001// Copyright (c) FIRST and other WPILib contributors. 002// Open Source Software; you can modify and/or share it under the terms of 003// the WPILib BSD license file in the root directory of this project. 004 005package edu.wpi.first.wpilibj; 006 007import static java.util.Objects.requireNonNull; 008 009import edu.wpi.first.hal.FRCNetComm.tResourceType; 010import edu.wpi.first.hal.HAL; 011import edu.wpi.first.hal.SimBoolean; 012import edu.wpi.first.hal.SimDevice; 013import edu.wpi.first.hal.SimDevice.Direction; 014import edu.wpi.first.hal.SimDouble; 015import edu.wpi.first.util.sendable.Sendable; 016import edu.wpi.first.util.sendable.SendableBuilder; 017import edu.wpi.first.util.sendable.SendableRegistry; 018import java.util.ArrayList; 019import java.util.List; 020 021/** 022 * Ultrasonic rangefinder class. The Ultrasonic rangefinder measures absolute distance based on the 023 * round-trip time of a ping generated by the controller. These sensors use two transducers, a 024 * speaker and a microphone both tuned to the ultrasonic range. A common ultrasonic sensor, the 025 * Daventech SRF04 requires a short pulse to be generated on a digital channel. This causes the 026 * chirp to be emitted. A second line becomes high as the ping is transmitted and goes low when the 027 * echo is received. The time that the line is high determines the round trip distance (time of 028 * flight). 029 */ 030public class Ultrasonic implements Sendable, AutoCloseable { 031 // Time (sec) for the ping trigger pulse. 032 private static final double kPingTime = 10 * 1e-6; 033 private static final double kSpeedOfSoundInchesPerSec = 1130.0 * 12.0; 034 // ultrasonic sensor list 035 private static final List<Ultrasonic> m_sensors = new ArrayList<>(); 036 // automatic round robin mode 037 private static volatile boolean m_automaticEnabled; 038 private DigitalInput m_echoChannel; 039 private DigitalOutput m_pingChannel; 040 private final boolean m_allocatedChannels; 041 private boolean m_enabled; 042 private Counter m_counter; 043 // task doing the round-robin automatic sensing 044 private static Thread m_task; 045 private static int m_instances; 046 047 private SimDevice m_simDevice; 048 private SimBoolean m_simRangeValid; 049 private SimDouble m_simRange; 050 051 /** 052 * Background task that goes through the list of ultrasonic sensors and pings each one in turn. 053 * The counter is configured to read the timing of the returned echo pulse. 054 * 055 * <p><b>DANGER WILL ROBINSON, DANGER WILL ROBINSON:</b> This code runs as a task and assumes that 056 * none of the ultrasonic sensors will change while it's running. If one does, then this will 057 * certainly break. Make sure to disable automatic mode before changing anything with the 058 * sensors!! 059 */ 060 private static class UltrasonicChecker extends Thread { 061 @Override 062 public synchronized void run() { 063 while (m_automaticEnabled) { 064 for (Ultrasonic sensor : m_sensors) { 065 if (!m_automaticEnabled) { 066 break; 067 } 068 069 if (sensor.isEnabled()) { 070 sensor.m_pingChannel.pulse(kPingTime); // do the ping 071 } 072 073 Timer.delay(0.1); // wait for ping to return 074 } 075 } 076 } 077 } 078 079 /** 080 * Initialize the Ultrasonic Sensor. This is the common code that initializes the ultrasonic 081 * sensor given that there are two digital I/O channels allocated. If the system was running in 082 * automatic mode (round robin) when the new sensor is added, it is stopped, the sensor is added, 083 * then automatic mode is restored. 