Argent OpenTracker User manual

OpenTracker
User’s Manual
PCB Revision 4





1. Introduction

TheOpenTrackerisasimple,low‐costamateurradiodataencodercapableofgenerating1200
or300baudAX.25packetsusingbothAPRS™andOpenTRACprotocols,aswellasPSK31text
beacons.ItcanbeconnectedtoaGPSreceivertoreportposition,courseandspeed,time,and
altitude,andwillalsoreporttelemetryfromitsonboardtemperatureandvoltagesensors.With
itsexpansionconnectorandeaseofreprogramming,thedevicecanbeadaptedtoawide
varietyoftasks.

Changes

PCBRevision4includessignificantchangesfromprevioushardwarerevisions.Whilethe
firmwarefeaturesandconfigurationoptionsremainthesame,thepinheaderconfigurationand
powerspecificationshavechanged.Revision4incorporatesalargervoltageregulatorcapable
ofsupplyingenoughcurrenttopowermanypopular5‐voltGPSreceiverswithoutrequiringa
heatsink.

Acknowledgements

TheOpenTrackerisfarfrombeingthefirstdeviceofitstype,andowesmuchtothosethatcame
before–inparticular,JohnHansen’sGPS‐EfirmwareanditsTAPRPIC‐Ehardware,Steve
Bragg’sHamHUD,andByonGarrabrant’sverysuccessfulTinyTrakseries.Lessonslearned
fromallofthesedeviceshavecontributedtothedesignoftheOpenTracker.TheOpenTrackeris
verysimilarinphysicallayouttotheTinyTrak3(inits‘trimmed’version),andidenticalin
connectorconfiguration,allowingenclosuresandcablestobeusedinterchangeably.Despite
theirsimilarities,though,thetwodeviceshaveverydifferentprocessorarchitectures,different
digital‐to‐analogconversionsystems,andentirelyunrelatedfirmware.TheSmartBeaconing™
algorithmusedbytheOpenTrackerwasoriginallydevelopedbyTonyArnerich,KD7TA,and
SteveBragg,KA9MVA.APRS™isatrademarkofBobBruninga,WB4APR.BrianRiley,N1BQ,
andKeriMorgret,N6TME,contributedtothismanual.
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Table of Contents
1.Introduction ............................................................................................................................................2
2.OpenTrackerAssemblyNotes .............................................................................................................4
3.ConnectorPinAssignments .................................................................................................................6
a.General ................................................................................................................................................7
b.ReceiveAdjustment ..........................................................................................................................7
c.TransmitAdjustment ........................................................................................................................7
d.LEDBlinkCodes ...............................................................................................................................8
e.ConfigurationProgram.....................................................................................................................8
f.Mainconfigurationwindow.............................................................................................................9
5.InstallingNewFirmware....................................................................................................................14
6.WeatherStationOperation .................................................................................................................15
7.TelemetryOperation............................................................................................................................ 16
8.OpenTrackerCircuitDetails...............................................................................................................17
TheoryofOperation............................................................................................................................ 18
AppendixA–TestProcedures ..............................................................................................................20
a.Measurements ..................................................................................................................................20
AppendixB–APRSsymboltables........................................................................................................21
AppendixC–CommonModifications................................................................................................. 23
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2. OpenTracker Assembly Notes

Table1–PartsList

Part Description Notes
 
U1MC908KX8MCUwithsocketReferencenotchfacesleft
U278M05VoltageRegulatorInstallfirst
U3LM335ZAligntosilkscreenoutline
R1,R710KresistorBrown‐Black‐Orange
R2220KresistorRed‐Red‐Yellow
R32.2KresistorRed‐Red‐Red
R41KresistorBrown‐Black‐Red
R53KresistorOrange‐Black‐Red
R66.8K*resistorBlue‐Gray‐Red
R8,R910KpotentiometerAlignpinstoholes
R1010MresistorBrown‐Black‐Blue
R1120KresistorRed‐Black‐Orange
JP110‐pinheaderSinglerow.100pins
C10.33uFcapacitorYellowwith“334”marking
C2‐C40.1uFcapacitorYellowwith“104”marking
C6,C718pFcapacitor“180”or“180j”marking
Q3,Q42N7000transistorAligntosilkscreenoutline
D1‐D21N914or1N4148diodeBlackbanddenotescathode
LEDRedLEDShortleadfacestowardR4
X1DB9Connector‐femaleLeftedgeofboard
X2DB9Connector‐maleRightedgeofboard
Y129.4912MHzcrystalBenddowntoPCBbeforesoldering
*A6.2Kresistor(Blue‐Red‐Red)maybesubstitutedforR6

TheOpenTrackerkitrequiresbasictointermediatelevelsolderingskills.Youwillneedalow‐
wattagesolderingiron,wirecutters,andsolder.Rosincoresolderisrecommended–neveruse
acidcoresolderforelectronics.

