Advice needed on multiple analog inputs to PC
Joshua Siegel
Posts: 51
Hi everybody,
I just bought a large quantity of analog sensors for a robotics project. They output from 0-2.54V in 10mV incriments. I also have some 5V sensors that I'd like to use on the same board.
The total number of inputs is 21 (though I can make it work with 20). The resolution needed isn't that great, maybe 8-bit? Even that could be overkill. The max expected refresh rate is 50-60Hz.
I'd love a USB interface, but serial works too.
What can I buy for a reasonable price that can handle 20-24 analog inputs at 60Hz and interface easily with a PC? I've considered stamps, but they all have 8 analog lines max, and some don't seem to enjoy reading voltages.
I'm currently using Phidgets interface kits, but would like to minimize my hardware (I'd need three $90 boards due to the 8 input limit).
Thanks for the input (what a bad pun - but it was necesary!)
Josh
I just bought a large quantity of analog sensors for a robotics project. They output from 0-2.54V in 10mV incriments. I also have some 5V sensors that I'd like to use on the same board.
The total number of inputs is 21 (though I can make it work with 20). The resolution needed isn't that great, maybe 8-bit? Even that could be overkill. The max expected refresh rate is 50-60Hz.
I'd love a USB interface, but serial works too.
What can I buy for a reasonable price that can handle 20-24 analog inputs at 60Hz and interface easily with a PC? I've considered stamps, but they all have 8 analog lines max, and some don't seem to enjoy reading voltages.
I'm currently using Phidgets interface kits, but would like to minimize my hardware (I'd need three $90 boards due to the 8 input limit).
Thanks for the input (what a bad pun - but it was necesary!)
Josh
Comments
If you are a "mimimalist" kind of guy, you can do all this with a single SX48 chip plus two resistors and one small capacitor per channel. The (Virtual) A/D converters function mostly in software, and that chip will easily handle the speed and the resolution you specified.
Communication with a PC is also readily handled by the same chip, again, mostly in software as a Virtual UART.
The chip has 36 I/O pins, and 2 are needed for the comms, leaving the rest (34) for analog channels. Perhaps a couple of LEDs, so 32 analogs is good.
Total cost for the "channels" 32 times 5 cents..... about a buck and a half!! The SX48, power supply, RS232 etc is on top of that of course.
Sounds like a good candidate for one of the Parallax project boards...... around 10 bucks if I recall?
I'll help you if you're interested...... should be a hoot!
Cheers,
Peter (pjv)
I'd have 12 pwm lines and 8 analog in (from my IR). I'd still like to be able to read simultaneously instead of sequentially, or at the very least, update around 50-75Hz. I would be firing all the sensors simultaneously from a digital out to their trigger pins in order to avoid interference.
This way, I could also impliment a compass module and have that fed over serial to avoid needing a specific board for that.
Thoughts?
Thanks!
edit: I'd still need one more input for my potentiometer... Would one of the 40 pin stamps work? What type of board/etc would I need to buy (assume I have nothing).
Serial cable, chip, board...
www.maxim-ic.com/products/i2c/
And this Phillips (the people who invented I2C) I2C brochure. First items covered are ADCs:
www.semiconductors.philips.com/acrobat_download/various/philips_i2c_handbook.pdf
You should find their PCF8591 of particular interest. It is available at DigiKey, P/N 568-1087-5-ND, $3.49 each/singles. 8-bits, 4-multiplexing channels in single-ended mode, two in differential. This also includes an 8-bit DAC! Very ooh-ooh-ahh-ahh! The data sheet is at:
www.semiconductors.philips.com/acrobat_download/datasheets/PCF8591_6.pdf
All you have to do now is implement this simple serial protocol in the SX. Doesn't SX/B have I2C yet?
Hope this helps!
kenjj
Since it has 8 processors in parallel, it might be a better sensor management concept. There are 32 I/O pins, so it would only achieve 30ADC lines without ADC chips when leaving two pins for communications to the outside.