084 */ 085 private synchronized void initialize() { 086 m_simDevice = SimDevice.create("Ultrasonic", m_echoChannel.getChannel()); 087 if (m_simDevice != null) { 088 m_simRangeValid = m_simDevice.createBoolean("Range Valid", Direction.kInput, true); 089 m_simRange = m_simDevice.createDouble("Range (in)", Direction.kInput, 0.0); 090 m_pingChannel.setSimDevice(m_simDevice); 091 m_echoChannel.setSimDevice(m_simDevice); 092 } 093 if (m_task == null) { 094 m_task = new UltrasonicChecker(); 095 } 096 final boolean originalMode = m_automaticEnabled; 097 setAutomaticMode(false); // kill task when adding a new sensor 098 m_sensors.add(this); 099 100 m_counter = new Counter(m_echoChannel); // set up counter for this 101 SendableRegistry.addChild(this, m_counter); 102 // sensor 103 m_counter.setMaxPeriod(1.0); 104 m_counter.setSemiPeriodMode(true); 105 m_counter.reset(); 106 m_enabled = true; // make it available for round robin scheduling 107 setAutomaticMode(originalMode); 108 109 m_instances++; 110 HAL.report(tResourceType.kResourceType_Ultrasonic, m_instances); 111 SendableRegistry.addLW(this, "Ultrasonic", m_echoChannel.getChannel()); 112 } 113 114 public int getEchoChannel() { 115 return m_echoChannel.getChannel(); 116 } 117 118 /** 119 * Create an instance of the Ultrasonic Sensor. This is designed to supchannel the Daventech SRF04 120 * and Vex ultrasonic sensors. 121 * 122 * @param pingChannel The digital output channel that sends the pulse to initiate the sensor 123 * sending the ping. 124 * @param echoChannel The digital input channel that receives the echo. The length of time that 125 * the echo is high represents the round trip time of the ping, and the distance. 126 */ 127 public Ultrasonic(final int pingChannel, final int echoChannel) { 128 m_pingChannel = new DigitalOutput(pingChannel); 129 m_echoChannel = new DigitalInput(echoChannel); 130 SendableRegistry.addChild(this, m_pingChannel); 131 SendableRegistry.addChild(this, m_echoChannel); 132 m_allocatedChannels = true; 133 initialize(); 134 } 135 136 /** 137 * Create an instance of an Ultrasonic Sensor from a DigitalInput for the echo channel and a 138 * DigitalOutput for the ping channel. 139 * 140 * @param pingChannel The digital output object that starts the sensor doing a ping. Requires a 141 * 10uS pulse to start. 142 * @param echoChannel The digital input object that times the return pulse to determine the range. 143 */ 144 public Ultrasonic(DigitalOutput pingChannel, DigitalInput echoChannel) { 145 requireNonNull(pingChannel, "Provided ping channel was null"); 146 requireNonNull(echoChannel, "Provided echo channel was null"); 147 148 m_allocatedChannels = false; 149 m_pingChannel = pingChannel; 150 m_echoChannel = echoChannel; 151 initialize(); 152 } 153 154 /** 155 * Destructor for the ultrasonic sensor. Delete the instance of the ultrasonic sensor by freeing 156 * the allocated digital channels. If the system was in automatic mode (round robin), then it is 157 * stopped, then started again after this sensor is removed (provided this wasn't the last 158 * sensor). 159 */ 160 @Override 161 public synchronized void close() { 162 SendableRegistry.remove(this); 163 final boolean wasAutomaticMode = m_automaticEnabled; 164 setAutomaticMode(false); 165 if (m_allocatedChannels) { 166 if (m_pingChannel != null) { 167 m_pingChannel.close(); 168 } 169 if (m_echoChannel != null) { 170 m_echoChannel.close(); 171 } 172 } 173 174 if (m_counter != null) { 175 m_counter.close(); 176 m_counter = null; 177 } 178 179 m_pingChannel = null; 180 m_echoChannel = null; 181 synchronized (m_sensors) { 182 m_sensors.remove(this); 183 } 184 if (!m_sensors.isEmpty() && wasAutomaticMode) { 185 setAutomaticMode(true); 186 } 187 188 if (m_simDevice != null) { 189 m_simDevice.close(); 190 m_simDevice = null; 191 } 192 } 193 194 /** 195 * Turn Automatic mode on/off for all sensors. 196 * 197 * <p>When in Automatic mode, all sensors will fire in round robin, waiting a set time between 198 * each sensor. 