Reviewthepartslistandidentifythecomponentsyoureceived.Ifanyaremissingordamaged,
contact[email protected]forreplacements.Don’tworryifyourkitincludesextraresistorsor
otherpartsnotlistedabove–theseareprovidedformodificationsandalternateversionsofthe
kit.

U2isasurfacemountdeviceandshouldbeinstalledfirstforeaseofsoldering.Applyasmall
dropofsoldertoonepadandkeepitmeltedwhileyoualignthepart.Soldertheotherlegand
themetaltabatthetop,makingsurethatthesolderformsagoodjunctionbetweenthetaband
thecircuitboardforproperheattransfer.

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TheDB9connectorsshouldbesolderednext.Notethatthemaleconnectoris
installedontherightside,andthefemaleconnectorisinstalledontheleft.
Therestofthepartsmaybeinstalledinanyorder.

The16‐pinDIPsocketforthemicrocontroller,U1,isoptional,but
recommendedtofacilitatereplacement.ResistorR3isusedforPTTkeying
withcertaintypesofhandheldradios.Forotherradios,particularlymobiles
andKenwoodhandhelds,thisresistormaybeomitted.Seesection4formore
information.

Paycloseattentiontocomponentpolarity.DiodesD1andD2havetheircathodeendsmarked
withablackband.Thiscorrespondstothelineatthepointedendofthesymbolshownforthese
partsonthesilkscreen.TheLEDshouldhaveitsshortleadand/orflatedgeinstalledtotheleft,
facingD1.Themicrocontroller,U1,hasareferencenotchononeedgethatshouldfaceleftas
showninthediagrambelow.

TostraightenU1’spinspriortoinsertion,placeonerowofpinsonahard,flatsurface.Holdthe
ICbytheedgesandgentlyrollituntilthepinsreachthecorrectangle.Repeatfortheother
row,andinserttheICintoitssocketgently,makingsurethateachpinisalignedwithitshole.

Installalldiodesandresistorsvertically.Oneleadshouldbebentaroundparalleltothe
component.Forresistors,thebodyofthecomponentisinstalledoverthepadindicatedwitha
circleonthesilkscreen.

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3. Connector Pin Assignments

Table2–PinHeader1(JP1)
PinDesignatorNotes
JP1PTTInputorRelayOutSeenote#1
JP2Ground
JP3JumperUsuallyusedtoswitchconfigurations
JP4IRQSeeNote#2
JP5ADC0On‐boardtemperaturesensor
JP6ADC1On‐boarddividerprovides1/3Vin
JP7ADC2ExtraADCinputor1‐wiredatabus
JP8Vin 6.7to35VDC
JP9Vext (seeNote#3)
JP10+5VoltsDCOutputofregulatorU2

Note#1–JP1canbeusedforeitherPTTinputformicencoderoperation,orasarelaycontrol
outputifpowercontrolisenabled.Whenusedasarelayoutput,thepincanprovidenomore
than15macurrent.

Note#2–JP4pulledmomentarilytogroundwillforceanimmediatetransmit.

Note#3–IfJP8andJP9arejumperedtogether,pin4onconnecterX2(SerialPort)canbeused
tosupplyrawvoltage(Vin)toanexternaldevicesuchasaGPSreceiver,ortoreceivepowervia
aspeciallywiredcableassembly.JP9andJP10maybeconnectedtoprovideregulated5volt
poweronpin4.

Table3–DB9Female(X1)–RadioPort

Table4–DB9Male(X2)–SerialPort
PinFunction
1NoConnection
2DataIn
3DataOut
4Vext
5Ground
6NoConnection
7NoConnection
8NoConnection
9NoConnection
PinFunction
1AudioOut
2COR/SquelchInput
3PTT
4NoConnection
5AudioIn
6Ground
7Powerin
8PTTInput
9NoConnection
X2iswiredasDTEtoallowconnectiontoaGPSreceiverusingastandardcable.Anullmodem
cableisrequiredforconnectiontoacomputer.

