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Help me out?

Discussion in 'Microcontrollers' started by Maarten, Oct 20, 2017.

  1. Maarten

    Maarten New Member

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    Hey guys,

    So I am here again to seek help... But I guess it's the right place to be.

    I found a project that i wanted to make. I'll explain it a little so that you guys will understand my questions,,
    It's actually a simple circuits, wich is a decoder of a DTMF signal ( IC: MT8870 ). The circuit has only one output, like a garage or light or w/e that's not the problem. And it only works when you call a specific numbers and then code like on the tones 159.

    The circuits does work, but I can't use it because they used after the DTMF IC a microcontroller that I don't have. ( which I guess makes the 159 thing work ). The Microcontroller used is AT89C2051. And there comes a HEX code with it i think. Writes in nubmers and letters.. 0-9 A-F.

    I am not very familiar with microcontrollers and did some research about it...

    The questions I have are as follows

    Do I must use this microcontollers or can I change it to any microcontollers? Or must it be in 8051 family? Or can I change it to like PIC? or any other microcontollers, which is easier for me to program and find? (keep in mind the main task of the microcontroller will be only to secure the code like it only opens when the programmed code is type in the dial numbers.
    ( When i searched about it I think I can change it, and the microcontrollers only differ like when you have some serious big codes to do? Only think doubting about why this guy but that microcontroller specific and not like a PIC? )

    I also want to change the Code that it gives which must be programmed on that IC. But after some searching, i found out that it will be very hard (or impossible to do that ) is it like this? it is in HEX numbers.
     
  2. alec_t

    alec_t Well-Known Member Most Helpful Member

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    What circuit? The MT8870 IC has four output pins.
    You can use any MCU you like with that IC, but you will need a good understanding of how the IC works (signals in or out, timing etc) to make best use of it and, of course, you will have to code the MCU.
     
  3. MikeMl

    MikeMl Well-Known Member Most Helpful Member

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    The MT8870 decoder just decodes a single DTMF digit at a time. If you want to detect a sequence of DTMF digits, you need to implement a Finite State Machine that advances state-to-state only if the "next" digit is part of the expected sequence. You can do this with flip-flops, or you can implement the state machine as a series of IF() statements in code in a microcontroller. If I were doing this today, I would use one of these...
     
    Last edited: Oct 20, 2017
  4. dave

    Dave New Member

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  5. dr pepper

    dr pepper Well-Known Member Most Helpful Member

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    If you are new to microcontrollers look up arduino, its aimed at beginners but can also do more complex projects.
    The 8870 has a 4 bit output and a strobe output which goes active when there is a valid input tone.
     
  6. Maarten

    Maarten New Member

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    Thanks guys for your reactions. The day I typed it i was a little bit confused.... The day after it I did find a little bit more about some things..
    But ofcourse there are some points I still didn't find out.

    ( As i said before the main part of the circuit is just about the DMTF recieving a signal, and the microcontroller just accepts a specific signal. Like if you press 10 on the phone the lamp goes on.. )

    Firstly I wanted to ask about the microcontrollers AT89C2051.
    Do you guys have any idea why the maker of that circuits used this microcontroller? Does it have anything special for this circuit ( dtmf one ) ?
    When i looked on how to program that microcontroller google came up with very pricy stuff ? Is there a cheap and easy way for it and works?
    Can we uncode the HEX file I have for the microcontroller? Because I wonder what he used in his program.
    The important thing I did actually think about are these = Price and Size... The size of this one is very good..

    Yeah I meant the microcontroller, it has one output, actually maybe two or three. Also LEDs included for if it's working etc..
    I have tried to research a lot about it. And I am still looking for it. Do you advise me any sites ?

    Yeah that is like exactly what I was thinking about. But I guess the DTMF I don't need a module for that I can make it myself..
    The outputs of the 8870 can we connect to any microcontroller right? The outputs of the 8870 are they like ore high or low? If so it shouldn't be to hard to program a microcontroller to go on after the output pin 1 and 3 went high...

    I don't think i need to the digit at the same time.. Like one single digit at a time first like 1 then 2.. I guess it just takes a little longer?
    Hmm why did you specific that one out? Like are there specific things to keep in mind when working with a dtmf? Or is it just because you like working with that?
     
  7. MikeMl

    MikeMl Well-Known Member Most Helpful Member

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    I assumed you want to use a sequence like 354 to turn something on, and then 265 to turn it off. That implies that 353 or 355 would be ignored...
     
  8. dr pepper

    dr pepper Well-Known Member Most Helpful Member

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    The only thing you need to be concerned about is voltage, the 8870 is 5v so you need either a 5v micro or a 3.3v micro with 5v tolerant inputs.
     
  9. Little Ghostman

    Little Ghostman Well-Known Member Most Helpful Member

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    The reason they used the micro they did was simple, its likely to be the one the developer had most experience with. The point about one state then the next you kind of missed.

    It has to be one at a time, because the phone does a single tone at a time. ANY micro can be used and Arduino is good for the beginner (cant believe I now say that!!), Raspberry pi I wouldnt use for this. Having any code you8 want is easy enough. Infact you could have a master code that allows you to change the main codes over the phone.
     
  10. Maarten

    Maarten New Member

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    Yes that is what I am talking about.. I will press one the dial like 354 it goes on, when i press 265 it goes off.

    Thanks, i must keep that in mind yes.

    That sounds fairly too me, that might be the reason yes.
    Like if I found any other type of the 8051 it should work fine as well, right?

    There is just one thing between the 8051 and the Arduino ... And this is the price.

    The arduino mini clone is like 4 times expensiver than that 8051 I mentoined... ( this is as far as I know? Maybe the Arduino can be found cheaper if so tell me? )
     
  11. be80be

    be80be Well-Known Member

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