Pjv,· how does one get one channel per pin on the SX-48 and/or the Propeller.· My impression was that the 2 pins were dedicated to one ADC.· Your count seems to imply another scheme is available.
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Post Edited (Kramer) : 7/9/2006 3:32:46 PM GMT
Josh, I give up!
You pose a question/problem, and are given a totally applicable solution, then you change your needs so that the solution requires a slightly different answer. Now I don't know what you really ARE looking for! The Maxbotix sonar provides all three, analog, PWM and serial output, and your I/R, I don't know. So if you want to use something different, drop some of the 32 analogs I suggested.
All analog readings would very nearly be at the same time.
I just can't understand why anyone would opt for a more expensive and more complicated solution by using external A/Ds.
The virtual A/D software really IS simpler than any communication to external devices, and the price per channel is 5 cents.
To boot, you can choose the resolution you want, anywhere from 2 to 12 bits (all the same 5 cents); in some cases I have even managed 14 bits, but now the layout becomes important (as it would with any 14 and up bit A/D).
And using one I/O pin pin over 2 pins per channel only degrades the performance slightly. For 8 to 10 bits?, No Problem.
As I don't have a BOE, nor own any STAMP, I have no idea as to their capability. All you would need is a Parallax SX48 proto board for $10, and an SX-Key. You could write your application in SX/B, and because the A/D software is very time critical, I'd be happy to write the assembly virtual A/D program to mesh with that.
Kramer: The typical way for virtual A/D with an SX is 2 port pins. For lower speed applications (say up to 100 samples/sec) you can get away with 1 port pin per A/D with a slight degradation in performance; I have not measured it, but I expect 0.1% to 0.5%.
Cheers,
Peter (pjv)
If you would be so kind as to refer me to a schematic for the 'one pin' ADC, it would be quite helpful.
I just abandoned a project because I thought I didn't have enough I/O pins for the ADC. The resolution is quite minimal and I DO UNDERSTAND that both the amount of programing and the cost are very small.
I looked into an 8X ADC and it is just plain hell to program via synchonous serial. It takes a huge space in your EEPROM, requires more RAM buffers, and will occupy your mind for a week or so.
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Be happy to.
Since I don't have a drawing/schematic package at home, I'll try to use the new Propeller character set to create it. I believe that means you need to install that too in order to display it.
I'll experiment with that, so please be patient through my trials.
Cheers,
Peter (pjv)
Peter - I really didn't mean to step on toes or disregard your earlier suggestion, so I apologize if I came off as blowing you off. I just realized that I was offered other forms of output from the sensor, and that it might make it simpler to interface in the long run, especially since I've used stamps before, but never the Parallax SX series. I really do sincerely appreciate all the help I can get, and the last thing I want to do is make people question why they should be offering me advice.
If your offer still stands, I'd be willing to place the order early tomorrow. I'd just need to know what hardware to get, as far as resistors and capacitors. I'd also like it if you would make sure I order the right stuff from Parallax for an SX-newbie to get set up properly.
If I understand correctly, I'd be ordering:
SX tech kit (comes with SX-key, serial cable, tech board) and a protoboard (or two) which would be about $100.
or, I could be a bit cheaper and order
SX-Blitz + cable + protoboard = $60. Is the kit worth the price difference? I'm on a tight budget to stay within the confines of my grant, but I dont want to buy something only to replace it a month later when I fall in love with this chip (Parallax has a way with me [noparse]:)[/noparse]). I'm sure I could use the tech board for other projects, and I think I've just answered my own question...
Either would need a power supply - can I use a 7.2V battery for it?
Thanks again,
Josh
edit:
I guess the final verdict is that I'd be using
12 2.54V sensors in 10mV incriments
8 5V infrared sensors in about the same - previously, I had been using 12 bits of resolution, but anything over 8 should be reasonable.
1 5V potentiometer
now I just need to find out how to use a compass over serial, i guess - though this can come at a later date
Post Edited (Joshua Siegel) : 7/9/2006 11:36:39 PM GMT
First and foremost, I was not offended, just a little frustrated.