Bydefault,theOpenTrackerexpectsGPSdatatobeinNMEA‐0183formatat4800baud.
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4. OpenTracker Setup and Operation

a. General
TheOpenTrackerradioconnector,X1,isidenticaltothatusedbytheKantronicsKPC‐3andthe
ByonicsTinyTrak3.Anycablethatwasmadetointerfacearadiotoeitherofthesedevices
shouldworkwithOpenTracker.BUXCommprovidesdetailedwiringdiagramsandpre‐
assembledcablesforawidevarietyofradiosathttp://www.packetradio.com/wiring.htm.

Mosthandheldradios(withthenotableexceptionofthosemadebyKenwood)assertPTTby
groundingthemicrophoneinput.ResistorR3isusedforthispurpose.R3shouldbeomitted
whenthetrackerisusedwithmobileradiosorwithhandheldsthatdonotusethismethodof
PTTkeying.Ifthetrackerwillbeusedwithbothmobileandhandheldradios,R3canbe
installedinthecableusedtoconnectthetrackertothehandheld.

TheOpenTrackerrequires6.7to30voltsDC.IfR11andR12areinstalled,theOpenTrackercan
measureandreportitsvoltageinputlevel.However,themeasurementrangeislimitedto6.7to
15volts.

PowermaybesuppliedatthreepointsontheOpenTrackerboard.Mostoften,itissupplied
throughpin7oftheradioconnector.Itmayalsobesuppliedthroughpin8oftheexpansion
header.Inaddition,ifajumperisinstalledbetweenpins8and9oftheexpansionheader,
powermaybesuppliedthroughpin4ofthedataconnector.

b. Receive Adjustment
TheOpenTrackercannotdecodeincomingpacketdata.Instead,itwatchesforaudioenergy
(voice,data,orstatic)toavoidtransmittingoverotherstations.Thesensitivityoftheenergy
detectisdeterminedbythetrimpotlabeled‘RX’.

Adjustthesquelchonthereceiversothatitremainsclosedunderaveragechannelconditions
withnosignalspresent.TurnRXpotentiometerallthewayupsothatitremainslighted,and
thenturnitbackdownuntilitstopsblinkingunderquietchannelconditions.

c. Transmit Adjustment
The‘TX’potentiometersetstheunit’stransmitaudiolevel.Tosetthislevelproperly,use
anotherradiotolistentotheunit’stransmittedpackets.Turnthelevelupslowlyuntilthesignal
doesn’tgetanylouder,andthenturnitbackdownuntilitgetsnoticeablyquieter.Continue
turningitdownforabout1/8turnafterthatpoint.Properaudioleveliscriticaltoensuringthe
transmittedpacketscanbereceivedanddecoded.Atransmitaudiolevelsettoohighwill
causeclippinginthetransmitter,whichresultsinsignalsthataredifficulttodecode.

Theconfigurationsoftwarealsoallowsadjustmentoftheaudiooutputlevelusingaslider
control.Seethesoftwaredocumentationfordetails.
OpenTracker Manual - Version 1.05 – 6/25/06 page 7of 23

d. LED Blink Codes
ThetrackerreportsitsstatusthroughtheuseofasingleLEDasfollows:

ActionMeaning
RapidblinkingChannelisinuse
SingleflashReceivedvalidGPSfix
DoubleflashReceivedinvalidGPSfix.GPSmaynotbeready
LitsolidTransmittingorinconfigurationmode

Note‐IftheLEDisblinkingrapidlywhenthechannelisnotinuse,thereceivesensitivityis
probablysettoohigh.AdjusttheRXtrimpotuntiltheLEDstopsblinking.Itshouldstart
blinkingagainwhentheradioʹssquelchopens.

e. Configuration Program
TheOpenTrackerisconfiguredthroughaMicrosoftWindowsprogramavailableinthe
downloadsectionofthewebsite.Useastandardnull‐modemcabletoconnectthedevicetothe
PC.ThePCdoesnotsupplypowertothetracker,soitmustbepoweredexternally.

Connectthetrackerandstarttheconfigurationprogram.Thefirstwindowdisplayedallows
youtoselecttheCOMportthatthetrackerisconnectedto.



