Fullscreen HTML5Med Res (??MB)HTML4

MORE FUN WITH THE PICAXE – PART 7 Get that fat cat code purring . . . In an era when even modest home PCs demand 128 MEGA bytes of RAM, the microscopic 128 bytes of Picaxe–08 memory seems almost laughable. To put this million times ratio into perspective, it’s roughly akin to the price difference between a car and a peanut. Of course, with resourceful design, even 128 bytes may not be peanuts! A lthough PICAXE microcontrollers don’t require solid programming skills, it’s crystal clear to many users (myself included) that such devices, using “ software to tame the hardware”, look to be the future of many electronic circuits. Most Picaxe designs (including mine) evolve under “cut and try” incremental programming, and parts drawer fossicking for, say 82nF capacitors and 680kΩ resistors in a traditional timing circuit, can be replaced by convenient and versatile code-tweaking instead. Layouts can be smaller and cheaper too, and upgradable later without laborious unsoldering. So – you want to be part of this “Flash” revolution then? You’d better take note of some basics! If you yearn for more than simple “08” tone output or LED flashing, coding care and economy is obviously crucial. And it’ll help develop good design habits that may carry over to larger microcontroller applications. www.siliconchip.com.au Many real-world electronic and software engineering projects, just as in other fields, are characterised by skills subdivision, such that teams may work on the display, while others may be slaving away with power supplies or user interfaces. Ultimately these have to be seamlessly integrated into the final product, or much fist shaking and gnashing of teeth can occur. It’s similar to building a house and coordinating tradesmen – of course you don’t want concrete slabs poured before services like drains are first installed. Perhaps the Golden Rule here is to    DOCUMENT YOUR CODING. Such comments (indicated by ‘ before a remark) not only inform others about your actions, but allow you to be reminded about things when later (re)viewing your work. These comments do not add to any program bulk, but are saved along with the program to your PC. If you’re a two-fingered typist re- by Stan Swan Clever code can purr along with the limited 128 bytes of an “08”! entering programs by hand (rather than a copy-and-paste from a web page listing ), comments don’t strictly need to be included. Styles vary but it’s common to add such ‘remarks on the same line as the action. Thus SLEEP 300 ‘enter low power sleep mode for 300 secs = 5 mins No doubt you’ve noted the initial preamble comments on our previous listings too. These “abstracts” make for convenient spots for parts lists, authors, web sites, dates and versions – the latter point a crucial feature of course! Others may judge your skills by your comments, much as electronic projects are often judged by neatness of the hook-up wiring or PC board design. Indenting a set of instructions, especially a loop, is also accepted practice since it quickly allows visual grouping. Using ‘—— spacers may help too. Points so far are pretty much common sense but GOSUB/ RETURN – command pairs may need explanation. August 2003  77 LEDSOS.BAS (Also downloadable from: www.picaxe.orconhosting.net.nz/ledsos.bas) ‘Switchable LED or SOS flasher for Aug 2003 SiChip PICAXE-08 article V 1.0 26/6/03 ‘Connect 3 ultra bright white LEDs directly to PICAXE pins 4,2 & 1 + common ground. ‘Switch to pin 3 may need pulldown resistor (10 k ?) since tends to float high ‘Just a single LED could be used, but 3 give greater light output even though each‘-is actually lit sequentially & human “persistence of vision” perception exploited. ‘Additional security results,since if 1 or 2 LEDs damaged or blown at least 1 works. ‘No dropper R’s as PICAXE 20mA source limit each pin is inside white LED 30mA specs. ‘Extra driver transistor could be used to give ~100mA pulses?