http://www.8051projects.net/ Learn to make simple microcontroller projects, pic, 8051, avr and arm projects. download 8051 projects, tutorials, libraries, sample codes. join the microcontroller discussion forum and ask doubts regarding electronics. the best source for 8051 over internet. en-gb 2008-11-20T22:59:29-08:00 contact@nospam.com hourly 1 2000-01-01T12:00+00:00 http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 hello everyone,i recently finished my first project (car based on 8052 uC with wired remote).now i want to make remote wireless and i am thinking about dtmf (not rf). i read about it on net (googled it and read many tuts), but don't get anything !!! i dont know about circuits much !!! so please help me !!!i also found a good site but not get much !!!http://www.freewebs.com/maheshwankhede/dtmfdecoder.htmli donot konw how to interface phone with these chips( CM8870 and KT3170) and the circuit diagram is very diffcult to understand !!! i dont know what to do ??? http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 rahuljin i want to use a nokia mobile phone (1100) !!! but dont know how to connect it with the circuit (receiver side) !!!i hav to put all the resistors, capacitors and transistor or they are in build ???my plane is to call the other phone on car through my phone !!! and then operate the car with my phone !! http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 Ajay Please tell me what problem you are facing..the circuit given in that website is fairly simple. i recommend you to read datasheet of CM8870 will make you clear about the working of IC and interface.DTMF also need a wired interface.. are you going to use telephone line? http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 Ajay oww.. ok.. thats a good idea..yes you need all resistor caps and crystals..also you need to make circuit that detect ring and pick the call.. after that directly couple the speaker with CM8870. http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 rahuljin so i ahv to open the mobile phone and do the circuit work ??? http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 Ajay no.. make use of headset.. just use the speaker wire.. be smart http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 xx1mar I think you are planning to interface your nokia phone with the microcontroller and control it by dtmf. you can use the CM8870 as your dtmf receiver. it is very easy to build.. you can use winbond w91312 as your dtmf tranmitter http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 Ajay there is no need to transmit DTMF as there nothing on the user side which can understand DTMF. and ofcourse CM8870 is the best choice for DTMF conversion/reception. http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 rahuljin hi can u tell me what is the relay dpot in that circuit and what is the use of that circuit ,and also how can i connect the whole circuit with the headset of the phone as u have mentioned above do i have to cut the wire of headset and then join it to circuit http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 rahuljin hello !!! any help http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 Ajay sorry rahul.. i missed your thread, its not DPOT relay.. its DPDT (dual pole double throw) Relay. Its a type of relay. yes you need to take speaker off by cutting wire. http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 rahuljin thanks for the reply !!!i dont get the use of this DPDT reply !!!so what is the need of ring detector, i mean nokia has a option to accept the call automatically !!also i want to ask that the wires are attached to relay or can i attach them to dtmf decoder ??? http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 Ajay as perl the link you posted in your first post, that person uses telephone line not a mobile phone. so you can remove relay and directly connect the mobile to MT8870. http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 rahuljin can u tell me the use of this relay ??? http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 Ajay relay picks up the phone.. when ring is detected.. microcontroller switch on the relay and hence phone is answered. http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 rahuljin so even without relay i hav to use ring detector circuit or not ??? http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 Ajay Well usually there is facility in every mobile for auto answer, if you enable it.. then you need to decide how to detect if call is activated or not..One thing you can do is.. use auto answer and ask user to press * to start with the further work.. you can also couple microphone with controller to feed voice response.. http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 rahuljin i have done everything !!! but i am facing a problem.i sent the dtmf tone to other mobile then it is taken by cm8870 and output of cm8870 is obtained. then this output is given to microcontroller, and an other output is obtained at other port of microcontroller. now my problem is that the port does not refresh after the output is obtained. i get same output untill i press another key !!!i tried to give setb to std (in cm8870) through microcontroller !!i also tried to refresh the port but no use !!! http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 GioppY You have to wait the end of the dtmf tone; check the stb pin.Something like this pseudocodeCODE:Sub St_dtmf
         if Stb = 1 then
            mov     a,P0               ;get data from MT8870
            anl     a,#15               ;4 bit  low nibble
            lcall   conv_tone         ;convert to ascii
            Txx  =  Acc
            DtmfString = DtmfString + chr(Txx)         ;save
            do
            loop until Stb = 0          ;wait end dtmf
         endif
End sub
;
Conv_tone:
        inc     a              
        movc    a,@a+pc        ;get from table
        ret
        db      H44,H31,H32,H33          ;D123
        db      H34,H35,H36,H37          ;4567
        db      H38,H39,H30,H2A          ;890*
        db      H23,H41,H42,H43          ;#ABC
 RegardsGianni http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 amer in telephone line interface the input lines to DTMF is speaker lines or what? http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 rahuljin sorry, but i used a mobile phone due to which the circuit not only becomes very simple but the application of this project is also increased. the speaker(which is kept near the ear) wire is connected to dtmf decoder. http://www.8051projects.net/forum-t4286.html 2008-11-20T22:59:29-08:00 ۞ TPS ۞ please go through this linkhttp://onlinetps.com/raghu/