OverwritinganInvalidConfiguration
The‘Erasedeviceandloadnewfirmware’optionwillloadanewfirmwareimage,usingthe
defaultconfigurationsettings,withoutattemptingtoreadtheexistingconfigurationfirst.Thisis
particularlyusefulifthetrackerhasaninvalidormissingconfiguration.

TurboMode
Bydefault,theconfigurationprogramwillattempttoconnectat115,200baud.Ifyouhave
troubleconnecting,usethe‘DisableTurbo’optiontoforcetheprogramtoconnectat19,200
baud.


OpenTracker Manual - Version 1.05 – 6/25/06 page 8of 23

WarmBootvs.ColdBoot
Iftheunitisalreadypoweredonandoperatingwhenyouclickthe‘Connect’button,the
programattemptsa‘warmboot’operationtoputthedeviceintoconfigurationmode.Ifthe
firmwarehasbeencorrupted,i.e.byafailedupgrade,itmayfailtoenterconfigurationmode.
Youcancorrectthisbyperforminga‘coldboot’‐powertheunitoffandpoweritonagainafter
clicking‘Connect’.
f. Main configuration window



ConfigurationProfiles
TheOpenTrackercanstoretwoseparateconfigurationprofiles.Theprofilecurrentlybeing
shownisselectedusingthetabsatthetopofthewindowlabeled‘Config1’and‘Config2’.

OpenTracker Manual - Version 1.05 – 6/25/06 page 9of 23

Whenitisfirstpoweredon,theOpenTrackerwillalwaysstartoutusingtheConfig1profile.
Afterstartup,profileselectiondependsonthesettingsinthelower‐leftpaneofthe
configurationwindow.

Theconditionstotestareselectedusingthecheckboxestotheleftofeachcondition.Thecom‐
parisoncanbeeither‘>’(greaterthan)or‘<=’(lessthanorequalto).Clickingonthebutton
showingthecomparisonoperatortogglesitbetweenthesetwosettings.

TheAltitudeandSpeedvaluesarecomparedwiththoseindicatedbytheGPS.Onboardsensors
providereadingsforcomparisonwiththeTemperatureandVoltagefields.ADCInputreferstothe
unusedanalog‐to‐digitalconverterinputonJP8.Thepossiblevaluesare0to255,corresponding
toarangeof0to5volts.ThejumpersettingreferstoJP3.InstallingajumperbetweenpinsJP2
andJP3setsthe‘On’condition.TheGPSFixisconsideredinvalidifithasbeenmorethan20
secondssincethelastvalidpositionwasreceivedfromtheGPSunit.

Theselectedtestsarerunonceeverysecond.Iftheconditionsaremet,thenewprofileisloaded.
IfTransmitwhenswitchingtothisprofileischeckedinthenewprofile,apacketistransmitted
immediately.

Oncetheswitchtothenewprofilehasbeenmade,thecriteriainthenewprofiletakeeffect.
Anotherswitchwillnotoccuruntilthenewcriteriaaremet.Often,thecriteriaineachprofile
willbecomplementary.Forexample,Config1mightindicateaswitchwhenthejumperis
installed,andConfig2wouldindicateaswitchwhenthejumperisremoved.However,the
criteriamaybecompletelyindependentofeachother.

Ifthecriteriainbothprofilesaremetatthesametime,theconfigurationwillswapevery
second.Keepinmindthattheremaybeacertainamountofnoiseorjitteronanaloginputssuch
asvoltageandtemperature.

LoadingandSavingSettings

Afterchanginganyconfigurationoptions,youmustclickthe‘Write’buttontowritethe
changestothetracker’sfirmware.Youmayalsousethe‘SavetoFile’buttontosavethe
configurationoptionstoafile,whichcanbeloadedlaterusingthe‘LoadfromFile’button.

BasicConfigurationOptions

Callsign–Theradiocallsigntousewhentransmitting.Tacticalcallsignsmaybeused,butFCC
andITUrulesrequireperiodicidentification.Iftheactualcallsignisnotusedhere,besureto
includeitinthecommentfield.