Secondly, the ONLY programmer to buy is the SX-Key. The Blitz is fine for programming ONLY; it won't let you debug and single step through your program. I'm 100% sure this is something you will want (and need) to do.
Which kit you purchase is up to you, as long as it contains an SX-Key. My reccommendation for convenience would be the SX Tech board (SX28) for easy prototyping, and the SX Proto board (SX48) for your final project.
The SX48 proto board will be a perfect starting point, and only 10 bucks.
Resistors and capacitors I'll advise you on later..... some are not critical.
Buy a 9 or so volt "wall wart", center pin positive, if that is not included in the kit.
Could you please specify the output impedance of the other (non Maxbotix) analogs. Or if you don't know tell us what they are, and we can find it or make an educated guess.
We'll have a blast!
Cheers,
Peter (pjv)
The other sensors are the Sharp analog sensors. I have the datasheet here somewhere, so I'll see if I can find out what the output impedance is.
Actually, here it is:
http://www.junun.org/MarkIII/datasheets/GP2Y0A02YK.pdf
I don't see it in there. Does it go by another name?
Yup, a pretty incomplete set of specifications..... but we'll take a stab.
What do you have in the way of test equipment: oscilloscope, digital volt meter, selection of electronic components, resistors, capacitors, transistors, that kind of thing?
I want you to learn through this process, so I'll be pointing you in the right direction, and let you discover the wonderful world of SX with only as much guidance as you need. So, I'll be asking you to make some measurements on the IR unit.
Also, just so we don't embarrass each other, how experienced are you in electronics and microprocessor programming?
Cheers,
Peter (pjv)
I always appreciate learning rather than simply being given a solution [noparse]:)[/noparse].
I have a multimeter, some components laying about (though most are in projects now), and I just bought a 2 channel Tektronix oscilliscope from a local junk haven (the price was right and I couldn't resist). It needs probes, but I can order some later this week from MPJA or some other surplus house.
As for experience, I understand circuits and logic well. I've done plenty of "basic" projects from 555 timer circuits operating relays to H-bridges to various other function generators, etc. I can read schematics and diagram circuits (but not PCB's), and I've even touched on SMD (but can't say I did well with it). My experience level is probably on a par with what most high school students would have after a course or two in electronics, though I've honestly never taken a real "course" myself.
My microprocessor experience is null - I've worked with high level chips in basic, java, and C, but never down to assembly code. I'm always willing to learn, though.
What's the first thing I should do? I've been reading through a bit of "Programming the SX Microcontroller," but some code ideas or schematics would help.
I guess what I'd like the final 'product' to do is output (serially) a string of the values from each input, perhaps
XXXAXXBXXXXC
with A as sensor 1, B as sensor 2, and so on - unless you can suggest a better output method. This seems by far the easiest to parse in Java on the computer, making the sensors usable by many different languages.
It would also be nice to use the SX to trigger the sonar pulses, and it seems like this is a possibility. I'd just use one of the pins as an output, right? Set it high once per loop and trigger the readings?
Good, I'm ready to guide you in your quest for knowledge..... I'll point you in what I think is the right direction, and help only as little as you need, so that you can discover as much as possible on your own. That way you will retain the information much better.
As a stater, please read the App notes on the Parallax website pertaining to (virtual) A to Ds.
Then the next thing we will do is build a software D/A converter; this is the basis of making an A/D converter.
So you will need 2 resistors of the same value (ony one for the D/A, but the second resistor when we implement the A/D) of 10,000 Ohms, and a small capacitor of 0.01 uF. The restor values are not critical per-se, but do need to be of equal value, in fact as identical as possible, including temperature coefficients. So any two "out of the same batch" will be just fine. Thecapacitor value is also not critical.... it depends somewhat on the speed of the signal you are expecting to measure.
Please devour the App notes.
More later.