(Ref PWM “SiChip” 4/03) ‘New command here =GOSUB,which allows common routine streamlining,thus memory saving. ‘Maybe alter pulse duration,but 700 =7millisec seems highest flicker free pulse rate? ‘Just 96 bytes used, so scope for other lighting effects- chasers/random/1-2-3 on etc ‘Maybe “lost in the bush” beacon flasher once every 5 secs = prolonged battery life! ‘3xAA batteries (4.5V) had ~16mA max drain when pulsed ~60 hrs life (& longer on SOS) ‘ Via Stan. SWAN (MU<at>W,New Zealand) => s.t.swan<at>massey.ac.nz <= ‘Lines beginning ‘ are informative program documentation & may be ignored if need be. ‘Program available for web download => www.picaxe.orconhosting.net.nz/ledsos.bas ‘Further “08” Morse ID refinements (35 chs !)=> www.picaxe.orconhosting.net.nz/morse.bas ‘——————————————————————————————————————— ledtrio: ‘routine to pulse all 3 LEDs to prolong battery life if pin3=1 then ledsos ‘if pin 3 switch is low(0) just “steady” light ouput gosub pulse ‘access common LED pulsed lighting routine goto ledtrio ‘loop back if switch set for steady light out still ‘-——————————————————————————————————————ledsos: ‘emergency routine to send endless SOS .../—/... for b1= 1 to 3 ‘morse S = dit dit dit for b0= 1 to 4 ‘short hold on for each “dit” element gosub pulse ‘access common LED pulsed lighting routine next b0 ‘loop to hold on duration variable pause 200 ‘200ms pause between each morse element next b1 ‘repeat so 3 flashes generated pause 500 ‘1/2 sec delay between each morse character ‘——————————————————————————————————————— for b1= 1 to 3 ‘morse O = dah dah dah for b0= 1 to 15 ‘longer pulse hold on loop for each “dah” gosub pulse ‘access common LED pulsed lighting routine next b0 ‘loop to hold on duration variable pause 200 ‘200ms pause between each morse element next b1 ‘repeat so 3 flashes generated pause 300 ‘1/2 sec (total) delay between each morse character ‘————-——————————————————————————————————- for b1= 1 to 3 ‘morse S = dit dit dit for b0= 1 to 4 ‘short hold on for each “dit” element gosub pulse ‘access common LED pulsed lighting routine next b0 ‘loop to hold on duration variable pause 200 ‘200ms pause between each morse element next b1 ‘repeat so 3 flashes generated pause 500 ‘1/2 sec delay between each morse character ‘——————————————————————————————————————— pause 1500 ‘2 second pause between SOS sending goto ledtrio ‘recommence program from start ‘——————————————————————————————————————— pulse: ‘subroutine to rapidly sequentially pulse all 3 LEDs pulsout 4,700 ‘pulse pin 4 700 x 10 microsecs =7000us =7ms pulsout 2,700 ‘pulse pin 2 (Perhaps try varying mark/space effects-) pulsout 1,700 ‘pulse pin 1 (using high 4:pause 5:low 4:pause 50 etc) return ‘go back to program point where subroutine began 78  Silicon Chip These act as an elegant GOTO, and are seen as the heart of efficient structured programming, since they allow common routines to be referred to and actioned as need be, with a return back (to the next program line) on completion. It’s similar to maybe “going on auto” when asked to put out the garbage while watching TV. LEDSOS.BAS The subroutine in the sample LED flashing program at left, giving out either a steady light or switched SOS, is called up as needed to give a common “pre-wound” pulsed LED instruction set rather than wastefully say the same thing three times elsewhere. Pulsout commands here were selected to minimise circuit current drain, while giving the brightest light with the least flicker. A Lux meter (eg, DSE