199 * 200 * @param enabling Set to true if round robin scheduling should start for all the ultrasonic 201 * sensors. This scheduling method assures that the sensors are non-interfering because no two 202 * sensors fire at the same time. If another scheduling algorithm is preferred, it can be 203 * implemented by pinging the sensors manually and waiting for the results to come back. 204 */ 205 public static void setAutomaticMode(boolean enabling) { 206 if (enabling == m_automaticEnabled) { 207 return; // ignore the case of no change 208 } 209 m_automaticEnabled = enabling; 210 211 if (enabling) { 212 /* Clear all the counters so no data is valid. No synchronization is 213 * needed because the background task is stopped. 214 */ 215 for (Ultrasonic u : m_sensors) { 216 u.m_counter.reset(); 217 } 218 219 // Start round robin task 220 m_task.start(); 221 } else { 222 // Wait for background task to stop running 223 try { 224 m_task.join(); 225 } catch (InterruptedException ex) { 226 Thread.currentThread().interrupt(); 227 ex.printStackTrace(); 228 } 229 230 /* Clear all the counters (data now invalid) since automatic mode is 231 * disabled. No synchronization is needed because the background task is 232 * stopped. 233 */ 234 for (Ultrasonic u : m_sensors) { 235 u.m_counter.reset(); 236 } 237 } 238 } 239 240 /** 241 * Single ping to ultrasonic sensor. Send out a single ping to the ultrasonic sensor. This only 242 * works if automatic (round robin) mode is disabled. A single ping is sent out, and the counter 243 * should count the semi-period when it comes in. The counter is reset to make the current value 244 * invalid. 245 */ 246 public void ping() { 247 setAutomaticMode(false); // turn off automatic round robin if pinging 248 // single sensor 249 m_counter.reset(); // reset the counter to zero (invalid data now) 250 // do the ping to start getting a single range 251 m_pingChannel.pulse(kPingTime); 252 } 253 254 /** 255 * Check if there is a valid range measurement. The ranges are accumulated in a counter that will 256 * increment on each edge of the echo (return) signal. If the count is not at least 2, then the 257 * range has not yet been measured, and is invalid. 258 * 259 * @return true if the range is valid 260 */ 261 public boolean isRangeValid() { 262 if (m_simRangeValid != null) { 263 return m_simRangeValid.get(); 264 } 265 return m_counter.get() > 1; 266 } 267 268 /** 269 * Get the range in inches from the ultrasonic sensor. If there is no valid value yet, i.e. at 270 * least one measurement hasn't completed, then return 0. 271 * 272 * @return double Range in inches of the target returned from the ultrasonic sensor. 273 */ 274 public double getRangeInches() { 275 if (isRangeValid()) { 276 if (m_simRange != null) { 277 return m_simRange.get(); 278 } 279 return m_counter.getPeriod() * kSpeedOfSoundInchesPerSec / 2.0; 280 } else { 281 return 0; 282 } 283 } 284 285 /** 286 * Get the range in millimeters from the ultrasonic sensor. If there is no valid value yet, i.e. 287 * at least one measurement hasn't completed, then return 0. 288 * 289 * @return double Range in millimeters of the target returned by the ultrasonic sensor. 290 */ 291 public double getRangeMM() { 292 return getRangeInches() * 25.4; 293 } 294 295 /** 296 * Is the ultrasonic enabled. 297 * 298 * @return true if the ultrasonic is enabled 299 */ 300 public boolean isEnabled() { 301 return m_enabled; 302 } 303 304 /** 305 * Set if the ultrasonic is enabled. 306 * 307 * @param enable set to true to enable the ultrasonic 308 */ 309 public void setEnabled(boolean enable) { 310 m_enabled = enable; 311 } 312 313 @Override 314 public void initSendable(SendableBuilder builder) { 315 builder.setSmartDashboardType("Ultrasonic"); 316 builder.addDoubleProperty("Value", this::getRangeInches, null); 317 } 318}