Cheers,
Peter (pjv)
I did, however, find this link on SX-list:
http://www.bytecraft.com/addaconv.html
Would this be the schematic for the circuit you're describing? One capacitor and two resistors per sensor. I've read it over several times and it makes a bit of sense, but as of now, I have no way to impliment it. Step by step would probably be best, I suppose, if you can point me to some more basic reading on the subject.
Thanks,
Josh
Time is very tight for me just now (wife's birthday), so I won't be able to do much until the weekend.
I have not looked at the SXList site, but it sounds like the right animal.
We'll start by making a "pulse density modulated" (just a special form of PWM) D/A converter as that is what is needed to make, and understand the A/D converter.
Please confirm that you bought an SXTech board and an SX-Key.
You will need to have the resistors/capacitor available to proceed with testing. Your oscilloscope will be VERY beneficial. Do you have the probes yet?
Cheers,
Peter (pjv)
I'll see if I can find and PDM/PWM sites and read what I can to get a feel for that.
I have the SXTech board, an SX-Key, the cable, power adapter, and the SX48 proto board for the final product. I've been thumbing through the books to see what I can figure out.
I'll grab some resistors and capacitors from R/S tomorrow, and maybe place an order from allelectronics to beef up my collection - what I though I had has been reduced to several LEDs and a few misc. components, but nothing that useful.
As for the scope, I have a probe but no trace yet. I've been troubleshooting for the past hour or so, and think it may be time to buy a manual [noparse];)[/noparse] - unless, of course, I bought a broken scope, which is a real possibility for the price I paid. I've gone through the millitary manual and the setup procedure from the normal operators manual with no trace. It triggers fine and the CRT lights, but even the 'beam find' button wont work. Two other people have suggested a shorted capacitor, but I have no clue what I should look for, and don't feel all that comfortable with HV circuits.
edit: found a copy of the service manual - its a Tektronix 7603
Josh
Post Edited (Joshua Siegel) : 7/21/2006 3:27:14 AM GMT
I'm sorry to be so tardy, but things just keep piling up on me; I have only a little time to dedicate to the forum just now.
I happen to see Bean's current post in the SX thread under the topic "SX/B v1.51 Questions", and his reference to the SX LIST, http://www.sxlist.com/techref/scenix/lib/io/adc_vp.htm, is exactly what you are looking for, and a better explanation than I would have time for to boot! The artice is written by Chip Gracey, no less, circa 1997.
I'm not going to abandon you, but this reference is probably all you need, at least for now. I know that you want to get the data into a PC; that should be a simple matter through a serial port.
Eventhough I'm really tied up, I still can sneak a quick peek at the forums every day, so I'll notice if you're hollerin'
Cheers,
Peter (pjv)
I haven't had much luck with converting their code, for the two line with interrupt, to a one IO pin setup. I'm learning a lot about SX/B and a little about assembly, though. My one question for this part would be, do I really need an output pin?
Right now, I guess my primary goal is to get some output that I can read in hyperterminal. Would a SEROUT be a suitable way to do something like that? I could perhaps concatinate a string, and send it out like that... Maybe something like this: http://forums.parallax.com/forums/default.aspx?f=7&m=109987&g=110003#m110003
Off to read about more of the commands!
edit: I've been trying Jon Williams Serout string examples, because this will be the best way for me to figure out if my ADC's are working... No luck yet, I'm assuming that's because its TTL levels and I need RS232, right?
Thanks!
Post Edited (Joshua Siegel) : 7/30/2006 11:21:45 PM GMT
Anyway,
I've spent the past several days continuing to read about this stuff and still haven't had much luck. It's getting quite frustrating and to the point where I just want to see SOME progress to know that my time has not been wasted.
Serial output was a mess, running Jon Williams code I got nothing but jargon. Tried different bit rates, inverted, not, blah blah blah (of course, starting with what has been tried and known to work, then I monkeyed with it in a futile effort to exact some response). My main feeling is that this is a TTL/RS232 issue, but haven't been able to verify. I've tried on two different computers and get different characters, so thats what leads me to believe that. I'm on the tech board right now, with a 50mHz resonator in place - the one that came with it. It is set to OHCS2, I believe, so that shouldn't be the problem. I've also tried the 4mHz.