Q-1400) may prove invaluable for this, since the human eye rather falls short when judging illumination changes. As an aside from microcontrollers, ultra-bright white LEDs look to be the best lighting development in 100 years (and I’m related to Swan of 1880s carbon filament lamp fame too!) Their light output (typically now a dazzling 5600mCd for even “cooking” versions), almost unlimited life, ruggedness, high efficiency and (now) cheapness make traditional hot filament lamps near obsolete for portable work. Although white LEDs typically draw 30mA at 3.6V, the 20mA Picaxe source limit allows them to be driven directly from output pins (here 4,2,1) at slightly reduced brightness. A trio of driver transistors, as featured in the earlier pulse width modulation (PWM) motor controller, (SILICON CHIP April 2003) could perhaps boost this for brief 100mA pulses. Note the new 10mm types used here give out no more light than normal Any simple 2-wire conductor will pass Picaxe serial display data. Use the D9 pin 2 for the signal, with ground pin 5. www.siliconchip.com.au 5mm types, but seem to “have more presence” according to one observer. Being larger, they’re much easier to find too – the transparent 5mm types are almost invisible when dropped on a carpeted floor! Morse in the 21st century? Although now very much the domain of amateur radio CW diehards, Morse code remains invaluable for beacon/lighthouse ID and emergency signalling – perhaps by flashing a (LED) torch or even knocking SOS on the wall. Hidden transmitter outdoor “fox hunts” sending Morse remain highly popular too. More to the point for program economy insights, Morse dit/dah characters lend themselves to elegant analysis. Somewhat as a joint effort challenge (and inspired by an old BASIC Stamp program), Eric van de Weyer and I have managed to squeeze up to 35 Morse characters into an “08”. Without such “crunching”, it’d be taxing to even fit “Leo” [.-.. . ---] into 128 bytes ! Practising what I preach, the program listing overleaf (MORSE.BAS) is copiously commented, with even Morse characters themselves included for those who forget (or those who never knew them!). Audio output is just from our piezo attached at pin 0, while the 10kΩ pullup resistor fitted to pin 3 also remains. Driver transistors could be used to key a transmitter for more powerful work. The SLEEP command used here, although only about ±1% accurate, causes a low power resting mode to be entered, which provides useful battery life extension. The syntax is obvious ex. SLEEP 60 will awake after 60 seconds, SLEEP 3600 after an hour Yes, it’s the same old protoboard layout . . . or is it? That’s right, it is now rather simplified. (The 10kΩ & 22kΩ resistors are only required during programming.) MORSE.BAS Enough of the 19th century – we’re in the Internet age. PICAXE serial data output (mentioned in the last article) also ends itself to message display. Although small LCD panels abound (mostly Hitachi-style 16 characters x 2 lines), these usually need driving with a parallel data stream. Logic ICs can be wired to provide SIPO (Serial In Parallel Out) shift registers, but these naturally may daunt users with simple display needs. Several options have presented themselves, all of which will just need a simple 2-wire serial lead from the www.siliconchip.com.au Following the finding (detailed last month ) that the piezo speaker can be left permanently attached to pin 0, the PICNIK box wiring has been adjusted to suit. The now idle jumper is here used to switch input 3 high or low via a 10kΩ pullup resistor. August 2003  79 Picaxe output pin in use and ground return. 