PIC-A-STAR - UCoz
PIC-A-STARINDEX by Peter Rhodes, BSc, G3XJPSOFTWARE TRANSMITTER AND RECEIVERPART 1PART 10DSP Assembly assembly and testGeneral introductionTypical Tx/Rx block diagramPART 2Software block diagramHow the software works; is packaged; and can beobtainedPART 3PCB Manufacturing processComponent list for Timer, Status, IF, DSP boards;and assembly thereofPART 4Super VOXTimer board circuit diagram and PCBPART 5Circuit diagrams for DSP mother;CODEC daughter boardsPART 12PicAdapter and Status board circuit diagrams.RS232 wiring.PART 13Possible stereo amplifierPicAdapter and Status PCB component location andartworkPART 14Some Pic 'N' Mix suggestionsProcessor andPART 6Component location for DSP mother board.DSP board test processPART 7Overview of G3XJP Tx/RxDSP board construction techniqueDSP board PCB artPART 8IF board description and circuit diagramPART 9IF board component layout and PCB artDSP Assembly construction G3XJPPART 11STAR UI backgroundPossible Tx/Rx layout and front panelPART 15DSP operational features and usePART 16Magic Roundabout circuit diagram, optionsPART 17Magic Roundabout PCB component layout and artOverall STAR Rx performance numbersPART 18Band Pass Filters - discussion and circuit diagramPART 19Band Pass Filters - PCB component layout andartworkPART 20ConclusionPIC-A-STARPage 1
PIC-A-STARPart 1 by Peter Rhodes, BSc, G3XJPSOFTWARE TRANSMITTER AND RECEIVERTHIS IS A detailed constructionproject aimed at those of modestexperience who would like to enhance both their craft and technology skills.At the outset - like me - it may well bethat you don't have the skills or knowledgeto build this project. By the end, you willhave. That is, as I see it, the whole idea.By design, this is a project without end.From my perspective, it is the basis foryears of happy building to come - and is myfirst investment in a new core transceiverplatform in some 25 years. A glance at thephoto tells you why I needed a new one.From your perspective it is a source ofideas for improving an existing transceiver not least, replacing the back-end with apowerful Digital Signal Processing (DSP)capability. There are also some craft techniques for handling small-size high-functioncomponents. So, there is something in thisfor everyone with an eye on the selfeducation requirement of their Licence.POSITIONING DSPYOU MIGHT reasonably expect the authorof a DSP project to have some seriousknowledge in the field. So would I! Actually in many ways it is important to get thispublished before I acquire more thanenough to be merely dangerous.If, like me, you are at least in your late50's it is unlikely that DSP theory featuredeven in a formal engineering education.And if equally like me you have neverworked in the engineering profession thenyou could reasonably start from the positionthat DSP is some kind of black magic whichyou could never understand in a life-time oftrying. You might well be correct in thisassumption because some of the theory isindeed very heavy.But my personal discovery was that youdon't need to understand DSP at other thana superficial level to be able to build it athome and to use it.From a position of not being able to spellDSP, it took me two weeks to get my firstDSP receiver working. The attraction isthat everything since then has been incremental and I have not been off-air for asingle day. Design mistakes - and therehave been many - have cost me my time butnever any money - which is about perfectthat they can be built on the kitchen tablewith no access to professional facilities.Otherwise, it would not be amateur radio.This one is no exception - though I havehad to acquire new skills and hone them tothe point of repeatability in order to buildsome of the hardware. This is all part of theadventure, part of the fun. And of coursethose skills have general application so theyopen up new avenues for the future.A simple (and inexpensive) technique formaking precision PCBs will be covered which includes mounting a 48-pin chip witha mere 0.5mm interval between pins. Andyou get to practice on a really easy one of128 pins by 0.8mm first. If the prospect ofthis puts you off, I really can't help. If itsparks a can-do spirit of adventure then weare in business.INSPIRATIONTHREE THINGS made this project possible. In the order in which I found them: "The Scientist and Engineer's Guide toSUMMARYDigital Signal Processing" by Steven W.THE HEART of PIC-A-STAR