After getting tired of playing with that, I wanted to see if there was any simple way I could see if the board was even reading, because I thought I might be able to start my input code. I was going to try the ADC schematic, but still do not know how to get the dual line (input/output) code to function with a single line (seemingly input only, or is that a fast switch?).
I tried the PWM out, rather than serial out, and tried to light up a LED to vary intensity with difference (pretty much a pulsin = pulsout deal). No luck there. Then I tried to get it to flash the number of inches away my hand was. Still no luck. I dont know if it isn't reading or what, but can't really tell until I can do a serial out. It could be anything from improper conversion to simply not having a solid enough power supply; I'm running my sensor(s) off of the Vdd/Vss on the board, and though they're within spec, I feel like maybe its too much draw.
Thoughts, anyone?
PJV?
I just need some direction at this point... I'm kind of burnt out from trying to teach myself SX/B and the related assembly, and would like to have something to show for my days of effort.
Thanks!
Josh
edit: Ordered the parts to make a TTL/RS232 level shifter (bidirectional). I never knew that it was a 0-5V scale on TTL, I thought it was +/-5 like rs232's +/-12. I guess that explains why, even with intentional "slop" in design, it had no semblance of proper output... But that still doesn't explain why it works for some people without a shifter?
Post Edited (Joshua Siegel) : 8/3/2006 2:39:57 PM GMT
I really understand what you are going through. In the beginning there is a huge blur between what is hardware and software.
You are on the right track to get the HARDWARE verified first. Try the simplest of things to do. Then move to the software.
Regarding RS-232......
One of the biggest RS-232 problems is laptops. They often are so non-standard that they won't work well with other devices.
The MAX232 chip is the usual quick fix and it converts TTL into a good +9/-9 RS-232 and does the inversion from a +5v supply.
Of course, you can use transistors to make a similar level shifter. 2n3904 and 2n3906 transistors will do fine. They will invert, but the signals [noparse][[/noparse]without a +12 and -12 supply] will be +5 and 0 inverted from the TTL.
This may quite often be what the laptops are doing. And yet, True RS-232 provides that negative voltage which is being omitted.
'Trying on different computers and getting different characters'
A. It could be that Hyperterminal [noparse][[/noparse]or whatever] is set to different values - baud rate, 7 or 8 bit, stop bits, parity
B. It could be that software is in one instance set to invert the input and in the other to not do so.
C. These days it is possible to have ANSI characters versus UNICODE. Generally, the 0-9 and A-Z will be the same in both. But other characters may be presented visually quite different. There is a FREEWARE called Terminal that will give you consitent display in Hexidecimal and much greater clarity about configuration via trial and error. Try this link http//:bray.velenje.cx/avr/terminal/
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I should have my RS232 converter soon, and that should help out. Its a MAX232 adapter from acroname, which I've previously used with their BrainStem (though the device didn't belong to me and I dont have access to it anymore).
I'm using desktops for both terminal windows, because my laptop has a serial adapter and I didn't want to throw in another can of worms to the mix. The settings on both machines were the same, 9600 baud, inverted, 8 bits, no parity, no flow control. I imagine that the differing characters were, as you suggested, either the result of a different character set or the computing mayhem that occurs when a TTL device is connected directly to a rs232 port. I'll try again later today, but I think I might take a break from the serial output portion until I get my adapter.
I'll try out that software later today, and then probably just wait patiently for my package to arrive from Colorado until I try any more. In the meantime, I can busy myself with looking at compasses (I've been looking at the Dinsmore 1525 lately).
Thanks again!
Josh
Sorry, I've been terribly busy getting a project finished of.... about 4 months solid now.
I will suggest we start with making a D/A converter with one of those pulse density modulated R/C integrators.
Hopefully your scope is running as it will be a great help in seeing what is going on.
