return value is < 0 then an error occurred and errno will be set 158 * appropriately. If the return value is '0' or greater than the call was successful. 159 */ 160 public static native int gertboardAnalogSetup(int pinBase); 161}