is the DSPSmith. This book is a little gem. If youmodule. This provides both the back-endflick through quickly you will see copiousreceiver functionality - as well as SSB/CWexamples and illustrations. What you dogeneration on transmit. The bottom line isnot see is lots of equations and impenetrableabsolutely superb audio quality on bothnotation. I need just one quote:- " [thistransmit and receive. If you want to test thebook] is written for those who want toformer, come on the homeuse DSP as a tool, notbrew net frequency (seea new career." Myphoto) any day aroundkind of book!lunch-time where you will The Analog Defind at least one STAR invices web-site [1].operation most days. If youThiscontainsawant to test the latter thenwealth of both theoyou will just have to makeretical and practicalone.information - andBeing implemented byspecifically the elecsoftware, it provides thetronic version of theopportunity to address bothabove book.Mostabsolute performance as wellvaluable to me wereas the delights of operationallots of DSP codeconvenience - at zero increexamples for theirmental cost. This is preADSP-218x procescisely the basis for futuresors. The first incardevelopments, but the funnation of STAR wasdamental functionality tobuilt by six of us ongether with some bells andtheirADSP-2181even the odd whistle has Early integration testing. Bottom left is my Third Method transceiver (borrowed front- EZLITE evaluationbeen in daily use here for end and PA), top right is Pic ′N Mix DDS still on its original breadboard (injection and board which had beabout nine months. This is controls) - and in the middle is the new DSP module under development. Note that Pic come somewhat athe project on offer - but by ′N Mix provides all the transceiver controls, leading to a clean and compact front panel.standard over thethe time you get there it willfor a hobby. So this lends itself to a learnyears. Then over one fateful weekend whenhave moved on.as-you-go approach. In other words, unlikethis project was 'finished', its price wentPIC-A-STAR is explicitly designed to beconversational French, you don't have tofrom 90 to 275 - which spurred the chalupgraded over the web, so there will nolearn a lot before you can even get started.lenge to home-brew a compatible and reincremental DSP enhancement costs.SKILLS AND FACILITIESproducible DSP board.A REQUIREMENT of all my projects is DSP-10, a 2m DSP transceiver project G3XJPPIC-A-STARPage 1
published by QST in Sept-Oct 1999 - andreviewed in RadCom, Feb 2000. Althoughfeatured for VHF/UHF applications, theDSP core is totally universal. This projectwas designed by Bob Larkin, W7PUA [2]and I am indebted to Bob not only for theinspiration for this project but for a significant amount of advice and help - includingsome code written specifically for PIC-ASTAR. Above all, Bob showed it can bedone and whenever I get into problems, hismaterial is the first place I look for understanding.INTEGRATING PIC-A-STARTHE DSP MODULE - designed to combinewith the Tx/Rx RF stages of your choice operates at a final IF of 15kHz as shown inFig 1. This is a high enough frequency tomake it immune from image responses yetlow enough to be affordable. And it is not aDSP audio add-on, which coming after theproduct detector will always struggle.RF STAGESYour HF IF can be derived from any reasonable transceiver front-end. My ThirdMethod Transceiver [3] and G3TSO'sModular Transceiver [4] have both beentested as representative - and there are lotsof them out there. CDG2000 looks like apowerful approach and their front-end couldwell be my next increment. The choice willsubstantially determine the overall receiverstrong-signal handling capability - but notthe basic effectiveness of downstream DSP.IF STAGESIn principle (and possibly in practice) youcould modify an existing IF board so that itsproduct detector produced a 15kHz outputinstead of straight audio but I don't recommend it in the long run. You would have tocompletely rebuild all the audio filtering topass 15kHz both on transmit and on receive.And unless the crystal filter were wider thanusual, you would be passing up the opportunity to enjoy the pleasures of fullbandwidth SSB reception under good conditions. Some of the older IF amplifiers arenot noted for their noise figure, so, to cut along story short, this design includes an IFboard built for the job.Details of this follow later, but it onlyneeds