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How to read an LCD display with a microcontroller?

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Unread postAuthor: ramses » Tue Oct 06, 2009 2:52 pm

Interesting. I've also heard of something that pulses the laser at several frequencies with something like a sine wave, detects the strength of the reflection, and finds where all of the sine waves intersect. That is even less practical. The main reason I don't want to build my own range finder is that I can't figure out how to 1. accurately measure the time, and 2. detect the doubtlessly tiny pulse created from the reflected laser, while filtering outside "noise" (changing light based on leaf movement, etc.). The second is easily remedied by carrying a large pulsed Q-switched laser, but that is unsuitable for my purposes and still leaves the second issue.

Creating my own rangefinder would most likely knock $100 of my budget (which currently stands at around $200) I would still be over budget, but not by nearly as much.
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Unread postAuthor: POLAND_SPUD » Tue Oct 06, 2009 4:25 pm

so do you need a range finder to increase accuracy or rather to set a sort of time delay of a fuze ? (non explosive of course... I think you've mentioned that project earlier)

if you need it for accuracy only then you could get away without reading the LCD with a micro-controller...
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Unread postAuthor: ramses » Tue Oct 06, 2009 4:36 pm

Who said this had anything to do with spudguns? and It wasn't my idea to set a delay "fuse" with a rangefinder/microcontroller.

Sorry if that came out harsh, but whatever.

From what I understand:
If the output to the LCD is digital, read that via a digital pin on the microcontroller. Any idea how to do this with arduino?

If the output to the lcd is analog and the digitization takes place on that board, read the analog voltage at one of the analog pins on the arduino. this seems straightforward, assuming the max voltage is 5 and min is 0. That would give me something like 10 bits of resolution, and accuracy to the foot (accuracy not precision) For clarification, there are 1024 possible readings between 0v and 5v. therefore, a reading every .004... volts. YAY!

I still have no idea how to deal with the circuit if the processing happens all in one chip, with no access to a data line of any type. Perhaps someone could suggest a solution.
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Unread postAuthor: jimmy101 » Wed Oct 07, 2009 10:45 am

ramses wrote:If the output to the LCD is digital, read that via a digital pin on the microcontroller. Any idea how to do this with arduino?

If you get lucky and the data is transfered serially between the range finder and the display then you should be able to read that with the Arduino's serial IO capabilities. It may be possible to do that with just two connections between the range finder and the Arduino. (I'm sure there's a library and/or examples somewhere of reading RS-232 type data with that chip.)

Have you done a web search to see if anyone has already hacked your particular range finder?
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Unread postAuthor: TurboSuper » Wed Oct 07, 2009 3:10 pm

Mmm...if there is a serial interface it could very well not be asynchronous. You could just capture serial data by polling one of the pins, transfer it to a PC, and then view it in excel (use the sampling rate as your time base) to get an idea of what you're looking at.

Either way, there's no "5 minute solution". It will take a healthy bit of analysis.

Have a look at this program, it lets you use your PC's parallel port as a logic analyzer:

http://www.trikaliotis.net/pposc
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Unread postAuthor: ramses » Wed Oct 07, 2009 4:53 pm

No, specifics, although a patent specifically mentioned it as a candidate for hacking. I suppose I will have to invest in one to experiment with. I hate spending $100 on something that I might brick and be completely unable to fix, but it looks like I have no other choice.

actually, I found this. Possibly more trouble than its worth, and thisA 40MHZ could be workable.

not too bad, but the convenience of the manufactured product might outweigh the cost benefit of a homebrew system, particularly because of the pre-aligned viewfinder, which will be convenient to align with other optical systems.

TurboSuper wrote:Mmm...if there is a serial interface it could very well not be asynchronous. You could just capture serial data by polling one of the pins, transfer it to a PC, and then view it in excel (use the sampling rate as your time base) to get an idea of what you're looking at.
that would be fine for development, but it would be easier to hook up a 10 seg. keypad to the microcontroller and manually enter the numbers for field use (which is unacceptable, BTW. Otherwise, the question wouldn't have been asked)
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Unread postAuthor: TurboSuper » Wed Oct 07, 2009 9:06 pm

I meant to use that method to figure out what serial protocol was being used (if any at all). Then you could configure the Arduino appropriately. Obviously you wouldn't lug a PC around with you :P
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