24th July 2010 04:40 AM
DTMF reciver for mobile
its my 2nd thread i hope my problem is solve
i want dtmf reciver for nokia mobile
dtmf reciver easily interfarnce with mobile plz give me dtmf reciver circuit.
24th July 2010 07:39 AM
check out the CM8870. It's a full DTMF decoder with AF input via electret microphone.
Adjust AF amplification with P1. Pin15 (STD=Delayed Steering Output) goes high when a valid signal (SIGVALID) has been received, and serves as signal to read Q1 to Q4 (A0 to A3).
24th July 2010 06:38 PM
thx i will try kindly breef me wit detail plz
24th July 2010 06:43 PM
u mean pin 15 is high when output
and rn1a is grnd and other also grnd? (RN1B, RN1C and RN1D)
25th July 2010 09:36 AM
Pin15 goes high if a valid DTMF-tone combination has been received. RN1 is a four resistor array with a common ground pin meant as pull down resistor for the outputs Q1 through Q4 (A0 .. A3). Q1 .. Q4 are binary coded outputs with Q1 being the LSB.
Please download the data sheet and study it carefully. It also contains a look up table for binary outputs according to frequencies generated by DTMF devices.
Other than binary values the CM8870 decodes a 'Zero' being "0000", instead of "1010", provided by a binary coded switch.
So if you want to create a DTMF-lock don't use 'Zero'.
25th July 2010 05:09 PM
29th April 2012 08:57 AM
EDITED CKT..pnghi ,
i am interfacing dtmf 8870 with p89v51rd2, Need help with mt8870DE in myanmar-edited-ckt..png circuit attached
i am not getting desired led outputs by connecting nokia phone
RD pin of 8051 to be connected????
Last edited by gagandeep; 29th April 2012 at 08:58 AM.
Reason: circuit attached
29th April 2012 02:27 PM
I am in the West. Most of us Western people played with DTMF about 32 years ago. Unfortunately the internet was not used then so the articles about DTMF are not on the web today. Also cell phones (mobile phones?) were not used then.
Many printed magazines from the West about 32 years ago talked about DTMF.
29th April 2012 03:27 PM
How exactly are you getting the tones to the decoder. The drawing really does not show that part. What exactly happens with the LEDs?
Please do not PM me with forum related questions. Let's keep things in the open forum. Thank you.
30th April 2012 04:12 AM
Originally Posted by Reloadron
LEDs connected on o/p of dtmf
On reset - 0110
On pressing 1- 1000
on pressing keys leds glow for some time and again reset (0110)
even 8051 not responding
please check code
mov p1, #0ffh; // Port1 as input port
mov p2,#00h ; // Port2 as output port
mov a, p1;
cjne a,#0ffh, for1;
mov a, p1;
cjne a,#01h, for2 ;
mov a, p1;
cjne a,#02h, for1;
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