a modest roofing filter (at any HF IFof your choosing) since all the serious filtering is implemented in DSP.CONVERSION INJECTIONYou won't be surprised to see Pic ′N Mix[5] used as the injection source to mix fromRF to your chosen HF IF. This is not mandatory but my records show 281 of them outthere, so it is a non-trivial population.Existing (or typical) HF Tx/Rx RF stagesCOMMAND AND CONTROLYou need the ability to command the DSPfor all the functions normally associatedwith front-panel controls. You may besomewhat surprised to see Pic ′N Mix usedfor this purpose as well.A small adapter board is used to fit amore versatile and powerful PIC - whichnot only controls all the original DDS capability but extends the existing keypad, display and tuning knob to control all thetransceiver features.Although highly recommended, use ofPic ′N Mix is not mandatory. As an alternative, you can use your PC to load and control the transceiver - and a BASIC utility isprovided to achieve this.PIC-A-STAR FEATURES IN BRIEF SSB and CW detection and generationa bank of high-performance Rx filtersimpulse noise blankingnon-coherent noise reductionauto-notch heterodyne(s) removalvariable AGC decay timesynthetic stereo receptionadjustable RF clipping on transmitvery fast VOX and QSK operationthe flexibility to change!Pic 'N' Mix DDS small adapter boardBand selectInjectionLatchesStatus LEDsPALPF x 6PostampMixAD9850DDS6-digitdisplayBPF x 9Knob shaftencoderDSP Assembly 15kHz IF board DSP Processor boardKeyPad (4x3)PICMixJ310SerialEEPROM(DSP code)Xtal filterAD603Xtal osc10.7MHz 15kHzeg 10.7MHz2.8-15kHz wide15kHz IFBar-graph ormechanicalAFampSimple20kHzLPFRS232AFampMicPTT'S' meterAGCDSP code at power-onthen User commandsNew DSP code releases(over the web) from yourPCvia RS232 linkDACRight inMicampLeft inRight outDSPProcessorboardLeft out(2-channel)Timer boardStereoampLST/RControls/times T/Rvoltage and changeover switchingPICDriverKeyFig 1: A typical transceiver incorporating PIC-A-STAR at a final IF of 15kHz. See text for a discussion of the major hardware elements. G3XJPPIC-A-STARPage 2
REFERENCES[1] www.analog.com[2] www.proaxis.com/ boblark/dsp10.htm[3] RadCom June-October, 1996[4] RadCom Oct-Nov, 1988[5] RadCom Jan-May, 1999 G3XJPPIC-A-STARPage 3
PIC-A-STARPart 2 by Peter Rhodes, BSc, G3XJPSOFTWARE TRANSMITTER AND RECEIVERSOFTWARE is this month's topic, namely anoutline of what it does, how it works, how itis packaged and how you obtain it.The essentials of programming PICs hasalready been covered [6] so this project willconcentrate on the DSP dimension.PIC-A-STAR DSPILLUSTRATED in Fig 2 is the functionality implemented in software. You will haveseen not dissimilar block diagrams implemented in analogue hardware - but not atthis price and not inside a 28mm2 chip!Actually, there is an intrinsic overhead,namely that the analogue signals need converting to digital form before processing and back to analogue after. This is the purpose of the CODEC (encoder/decoder)referenced on several inputs and outputs and is implemented on a separate chip.The greatest appeal of the software approach, not least to the amateur, is theMixLPF3kHzRF gain15kHzRx IF15kHzosc (sin)GaincontrolUSBLSB15kHzosc (cos)MixLPF3kHzTIME IS OF THE ESSENCEThe basic understanding you need in orderto grasp how DSP works is to note that time90 phaseshift /fromCODECClip amountSSB PowerGaincontrolLPF18kHzUser commands fromPic 'N' Mix or PCCommandvia RS232 linkinterfaceexternalAGC toDACDecay yBetaAutonotchNoisereducerRFClip cstereoKey h15kHzoscVOXpredelay15kHzosc (sin)Mix15kHz"stereo"AF toCODECT/RcontrolLPF2.8kHzDelayMic AFfromCODECVOXVOXgainMix15kHzosc (cos)AllcontrolsStereoeffectAnti-VOXKeyinggate90 phaseshiftAFgainSSBSSBCWDelayCW Power15kHzTx IFFilter bank:'Wide''Medium''Narrow'(twice)Pulsewidth& levelQSKpredelayGaincontrolis the critical commodity. Every functionalbox in fig 2 takes time to execute. So doesevery individual instruction that goes tomake up that functionality.This would be of little concern were itnot for our old friend Nyquist. He statedthat in order to faithfully process a signalyou must sample it at twice (at least) therate of the highest frequency present.For example, the incoming Rx signal isaround 15kHz and so needs to be sampledat 30kHz or more. In fact, 48kHz is used toprovide a useful margin.The consequence of this is that havinggrabbed one sample you have no more than20.83µs (by simple