Please make sure you have a small capacitor (o.1 uF) and a resistor, any value 1K to 10K is fine. Later you will also want two 10K and two 100K resistors and possibly a 0.01uF capacitor.
Please read up on interrupts as that is critical in the D/A, A/D and communication code.
Preferably I would rather not just hand you the code; I think you will learn more if I just guide you in developing it yourself. That will be a slower process.
I guess to get rid of some of those frustrations some small success celebrations will help...... you decide. We'll have you up and running quickly, I'm sure.
Cheers,
Peter (pjv)
I don't know if you saw it, but SX/B 1.51 has a new command that does EXACTLY what you want. It's called ANALOGIN and it uses the PDM (continuous calibration, bitstream, whatever) method to read an analog voltage.
Because it doesn't use interrupts the circuit must be "primed". This is done by running through the loop 256 times before actually starting to measure/count stuff. You can make the priming stage longer too (in case you have a bigger cap or larger resistor values).
Here is a link to SX/B 1.51 in case you don't have it·http://forums.parallax.com/showthread.php?p=597707
Bean.
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·
the scope is still a no-go, but I'm going to try and troubleshoot the power supply this weekend. I keep reading about dead capacitors causing this problem, but its never a specific number, so it's hard to pinpoint.
PJV, I understand completely the desire to teach rather than hand me the code, and I appreciate your motive and know I personally want to LEARN rather than have something handed to me. I have all of the components handy, from batches of resistors (picked up about 1,000 bulk) to capacitors, and will start wiring as soon as I can.
That said, the ANALOGIN feature seems to be exactly what I need. I'm going to fool around with that, but still want to learn how and why it works. I feel like I have a good, basic understanding of the concept but the little details are what throw me off. Perhaps seeing it in action will be a little impetus for me to make that final mental click?
I'll try my hand at running one or two of these sonars and getting a reading back. My only concern at this point is that, without being able to see the value returned from the sensor, I wont have a usable way to tell if my output is, well, usable. I can't very well convert an unknown value to a certain number of LED flashes without getting a ballpark to start.
I'll take a look at SX/B 1.51 and read up on the commands. I've already digested all I can of PDM, PWM, Delta-Sigma modulation, and virtual ADC's. There's a printout as big as a Caddilac sitting on my desk right now [noparse]:)[/noparse].
Josh
I must have a look at what code that instruction generates...... but immediately I have a concern:
It is not possible to do software A/D conversion without executing the DAC at exactly the same time in a loop, hence the requirement for interrupt. Any code that causes the DAC to waver in its timing will throw the reading off. The amount of error will depend on the amount of timing inconsistency.
Again, I have not looked at the code, so if you are some how tricking things for timing to be consistent then it will probably work. Also it would work if you stall everyting else while you are taking a single reading, and that seems pretty impractical to me, especially if you need to communicate serially at the same time.
Where I am going with Josh is simultaneous communications and A/D conversions. The conversions are done "out of sight" in a precisely timed interrupt routine, as are the communications.
I'll try to look at your compiled code tonight.
Comments??
Cheers,
Peter (pjv)
70 000B 0CFA MOV FSR,#__TRISA ; ANALOGIN InPin, OutPin, value 000C 0024 71 000D 005F MODE $0F ; Set InPIn as Input 72 000E 0500 SETB IND.0 73 000F 0200 MOV !RA,IND 0010 0005 74 0011 0018 BANK $00 75 0012 0CFA MOV FSR,#__TRISA 0013 0024 76 0014 005F MODE $0F ; Set OutPin as Output 77 0015 0420 CLRB IND.1 78 0016 0200 MOV !RA,IND 0017 0005 79 0018 0018 BANK $00 80 0019 0C02 MOV __PARAM3,#(1+1) ; Times to do the 255 count loop 001A 002A 81 001B 0CFF MOV __PARAM2,#255 ; Count 255 loops 001C 0029 82 001D 0068 CLR __PARAM1 ; Clear counter (value) 83 001E 0705 JNB InPin,$+7 ; Is input low ? Jump to (88) 001F 0A25 84 0020 0000 NOP ; Waste time 85 0021 02A8 INC __PARAM1 ; Adjust count (value) 86 0022 0425 CLRB OutPin ; Make output pin low 87 0023 0010 JMP @$+7 ; Jump to (93) 0024 0A2A 88 0025 0525 SETB OutPin ; Make output pin high 89 0026 0000 NOP ; Waste alot of time 90 0027 0000 NOP 91 0028 0000 NOP 92 0029 0000 NOP 93 002A 02E9 DJNZ __PARAM2,$-12 ; Inter loop (255) 002B 0A1E 94 002C 02EA DJNZ __PARAM3,$-17 ; Outer loop (prime+1) 002D 0A1B 95 002E 0208 MOV value,__PARAM1 ; Save count (value) 002F 002DBean.
