Merge pull request #84 from aj-ptw/dropped-packet-alert

Add dropped packet detection

Author: AJ Keller

README.md

@@ -1040,13 +1040,17 @@ ourBoard.write('o');
 
 Emitted when the serial connection to the board is closed.
 
+### <a name="event-close"></a> .on('droppedPacket', callback)
+
+Emitted when a packet (or packets) are dropped. Returns an array.
+
 ### <a name="event-error"></a> .on('error', callback)
 
 Emitted when there is an on the serial port.
 
 ### <a name="event-impedance-array"></a> .on('impedanceArray', callback)
 
-Emitted when there is a new impedanceArray available.
+Emitted when there is a new impedanceArray available. Returns an array.
 
 ### <a name="event-query"></a> .on('query', callback)
 

changelog.md

@@ -1,3 +1,9 @@
+# 1.3.0
+
+### New Features
+
+* Add dropped packet detection, new event `droppedPacket` can be added to get an array of dropped packet numbers in the case of the dropped packet event.
+
 # 1.2.3
 
 ### Enhancements

openBCIBoard.js

@@ -185,9 +185,10 @@ function OpenBCIFactory() {
         this.curParsingMode = k.OBCIParsingReset;
         this.commandsToWrite = 0;
         this.impedanceArray = openBCISample.impedanceArray(k.numberOfChannelsForBoardType(this.options.boardType));
-        this.writeOutDelay = k.OBCIWriteIntervalDelayMSShort;
+        this.previousSampleNumber = -1;
         this.sampleCount = 0;
         this.timeOfPacketArrival = 0;
+        this.writeOutDelay = k.OBCIWriteIntervalDelayMSShort;
         // Strings
 
         // NTP
@@ -1735,6 +1736,11 @@ function OpenBCIFactory() {
     OpenBCIBoard.prototype._processQualifiedPacket = function(rawDataPacketBuffer) {
         if (!rawDataPacketBuffer) return;
         if (rawDataPacketBuffer.byteLength !== k.OBCIPacketSize) return;
+        var missedPacketArray = openBCISample.droppedPacketCheck(this.previousSampleNumber, rawDataPacketBuffer[k.OBCIPacketPositionSampleNumber]);
+        if (missedPacketArray) {
+            this.emit('droppedPacket', missedPacketArray);
+        }
+        this.previousSampleNumber = rawDataPacketBuffer[k.OBCIPacketPositionSampleNumber];
         var packetType = openBCISample.getRawPacketType(rawDataPacketBuffer[k.OBCIPacketPositionStopByte]);
         switch (packetType) {
             case k.OBCIStreamPacketStandardAccel:

openBCIConstants.js

@@ -199,6 +199,9 @@ const OBCISimulatorLineNoiseNone = 'None';
 const OBCISampleRate125 = 125;
 const OBCISampleRate250 = 250;
 
+/** Max sample number */
+const OBCISampleNumberMax = 255;
+
 /** Packet Size */
 const OBCIPacketSize = 33;
 
@@ -729,6 +732,8 @@ module.exports = {
     /** Possible Sample Rates */
     OBCISampleRate125,
     OBCISampleRate250,
+    /** Max sample number */
+    OBCISampleNumberMax,
     /** Packet Size */
     OBCIPacketSize,
     /** Notable Bytes */

openBCISample.js

@@ -522,7 +522,42 @@ var sampleModule = {
     isTimeSyncSetConfirmationInBuffer,
     makeTailByteFromPacketType,
     isStopByte,
-    newSyncObject
+    newSyncObject,
+    /**
+     * @description Checks to make sure the previous sample number is one less
+     *  then the new sample number. Takes into account sample numbers wrapping
+     *  around at 255.
+     * @param `previousSampleNumber` {Number} - An integer number of the previous
+     *  sample number.
+     * @param `newSampleNumber` {Number} - An integer number of the new sample
+     *  number.
+     * @returns {Array} - Returns null if there is no dropped packets, otherwise,
+     *  or on a missed packet, an array of their packet numbers is returned.
+     */
+    droppedPacketCheck: (previousSampleNumber, newSampleNumber) => {
+        if (previousSampleNumber === k.OBCISampleNumberMax && newSampleNumber === 0) {
+            return null;
+        }
+
+        if (newSampleNumber - previousSampleNumber === 1) {
+            return null;
+        }
+
+        var missedPacketArray = [];
+
+        if (previousSampleNumber > newSampleNumber) {
+          var numMised = k.OBCISampleNumberMax - previousSampleNumber;
+          for (var i = 0; i < numMised; i++) {
+              missedPacketArray.push(previousSampleNumber + i + 1);
+          }
+          previousSampleNumber = -1;
+        }
+
+        for (var i = 1; i < (newSampleNumber - previousSampleNumber); i++) {
+            missedPacketArray.push(previousSampleNumber + i);
+        }
+        return missedPacketArray;
+    }
 };
 