arithmetic) to do all theprocessing required before you have to getback to handle the next one. (Actually ifyou don't achieve it, the processor will interrupt whatever you are doing and dragyou back, so important is it.)So just how much processing can beachieved in 20 millionths of a second? TheADSP-2181 processor in this design executes an instruction in 30 nanoseconds. Thesimplistic answer is therefore 666 in-flexibility to change the line-up at a touchof the keyboard, so to speak. This allowseasy experimentation (or overt tinkering, ifyou prefer) since at any time you can abandon the change and go back to the previousversion. There are other subtleties.For example, you will find five 15kHzoscillators scattered around the diagram. Infact their frequency changes depending onmode ie USB/LSB/CW. In DSP softwareterms the sinusoidal oscillator is simply asubroutine. To invoke it, all you need do istell it what frequency/phase you want onany given occasion - and it is done.Another example is the 'delay' in the Rxfront-end image-cancelling I/Q mixer. Inone path there is a 90 phase shift, in theother a delay. The latter arises because ittakes real elapsed time to produce the phaseshift, so an equal amount of time has to be'wasted' in the other channel to maintainthat phase gainGaincontrolReceiveTransmitControlUser controlFig 2: Software block diagram of PIC-A-STAR DSP functionality. Not shown are simple on/off switches associated with VOX, noise blanker, autonotch, noise reducer and the RF clipper. The filter bank also has an off (ie bypass) switch to give a net maximum bandwidth of some 3kHz. G3XJPPIC-A-STARPage 1
structions-worth. But this is far from thewhole story. During one processor cycle itcan, for example, fetch two 16-bit numbers,multiply them to give a 32-bit product andadd the result to a 40-bit accumulator. ThisMAC (Multiply & Accumulate) instructionis the essence of filter implementation andis critical because you need to loop aroundit many times. Meanwhile, in the background, the processor is also organisingdata samples in and out of the CODEC aswell as handling any serial communicationsport activity.All these features (and more) characterisea processor capable of serious real-timeDSP.Fig 3 shows a snatch of PIC-A-STARcode so you can visualise just how muchradio you get from each line of code.MULTI-RATE PROCESSINGThere is a more structural solution to theissue of buying some time - which equallyderives from Nyquist. Namely, once the Rxsignal has been mixed down to audio youan English word) leads to some complication in describing the various modules.The context will become clearer once thehardware functionality has been covered.Suffice it to say at this stage that from anoperator's perspective the system is totallytransparent ie you just switch it on, waitabout 20 seconds (as if for the valves towarm up) and then use it. The softwarecomes in the following modules:DSP BOOT UTILITYThis code resides in PROM on the DSPboard. At power-on time, besides runningsome basic hardware checks, it manages theon-board serial port to load the target DSPcode. This utility was written by BobLarkin, W7PUA for PIC-A-STAR based onthe original AD code.DSP TX/RX CODEThis runs on the DSP board and providesthe core functionality as in fig 2. It needs tobe loaded at power-on time, a processwhich takes some 20 seconds. Subsequentto loading it, you also need to be able tocommand it.{ Fetch Rx sample via CODEC and place in register mx0 }mx0 dm(Rx in buffer);{ and fetch current RF gain value and place in register my0. }my0 dm(RF gain);{ Multiply the two together to give a gain-controlled value }mr mx0 * my0 (SU);{ and keep the gain-controlled signal in register my0. }my0 mr1;{ Fetch the phase incremented value of LO and place in register ax0 }ax0 dm(LO phase);{ Pass the phase value to sin to get instantaneous sinusoid amplitude }call sin;{ and mix (ie multiply) it with the signal in register my0 }mr ar*my0(SS);DSP LOADERThis is a QBASICutility which runs onyour PC. It is written in very basicBASIC to enableyou to adapt it orport it if you wish.It has two distinctalternativefunctions: To load andFig 3: Some early lines of code for the receiver. Yes, the last line truly is subsequently coma mixer (otherwise known as a product detector). The code continues by mand the DSP codeadding 90 to the phase value so that a call to sin returns the quad- directly to the DSPrature