[noparse][[/noparse]edit] I see I forgot the [url=mailto:'@']'@'[/url] for some of the jumps. I'll have to fix that... That will change the timing too... Darn...
81 000E 0CFA MOV FSR,#__TRISA ; ANALOGIN InPin, OutPin, value 000F 0024 82 0010 005F MODE $0F ; Set InPin as INPUT 83 0011 0500 SETB IND.0 84 0012 0200 MOV !RA,IND 0013 0005 85 0014 0018 BANK $00 86 0015 0CFA MOV FSR,#__TRISA 0016 0024 87 0017 005F MODE $0F ; Set OutPin as OUTPUT 88 0018 0420 CLRB IND.1 89 0019 0200 MOV !RA,IND 001A 0005 90 001B 0018 BANK $00 91 001C 0C02 MOV __PARAM3,#(1+1) ; # of time to do 255 loop 001D 002A 92 001E 0CFF MOV __PARAM2,#255 ; Setup for 255 loop 001F 0029 93 0020 0068 CLR __PARAM1 ; Clear counter (value) 94 0021 0705 JNB InPin,@$+14 ; If pin is low jump to (101) 0022 0010 0A2F 95 0024 0000 NOP ; Waste time 96 0025 02A8 INC __PARAM1 ; Adjust value counter 97 0026 0425 CLRB OutPin ; Make output low 98 0027 02E9 DJNZ __PARAM2,@$-6 ; Loop 255 times (94) 0028 0010 0A21 99 002A 02EA DJNZ __PARAM3,@$-12 ; Loop until done (92) 002B 0010 0A1E 100 002D 0010 JMP @$+9 ; Jump to done (104) 002E 0A36 101 002F 0525 SETB OutPin ; Make output high 102 0030 02E9 DJNZ __PARAM2,@$-15 ; Loop 255 times (94) 0031 0010 0A21 103 0033 02EA DJNZ __PARAM3,@$-21 ; Loop until done (92) 0034 0010 0A1E 104 0036 0208 MOV value,__PARAM1 ; Save value in variable 0037 002DOkay I put the [url=mailto:'@']'@'[/url] in the jumps AND make the loop tighter. This will be in the NEXT release. (1.51.01 ?)
Bean.
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Post Edited (Bean (Hitt Consulting)) : 8/3/2006 7:18:13 PM GMT
I still have not had a chance to detail your code, but a quick observation indicates that you balance the times by stalling for the right duration.
I believe this procedure will not permit multiple simultaneaous readings, nor simultaneous communications??
What I have for Josh is an approach that permits both.
Josh, I spent quite a bit of time this weekend trying to get a sketch from "paint" to a reply in the forum, but no luck.
I'm rather PC "challenged"!
If you (or anyone, please) can help me with that, then I can move on. Also I had difficulty in exporting the "Spin" graphics characters (graphic characters change to small squares), but might yet figure how to get that to work. I believe you would need to install the Parallax font in order to be able to see it. Perhaps you have already done that. Please let me know if that is a reasonable avenue for you.
Anyhow, I'm hoping to wrap my project up in the next week, then I will be more available.
Cheers,
Peter (pjv)