1. Purchase and assemble the Rev. Ed AXE033 LCD 2-part kit. (available in Australia and NZ from Microzed or their resellers). This comes with decoding electronics on board, plus a socket for a Real Time Clock (RTC) chip option that can be used to trigger program events. Additionally up to 7 prepared messages can be organised and saved on this LCD board for easy recall– hence sparing the driving Picaxe the associated memory storage overhead. Yah! If your project can stand the cost (A$44) this LCD certainly will greatly enhance it. However you’ll need to have good soldering skills to assemble the rather fiddly kit (the instructions are microscopic!). A higher voltage 6V supply will also be needed, since the now-normal Picaxe 4.5V supply will not bring up the LCD image. Grr ! 2. As an LCD workaround, the Programming Editor displays a mini serial terminal when F8 is pushed, using a signal lead (NOT the normal programming one) from the chosen Picaxe output pin and ground. This display text is wider than the 16x2 LCD display, but may be valuable for initial display work. 2002 versions of the Picaxe Editor (Ver. 3.0.3) also offer a more graphical display when F9 is pushed MORSE.BAS (Also downloadable from: www.picaxe.orconhosting.net.nz/morse.bas) ‘PICAXE-08 memory workout demo via Eric van de Weyer & Stan.SWAN Ver 1.02 27th June 2003 ‘For Silicon Chip August 2003 PICAXE article. Author - Stan.SWAN => s.t.swan<at>massey.ac.nz ‘Ref. Edwin.C => chick<at>chickene.freeserve.co.uk -June 2002 RSGB “RadComm” “28” version too ‘Program (derived from a Basic Stamp-1 idea ) sends short repeating Morse Code ID message ‘———————————————————————————————————————— ‘Almost unbelievably up to ~35 Morse characters can be stored in the tiny PICAXE-08 RAM ! ‘Output here just simple Piezo speaker at PICAXE Pin 0, but could be used to key a Tx etc ‘Only other component needed = 10k pull up R pin 3 to +ve rail to avoid “floating” 1/0 ‘Note - although now near obsolete for messages,International Morse Code ( CW ) still has ‘wide use for beacons etc since decoding can be via eye or ear,& even unskilled observers ‘can thus “read” simple IDs & status at just a few (5?)words per minute.Of course sending ‘SOS via torch etc still suits emergencies! Scouting days now long past? Morse chs.are... ‘A .– B –... C –.–. D –.. E . F..–. . . . . . . . . . ‘G ––– H I J ––– K– – L.–.. . . . . ‘M –– N – O – –– P – Q–– – R.–. . . . . . . . . . ‘S T – U – V – W ––– X–..– . . . . . . . . . ‘Y– –– Z –– 1 –––– 2 – –– 3 –– 4....– . . . . . . . . . . . . . . . ‘5 6 – 7 –– 8––– 9–––– 0––––– ‘ Full stop . – . – . – Comma – –. . – Slash – . . . . – ‘ ‘By tradition 1 dah/dash = 3 dits/dots with letter space = 3 dits & word spacing 7 dits ‘ ‘How DOES this work !? Each ch.to be generated is programmed in as a number whose binary ‘equiv. then generates the code ! The 5 MSBs (Most Significant Bits =LHS) represent dots & ‘dashes, with dit=0 & dah=1. The last 3 LSB (Least Significant Bits = RHS) indicate how ‘many elements in a ch. Hence V=00010100 (100 =4 elements). Bit 5 is meaningless here. ‘Converting to decimal yields 20. Another ? K=10100011 = decimal 163 (011= 3 elements) ‘Here’s is a list of these characters (abrev. as ch. in comments) & their equiv. number ‘———————————————————————————————————-————‘A - 66 B - 132 C - 164 D - 131 E-1 F - 36 ‘G - 195 H-4 I-2 J - 116 K - 163 L - 68 ‘M - 194 N - 130 O - 227 P - 100 Q - 212 R - 67 ‘S - 3 T - 129 U - 35 V - 20 W - 99 X - 148 ‘Y - 180 Z - 196 1 - 125 2 - 61 3 - 29 4 - 13 ‘5 - 5 6 - 133 7 - 197 8 - 229 9 - 245 0 - 253 ‘= - 141 / - 149 . - 86 , - 206 ‘ ‘Encode to suit - thus “AUSTRALIA 2003” = 66,35,3,129,67,66,68,2,66,0,61,253,253,29 ‘————————————————————————————————————————‘Copy & paste main program below to “08” editor via=> www.picaxe.orcon.net.nz/morse.bas ‘Still scope