LO - which is again mixed with the signal. After phase-shifting,board, via a COMthe outputs of the two mixers are then literally added to give USB - orport and a 9.6kBsubtracted for LSB.serial link.no longer need to process it at the 48kHz To load a new (or, of course, first)rate. Twice the audio frequency is fastrelease of the DSP code to the PicAdapterenough.board (see next) in Pic ′N' Mix. SubsePIC-A-STAR runs audio processing atquently, Pic ′N' Mix automatically loads the8kHz - by grouping the audio functions intocode at power-on time - and provides the6 blocks and running one of them - but eachcommand user interface.in turn - during 6 successive 20.83µs timeThese two alternatives are not mutuallyslots. At the end of each slot the data isexclusive. For early testing and use, theagain processed at 48kHz because that isformer gets you going quickly. The latterthe sample rate used by the CODEC forfrees up your PC and in my view, gives aoutbound signals also.much cleaner user interface - albeit with aThis whole approach is known as "multilittle practice. The choice is yours.rate processing"; getting the sample rate(There is a further option here. Youdown, "decimation"; and getting it back upcould build a dedicated controller using anyagain, "interpolation". A similar process isprogrammable device with an RS232 capaused on the Tx side.bility. The command syntax is simple andSo you can see that all the way along thealso provided - and is in any event selfline Nyquist is satisfied - and so am I beevident from the QBASIC code. With somecause there is plenty of time for some exoticloss of maintainability, you could also burnas well as the more mundane processing.the entire Tx/Rx code into the bootPROM/EPROM.)SOFTWARE PACKAGINGTHE DESIRE to provide choice and flexibility but above all upgradability (if that is G3XJPruns on a 16F870 (which replaces the present 16x84) to provide all the original DDScontrol functionality of Pic ′N' Mix and inaddition, it now int
PicAdapter and Status board circuit diagrams. RS232 wiring. PART 13 Possible stereo amplifier PicAdapter and Status PCB component location and artwork PART 14 Some Pic 'N' Mix suggestions PART 15 DSP operational features and use PART 16 Magic Roundabout circuit diagram, options PART 17 Magic Roundabout PCB component layout and art
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Chapter 7 - The Microchip PIC 129 7.0 The PICMicro Microcontroller 129 7.0.1 Programming the PIC 130 PIC Programmers 131 Development Boards 131 7.0.2 Prototyping the PIC Circuit 132 7.1 PIC Architecture 134 7.1.1 Baseline PIC Family 134 PIC10 Devices 135 PIC12 Devices 135 PIC14 Devices 138 7.1.2 Mi
Aug 27, 2019 · Pic-3 Pic-6 Pic-2 Pic-5 Pic-1 Pic-4 ATTENTION: Make sure that the right wheel (marked R) is attached to the right side and the left wheel (marked L) to the left side (seen from behind the cart in driving direction), as the wheels have built-in one-way clutches. The caddy w
PIC K150 Manual 1-10 The USB PIC K150 microcontroller programmer Hardware version V2.0 File version V2.0 Product Image. Product Description K150 is the latest of a low-cost high-performance PIC programmer, support most popular PIC chip bur
tion of normal logic chips can be squeezed into one PIC program and thus in turn, into one PIC microcontroller. Figure 1.1 shows the steps in developing a PIC program. PIC programming is all to do with numbers, whether binary, decimal or hexa-decimal (base 16; this w
a PIC microcontroller by serial communication. Serial communication between the PC and the PIC microcontroller is enabled by using a DB-9 serial connection between the PC and a PIC development programmer that hosts the PIC microcontroller. Two widely used PIC development programmers are Microchip’s PICS
The PIC Architecture The Basics of the PIC architecture Although it is not essential to know every last detail of how the PIC microcontroller works, it helps to have an understanding of memory, ports, interrupts, and peripherals and how they all interact. Memory The PIC has 2 types of memory: ROM (Read Only Memory) and RAM (Random Access Memory).
1. Suppose star B is twice as far away as star A. A. Star B has 4 times the parallax angle of star A. B. Star B has 2 times the parallax angle of star A. C. Both stars have the same parallax angle. D.Star A has 2 times the parallax angle of star B. E. Star A has 4 times the parallax angle of star B.