Path–Thisspecifiesthedigipeaterpathtouse.Specificcallsignsmaybeentered(e.g.,
‘K6SYV‐10,K6TZ‐10’)butforAPRSoperationasetofcommonaliasesareusuallyused.A
OpenTracker Manual - Version 1.05 – 6/25/06 page 10 of 23

suggesteddefaultpathis‘WIDE1‐1,WIDE2‐1’.Itisrarelynecessarytouseapathgreaterthan
WIDE3‐3(requestingthree‘wide’digipeaterhops),andexcessivepathsgeneratelargeamounts
oftrafficthatdegradetheperformanceofthenetwork.Ifyou’renotsurewhatpathshouldbe
usedforyourlocalarea,checkwithalocaldigipeateroperator.Thisfieldmaybeleftblank.

TXDelay–Allradiosrequireacertainamountoftimetostabilizeontheirtransmitting
frequency,andreceiversalsorequiretimetolockon.Thisvaluespecifiesthenumberofmilli‐
secondsthetrackershouldwaitafterthestartofthetransmissionbeforeitbeginssendingdata.
Allowablevaluesare0to1023milliseconds.Settingthisvaluetoohighwillkeepthechannel
busylongerthannecessary.Settingittoolowwillpreventpacketsfrombeingtransmitted
properly.Findingtheoptimumvalueforyourradiomayrequiresomeexperimentation.

TXInterval–Howoftenthetrackershouldtransmit.Allowablevaluesare0to65,535seconds.
Thissettingwilldependonyourintendeduse.Onetransmissioneverytwominutesisaccept‐
ableformostmobilestations.Afixedstation(e.g.,asolarpoweredsitereportingbattery
voltageandtemperature)mightchooseanintervalintherangeof5to30minutes.Ifyou
requiretransmissionsmoreoftenthaneverytwominutesorso,considerusingtheSmart‐
Beaconing™optionsdetailedbelow.Specialeventswithmanytrackersandshorttransmission
intervalsshouldbeoperatedonaseparatefrequency,notonthesharedAPRSchannel.An
intervalofzerowilldisabletimedtransmissions.

SymbolTableandSymbolCode–Thesesettingscontrolthesymbolusedtoindicatethe
station’spositionwhendrawnonamap.SeeAppendixBforalistingofavailablesymbols.

Temp.Adjust–Calibrationoffsetforonboardtemperaturesensor.Thesensorusedonthe
OpenTrackerisfairlylinearacrossitsoperatingrangeandrequiresasingle‐pointcalibration.
Theeasiestwaytoaccomplishthisistosetathermometernexttothetracker.Subtractthe
temperaturereportedbythetrackerfromthetemperatureshownbythethermometer,and
enterthatvalueinthisfield.Forexample,ifthethermometershowsthetemperatureas26°C
andthetrackerreports29°C,enter–3fortheadjustmentvalue.

QuietTime–Thissettingdetermineshowlongthechannelmustbeclearbeforethetrackerwill
transmit.Eachunitisapproximately1/56second.Settingthequiettimetozerocausesthe
trackertoignoredetectedtraffic.

Text–Thisisafreeformtextfield.Anythingenteredherewillbedisplayedinthecomment
portionofthetransmissionorinaseparatestatuspacket,asselected.Keepcommentsasbriefas
possibletoavoidwastingchannelcapacity,orusethe‘Every__Transmissions’optiontoreduce
howoftenthetextissent.

Altitude,Course/Speed,Time–Whenchecked,reportthesevaluesasindicatedbytheGPS
receiver.ThetimestampmaybeinDays/Hours/MinutesorHours/Minutes/Seconds.

OpenTracker Manual - Version 1.05 – 6/25/06 page 11 of 23

GPSQuality–Reportfixtype,numberofsatellitesinuse,anddilutionofprecisioninformation
asreportedbytheGPSreceiver.

Temperature–Reporttemperatureasindicatedbytheonboardtemperaturesensorinthe
commentfield,indegreesC.

Voltage–Reportinputvoltageinthecommentfield.Themaximumvalueis15volts,andthe
minimumisthedropoutvoltageoftheregulator–typically6.7volts.

SmartBeaconing™–OriginallydevelopedfortheHamHUDbyTonyArnerich,KD7TA,and
SteveBragg,KA9MVA,theSmartBeaconing™algorithmallowsthetrackertooperatemore
efficientlybychanginghowoftenittransmitsdependingonitsspeedanddirectionoftravel.

Whenstoppedormovingataspeedbelowthelowspeedsetting,thetrackerwilltransmitata
fixedratedeterminedbythelowerratesetting.Abovethespecifiedhigh‐speedthreshold,the
higherratesettingisused.Betweenthesetwoextremes,theintervalvariesbetweenthelowand
highratesdependingonthespeed.Aturnanglecanalsobespecifiedtocausethetrackerto
transmitwhenturning.