 module.exports = sampleModule;

package.json

@@ -1,6 +1,6 @@
 {
   "name": "openbci",
-  "version": "1.2.3",
+  "version": "1.3.0",
   "description": "The official Node.js SDK for the OpenBCI Biosensor Board.",
   "main": "openBCIBoard",
   "scripts": {

test/OpenBCIConstants-test.js

@@ -765,6 +765,11 @@ describe('OpenBCIConstants', function() {
             assert.equal(250, k.OBCISampleRate250);
         });
     });
+    describe('Max sample number',function() {
+        it('should be 255',function () {
+            assert.equal(255, k.OBCISampleNumberMax);
+        });
+    });
     describe("Radio Channel Limits", function() {
         it("should get the right channel number max",function () {
             expect(k.OBCIRadioChannelMax).to.be.equal(25);

test/OpenBCISample-test.js

@@ -5,9 +5,9 @@ var assert = require('assert');
 var openBCISample = require('../openBCISample');
 var sinon = require('sinon');
 var chai = require('chai'),
-    expect = chai.expect,
     should = chai.should(),
-    expect = chai.expect;
+    expect = chai.expect,
+    assert = chai.assert;
 
 var chaiAsPromised = require("chai-as-promised");
 var sinonChai = require("sinon-chai");
@@ -1373,7 +1373,41 @@ describe('openBCISample',function() {
         it("should have property boardTime",function() {
             expect(syncObj).to.have.property("boardTime",0);
         });
-    })
+    });
+    describe('#droppedPacketCheck',function() {
+        it("should return an array of missed packet numbers",function() {
+            previous = 0;
+            current = previous + 2;
+            assert.sameMembers(openBCISample.droppedPacketCheck(previous, current), [1], "dropped one packet");
+
+            previous = 0;
+            current = previous + 4;
+            assert.sameMembers(openBCISample.droppedPacketCheck(previous, current), [1,2,3], "dropped three packets");
+
+            previous = 255;
+            current = 2;
+            assert.sameMembers(openBCISample.droppedPacketCheck(previous, current), [0,1], "dropped two packets on wrap edge!");
+
+            previous = 254;
+            current = 2;
+            assert.sameMembers(openBCISample.droppedPacketCheck(previous, current), [255,0,1], "dropped three packets on wrap!");
+
+            previous = 250;
+            current = 1;
+            assert.sameMembers(openBCISample.droppedPacketCheck(previous, current), [251,252,253,254,255,0], "dropped a bunch of packets on wrap!");
+
+        });
+        it("should roll over when 255 was previous and current is 0", function() {
+            previous = 255;
+            current = 0;
+            expect(openBCISample.droppedPacketCheck(previous, current)).to.be.null;
+        });
+        it("should return null when previous is one less then new sample number", function() {
+            previous = 0;
+            current = previous + 1;
+            expect(openBCISample.droppedPacketCheck(previous, current)).to.be.null;
+        });
+    });
 });
 
 

test/openBCIBoard-test.js

@@ -1010,6 +1010,39 @@ describe('openbci-sdk',function() {
             funcSpyTimeSyncedAccel.should.not.have.been.called;
             funcSpyTimeSyncedRawAux.should.not.have.been.called;
         });
+        it("should emit a dropped packet on dropped packet",function(done) {
+          // Set to default state
+          ourBoard.previousSampleNumber = -1;
+          var sampleNumber0 = openBCISample.samplePacket(0);
+          ourBoard.once('droppedPacket',() => {
+              done();
+          });
+          var sampleNumber2 = openBCISample.samplePacket(2);
+          // Call the function under test
+          ourBoard._processDataBuffer(sampleNumber0);
+          ourBoard._processDataBuffer(sampleNumber2);
+        });
+        it("should emit a dropped packet on dropped packet with edge",function(done) {
+          // Set to default state
+          var count = 0;
+          ourBoard.previousSampleNumber = 253;
+          var buf1 = openBCISample.samplePacket(254);
+          var countFunc = arr => {
+              count++;
+          };
+          ourBoard.on('droppedPacket', countFunc);
+          var buf2 = openBCISample.samplePacket(0);
+          var buf3 = openBCISample.samplePacket(1);
+          // Call the function under test
+          ourBoard._processDataBuffer(buf1);
+          ourBoard._processDataBuffer(buf2);
+          ourBoard._processDataBuffer(buf3);
+          setTimeout(() => {
+            ourBoard.removeListener('droppedPacket', countFunc);
+            expect(count).to.equal(1);
+            done();
+          }, 10)
+        });
     });
 
     describe("#_processPacketTimeSyncSet", function() {