for “telemetry” or tweaking SLEEP/NAP, as only 105 bytes (of 128) used as is! Close-ups of the AXE033 LCD kit. Note how the flexible solder mask strip must first be peeled away before inserting the header pins. ‘————————————————————————————————————————- Two terminal program screen shots, BananaCom & HyperTerminal, during the demonstration serial program run. 80  Silicon Chip www.siliconchip.com.au Symbol Tone = 100 Symbol Quiet = 0 Symbol Dit_length = 7 Symbol Dah_length = 21 Symbol Wrd_Length = 43 Symbol Character = b0 Symbol Index1 = b6 Symbol Index2 = b2 Symbol Elements = b4 ‘sets the tone frequency ( range 20 -127 ) ‘set quiet tone ‘set length of a dot (7 milliseconds)- yields 10wpm ‘set length of a dash (21 mS = 3 dots long) ‘set space between words (43 mS = 2 dashes, 6 dots) ‘set register for ch. ‘loaded with number of chs. in message ‘counts the number of elements ‘set register for number of elements in ch. Start: sleep 5 if pin3 = 1 then Identify goto start ‘NB - good program spot to turn on ID, via sensor etc maybe? ‘5 sec low power delay(varies if no pullup R)-modify to suit ‘wait for high input on pin 3 to start message- 1 by default ‘if no input,loop to start. Identify: ‘routine to lookup ch.& put its value into the ch. register for Index1 = 0 to 27 ‘cycle through lookup for times = number of ch. in message lookup Index1,(3,2,68,2,164,227,130,0,0,164,4,2,100,0,0,0,0,1,0,0,0,0,1,0,0,0,0,1),Character ‘ This means (S I L I C O N C HI P dit dit dit etc gosub Morse ‘go to the ch. generation routine next ‘loop back to get next ch. and load it goto Start ‘return to start to wait for next input Morse: let Elements = Character & %00000111 if Elements = 0 then Word_sp ‘look at 3 LS digits and load into Elements register ‘% means binary Bang_Key: for Index2 = 1 to elements ‘loop through correct no. of times for number of elements if Character >= 128 then Dah ‘test MS digit of ch. If it is 1 goto the Dah sub routine goto Dit ‘if it is 0 goto the Dit sub routine Reenter: let Character = Character * 2 next gosub Char_sp return ‘do a left shift on all the bits in ch. ‘loop back to get the next element ‘go to sub routine to put in inter-ch. space ‘return to Identify routine to get next ch. to send Dit: sound 0,(Tone,Dit_Length) ‘sound tone for dit length sound 0,(Quiet,Dit_Length) ‘silence for dit length goto Reenter ‘return to look at next element of ch. Dah: sound 0,(Tone,Dah_Length) sound 0,(Quiet,Dit_Length) goto Reenter ‘sound tone for dah length ‘silence for dit length ‘return to look at next element of ch. Char_sp: sound 0,(Quiet,Dah_Length) return ‘send silence for dah length after ch.completely sent ‘return to get next character Word_sp: sound 0,(Quiet,wrd_length) return ‘send silence for break between words ‘return to get next ch. www.siliconchip.com.au August 2003  81 References and parts suppliers . . . (also refer to previous months articles) 1. Ultrabright (white) LEDs 5600mCd range ~A$3 – various suppliers: Jaycar www.jaycar.com.au Dick Smith Elect. www.dse.com.au Altronics www.altronics.com.au Oatley www.oatleyelectronics.com etc 2. Lux meter – Dick Smith DSE Q-1400 (~A$100) www.dse.com.au 3. Australian Picaxe agents, MicroZed, handle the AXE033 LCD kit & RTC ($44) as well as Picaxe chips www.picaxe.com.au 4. A superb example of a well documented Picaxe program can be seen at www.hippy.freeserve.co.uk/axe18mon.txt 5. Banana Comm Terminal Program (shareware ~160k) Download from www. picaxe.orconhosting.net.nz/bcom30.zip 6. StampPlot Lite Ver 1.7 Shareware (~1.6MB)- now handles 2400bps OK. Download www.selmaware.com 7. Author’s revamped site with many links & usual demo program down-loads www.picaxe.orconhosting.net.nz 3. Given the abundance of older discarded notebook PCs, it’s tempting to raid the broom cupboard, dust one off and push into service running a Terminal program. Numerous compact organisers, such as the HP-200LX and Sharp Wizard OZ/ZQ 700 range, also Screen shots during a program run of the Programming Editor’s F8 and F9 serial data “terminals”. 