PowerControl–Whenselected,thetrackerwillasserta5‐voltsignalonJP1beforeeach
transmission.ThiscanbeusedtodrivearelayorMOSFETtocontrolpowertothetransmitter.
Thetrackerwillpauseforthespecifiednumberofsecondstogivethetransmittertimetopower
up.Thepowercontrolfeatureisespeciallyusefulforsolar‐poweredweatherortelemetry
stations.Donotexceed25mAloadonJP1.

Timeslot–Thetimeslotoptionistypicallyusedtocoordinatemultipletrackers,especiallyfor
specialeventswheremanytransmitterswillbesharingthesamechannelwithahighbeacon
rate.Thenumberenteredselectsthetimeslot’soffset,inseconds,fromthestartofthehour.The
trackerwilltransmitatthistime,andeverytransmitintervalafterthat.Thetimeslotvalue
shouldbesmallerthanthetransmitinterval.


OpenTracker Manual - Version 1.05 – 6/25/06 page 12 of 23

UsePTTInput–Whenthischeckboxisenabled,thetrackercanbeconnectedinlinewitha
microphonetooperateinburst‐after‐voicemode.Apacketwillbetransmittedwheneverthe
microphonePTTisreleased.

PTB2Output–ThischeckboxcontrolstheoutputlevelofpinPTB2(jumperJP8).Becausethis
pinissharedwiththespareADCinput,thecheckboxisignorediftheADCinputisused.The
outputcanbeusedasanindicationoftheconfigurationprofilecurrentlyinuse.

EnableCounter–Thischeckboxenablesthedigitalcounterfunction.Whenthisfunctionis
enabled,thetrackerwillnolongertransmitimmediatelywhenJP4isshortedtoground.
Instead,itwillincrementacounterandincludethecurrentcountinthestatustext,e.g.,
‘CNT00001’.Themaximumcountis65535,afterwhichthecounterrollsovertozero.

ResetCounteronTransmit–Settingthischeckboxcausesthecountertoresetwithevery
transmission.Hence,thecountreportedisthenumberofeventssincethelasttransmission.

CounterRearm–Thisisa‘debounce’delayappliedtothecounterinput.Afteracounterevent
isregistered,allsubsequenteventsareignoreduntilthespecifiedtimehaselapsed.

InvertCarrierDetect–Usuallyusedwithmobileradios,thischeckboxindicatesthatthe
channelisbusywhenthecarrierdetectinputislow.

SuppressPTTOutonPTTIn–Thisoptionallowsthetrackertobeusedinburst‐after‐voice
modewithoutbreakinganylinesbetweenthemicrophoneandradio.PTTisnotassertedbythe
trackeruntilthemicrophonePTTisreleased.

DisableTransmitonLowVoltage–Toavoidover‐dischargingbatteries,enablethisoptionand
entertheminimumvoltageatwhichthetrackershouldoperatethetransmitter.

AllowTransmitWithoutGPSLock–Normally,whileinGPSmode,thetrackerwillnot
transmitwithoutavalidfix.Whenthisoptionisselected,thetrackerwillcontinuetotransmit
itslastknownpositionifGPSlockislostformorethan30seconds.Thisconditionisindicated
bythetext‘NOFIX’inthestatusmessage.Ifthetrackerhasreceivednovalidfixsincestartup,
nopositionwillbereported.Statustextandtelemetrypacketswillbeunaffected.Thisoption
isparticularlyusefulforapplicationslikehighaltitudeballoonsthatmayloseGPSlockafter
landing,butstillneedtotransmittobefound.

SendTelemetryPacket–EnablingthisoptioncausesthetrackertotransmitastandardAPRS
telemetrypacketaftereachpositionpacket.Thetelemetrypacketcontainsrawreadingsfrom
thethreeanalog‐to‐digitalconverterinputs,theloweightbitsofthecounter,theGPSHDOP
reading,theprofileinuse,andthestatusofthejumperinput.

OpenTracker Manual - Version 1.05 – 6/25/06 page 13 of 23

TXLevel–Thisslidersetstheaudiooutputlevel.Itisfunctionallysimilartothe‘TX’
potentiometerontheboard,butallowsdifferentaudiolevelstobesetforeachprofile.

CopyfromConfign–Thisbuttoncopiesthecontentsofoneprofiletotheother.Besureto
checktheprofileswitchingoptionsinthelowerleftpaneifyouusethisfeature–havingthe
samecriteriahereinbothprofilesisusuallynotdesired.
5. Installing New Firmware
NewfirmwarefortheOpenTrackerisfrequentlyreleasedtoprovidenewfeatures,fixbugs,or
evencompletelychangethenatureofthedevice–fromaGPS‐connectedtrackertoaremote
weatherstationorCWkeyer,forexample.

Twomethodsareprovidedtoinstallnewfirmwareimages.First,thefilesmaybedownloaded
fromthewebsitemanuallyanduploadedtothedeviceusingthe‘File’button.Thisisparticu‐
larlyusefulifyouwillbeconfiguringdevicesonacomputerwithoutInternetaccess.Second,by
clickingonthe‘Web’button,theconfigurationprogramwillretrievealistofcurrentlyavailable
firmwareimages.Selectingoneofthesewillautomaticallydownloadthefilefromthewebsite
anduploadittothedevice.



FirmwarefilesareinMotorolaS19format.Ifyoucompileyourownfirmware,theS19file
generatedbythelinkercanbeusedwithoutmodification.Interruptvectorsareautomatically
rewrittenbytheconfigurationprogram.
OpenTracker Manual - Version 1.05 – 6/25/06 page 14 of 23

6. Weather Station Operation

ConnectingtoaWeatherStation

TheOpenTrackercanbeusedwiththe1‐WireWeatherInstrumentfromAAGElectronica,the
PeetBros.UltimeterII,andthePeetBros.Ultimeter2000seriesweatherstations,includingthe
Ultimeter800and2100.InDallas/1‐Wiremode,themicrocontroller’sPTB2lineisusedasthe1‐
wiredatabus.Thissignalisavailableatpin7ofthe10‐pinheader.Apull‐upresistor,
connectedtothe5‐voltsupply,isrequiredforthe1‐wirebustofunctionproperly.Allother
weatherstationsconnecttotheserialport.

WeatherFirmwareSetup

IftheOpenTrackerhastheweatherstationfirmwareloaded,theconfigurationprogramwill
detectthisanddisplayadifferentscreenonstartup.Mostoftheoptionsfunctionaswiththe
standardtrackerfirmware.However,theweatherstationoperatesonlyinfixedpositionmode–
itcannotinterfacewithaGPSreceiver.Also,thecommenttextisalwayssentinaseparate
packetfromtheweatherdata.

The‘WindVaneAdjust’sliderisusedtocalibratethe1‐wireweatherstation’swindvane.The
windvaneshouldbepointedinaknowndirectionandtheslideradjusteduntilthedirectionis
reportedproperly.PeetBros.stationsshouldbeconfiguredin‘complete’datamode.

OpenTracker Manual - Version 1.05 – 6/25/06 page 15 of 23

7. Telemetry Operation

Withthetelemetryoptionenabled,theOpenTrackerwilltransmitanAPRS‐formattedtelemetry
packetaftereachpositionpacket:

T#011,155,218,000,000,000,00000000

Sixthree‐digitfieldsfollowthe‘T#’header.Eachfieldhasarangeofzeroto255.Thefieldsare
interpretedasfollows:

Sequencenumber:Incrementedwitheachtransmission.
ADC0:Multiplyby1.9608fortemperaturereadinginkelvins.
ADC1:Divideby17forsupplyvoltagereadinginvolts.
ADC2:Divideby51forauxiliaryanaloginputreadinginvolts.
Counter:Loweightbitsofthedigitalcounterinput.
HDOP:Divideby10forGPShorizontaldilutionofprecisionreading.

Ofthefinaleight‐digitfield,onlytwobinarydigitsareused–therightmostbitreflectsthe
jumperinput,andthenextbitindicatestheconfigurationprofileinuse.
OpenTracker Manual - Version 1.05 – 6/25/06 page 16 of 23


8. OpenTracker Circuit Details


OpenTracker Manual - Version 1.05 – 6/25/06 page 17 of 23

Theory of Operation
TheheartoftheOpenTrackercircuitisaFreescaleMC908KX8microcontrollerunit(MCU).The
MCUcontains192bytesofRAMandroughly8kilobytesofFlashprogrammemory.Itrunsat
aclockspeedof7.3728MHz.