82  Silicon Chip TERMDEMO.BAS ‘For Aug.”SiChip” display article. Stan. SWAN => s.t.swan<at>massey.ac.nz Ver 1.0 19/6/03 ‘Picaxe serial output demo for PC VDU display via almost any datacomms terminal program ‘Many exist,espec.classic Windows HyperTerminalPE (~700k) via => www.hilgraeve.com Free! ‘Install it then run - properties - make session -”Connect- Direct to Com1" & 2400,8,N,1 ‘Consider cheap 90s laptops/organisers too -Compaq Aero/HP 200LX & Sharp Wizard 7xx etc ‘DOS (but Win friendly) Banana Comm (~170k) espec.clean,& MODE CO40 allows enlarged text ‘Also works on Rev.Ed AXE033 16x2 alphanum. LCD kit,but text wraps since smaller display ‘Easy 2 wire serial only,here via “08” I/O pin 2 then D9F pin 2 for PC COM1 + pin 5 gnd ‘Suggest using 2 PCs for this - one as normal programmer, & other just for serout display ‘Program(s) can be downloaded => www.picaxe.orconhosting.net.nz/termdemo.bas,& also /bcom30.zip ‘2 notebook setup pix (Toshiba editor/Aero display)=> www.picaxe.orconhosting.net.nz/termdemo.jpg ‘NB-when Editing + 2 wire serial lead to correct I/O pin- F8 gives “mini terminal” ‘Even “datalogging” possible (via “F9” under Editor V 3.0.3 ) or via StampPlot Lite 1.7 ! ‘—————————————————————————————————————— demo: ‘ ASCII control codes <32 are IBM style serout 2,n2400,(12,10) ‘ Form Feed (FF)=clear screen- then a LF pause 50 ‘ brief pause before message shows serout 2,n2400,(“Hello from your PICAXE-08”) ‘ displays message in quotes serout 2,n2400,(32) ‘ acts on ASCII directly - a space pause 500 ‘ 1/2 sec pause for visual effect for b0= 65 to 90 ‘ / acts on direct ASCII request serout 2,n2400,(b0) ‘ so translates & displays next b0 ‘ \ A - Z characters in sequence pause 2000 ‘ 2 second delay to hold message b2=100 ‘ assign demo variable value b1=b2/2 ‘ simple divide 100 by 2 maths calc. serout 2,n2400,(32,#b2,”/2 = “,#b1) ‘ space,then calc.(# forces values) pause 1000 ‘ 1 sec. pause goto demo ‘ repeats entire message came with inbuilt terminal programs but these may not stoop to the Picaxe 2400bps limit. Programs found to give seamless displays were the classic but bland Windows “HyperTerminal”, a tiny DOS (but Windows friendly) “BananaComm”, and the astounding StampPlot Lite. This latter program not only shows normal messages, but handles comma separated value data (.csv – as used with Excel), with graphical display. Although initially written for the BASIC Stamp, StampPlot works with any serial data stream- the US author even kindly tweaked it for 2400bps Picaxe use! Compared with the AXE033 LCD, a full PC terminal program like Banana-Com allows both a wider screen and larger text ( via MODE CO40 ), ASCII control codes ( such as CR/LF ) plus saving and printing etc. With a small computer like the 1993 Compaq Aero used here, this approach may be a versatile “zero cost” display solution. The TERMDEMO.BAS demonstration serial data Picaxe program needs no external hardware beside the serial output cable. It simply displays a repeating message to whatever terminal program (or LCD) you’ve connected via the 2 wire lead. Note how # forces actual result variables (rather than just messages) to also be displayed too. You’ll no doubt quickly tire of irksome cable swapping when exploring display syntax effects, so it’s (again) suggested that two (notebook?) PCs be used – one for editing, and the other as a display terminal. Good viewing! SC www.siliconchip.com.au