U2isalinearvoltageregulatorthatprovidesregulated5VDCpowertothecircuit,and
optionallytoanexternaldeviceconnectedtoVext.C1andC2aretheinputandoutputfilter
capacitors,respectively.

Y1,C6,C7,andR10formtheclockoscillatorcircuit.Theoscillatorfrequencyof29.4912MHzis
dividedbyfourintheMCU’sclockmoduletoproducethebusclocksignal.

Audiooutputoriginatesatpin13oftheMCU.Thispinisconfiguredasatimerchanneloutput
andgeneratesapulse‐widthmodulatedsignalbetween0and5volts.Audiotonesare
generatedinsoftwareusingasinewavelookuptable.R2andR8limittheaudiooutputlevel,
andC2couplestheACcomponentofthesignaltotheaudiooutputatX1pin1.

Pin15oftheMCUproducesthePTToutputsignal.ItswitchesQ3,pullingtheaudiooutput
downthroughR3forhandheldPTT,andpullingX1pin3togroundforotherradios.

AnexternallyappliedPTTsignalonX1pin8willpullthePTToutputlowthroughD2,andwill
pullpin14oftheMCUlow(itisnormallyheldhighbyaninternalpull‐upresistor)throughD3.

TheaudioinputfromtheradioisAC‐coupledbyC3andbiasedbyR9.R9setsthecarrierdetect
threshold.X1pin2providesaDC‐coupledinputforradioswithasquelchorcarrieroperated
relayoutput.

R5,R1,andQ4formaninverter/buffercircuitfortheRS‐232input.TheRS‐232outputpolarity
iscontrolledinsoftware.Theoutputlevelswingsbetween0and5volts,andmaynotbe
compatiblewithallRS‐232devices.

U3isatemperaturesensorwithanoutputof10mVperKelvin.R6limitsitsinputcurrent,and
itsoutputdrivesoneoftheanaloginputsontheMCU.

R7andR11formavoltagedivider,theoutputofwhichisonethirdofthesupplyvoltage.This
voltagedrivesanotheranaloginputontheMCU.

TheLEDisdrivenbyahigh‐currentoutputlinefromtheMCU,throughcurrentlimiting
resistorR4.LoweringthevalueofR4willincreasethebrightnessoftheLED.
OpenTracker Manual - Version 1.05 – 6/25/06 page 18 of 23

9. Assembly Notes Pictorial


1.Inventoryandseparatepartsforeasier
handlingduringassembly


2.Startwithmicroprocessorsocketand
10‐pinheader


3.Solderafewparts,solder,andthenclip
offleadsclose.Lookforbridgesandshorts
asyougoalong.


4.Close‐upofC6,Y1,C7–notehow
insertingY1mightbetrickyifC6andC7
arebothalreadyinplace


5.Finishedproject.InthiscaseR3hasbeen
leftoutasthisunitwillbeusedwitha
mobilerig




OpenTracker Manual - Version 1.05 – 6/25/06 page 19 of 23

Appendix A – Test Procedures

a. Measurements

Disconnectthetracker,removeU1fromitssocket,anduseanohmmetertocheckthefollowing
connections.Nominalvaluesareapproximate.

ConnectionNominalValueCircuitDescription
U1‐1toU1‐162.6kΩPowertoGround
U1‐9toU1‐1010MΩCrystaloscillator
R8outerleads10kΩTXleveladjustpot
JP2toJP830kΩVoltagedivider
U1‐5toU1‐17.5kΩTemperaturesensor

WithU1removed,connectthetrackertoitspowersource.UsingU1pin1orJP2asground,
checkthefollowingvoltages.

ConnectionNominalValueCircuitDescription
U1pin165V±0.25Voltageregulatoroutput
U1pin510mV/KTemperaturesensor:2.95V=295Kelvin=71.3°F
JP86.7to35VVin
U1pin61/3Vin Voltagedivider

Removepower,re‐installU1,andpowerupthetracker.Withatypicaldigitalvoltmeter,U1
pins9and10shouldindicateapproximately2.4Vand2.2V,respectively.Afrequencycounter
oroscilloscopeshouldshowa29.4912MHzsignalatthesepins.Absenceofthissignalindicates
aproblemwithU1orthecrystaloscillator.





OpenTracker Manual - Version 1.05 – 6/25/06 page 20 of 23