Post by thread:DTMF decoder project

I am working on a dtmf decoder for a school project. I was wondering if anyone could help me write a well documented program for the 12C672 it is an 8 DIP package and I am using the holtek HT9170 which uses a four pin binary output. (output described below) Does anyone know a good LCD to use? Thanks, Robert Szasz spam_OUTRszaszTakeThisOuTpay.net digit pin a pin3 pin2 pin1 pin0 1 H L L L H 2 H L L H L 3 H L L H H 4 H L H L L 5 H L H L H 6 H L H H L 7 H L H H H 8 H H L L L 9 H H L L H 0 H H L H L # H H L H H * H H H L L a H H H L H b H H H H L c H H H H H d H L L L L - L - - - -

Looks like you've used 5 of your pins already, add power and ground and that gives you just 1 pin left. You could use this to drive a serial LCD display, or use it to gate the /OE pin on the decoder which means you can use the 5 signal pins for something. Unfortunately even driving a normal LCD in 4 bit mode needs 6 pins, so that may not help you much, unless you expand the I/O by using a shift register, which is probably the best option. Are you forced to use an 8 pin PIC? It would have been easier to use the 16F84 with it's higher pin count. Regards Mike Rigby-Jones > {Original Message removed}

Use HOLTEK HT1616M16 or SC1611M10T. It requires only two lines (clocked serial ) for data display. If you need the code to write to HT1616M16 or SC1611M10T email me privately. I have done DTMF decoding for CALLER ID with Holtek display. Regards Pailoor Robert Szasz wrote: {Quote hidden}> I am working on a dtmf decoder for a school project. I was wondering if > anyone could help me write a well documented program for the 12C672 it is an > 8 DIP package and I am using the holtek HT9170 which uses a four pin binary > output. (output described below) Does anyone know a good LCD to use? > Thanks, > Robert Szasz > .....RszaszKILLspam@spam@pay.net > > digit pin a pin3 pin2 pin1 pin0 > 1 H L L L H > 2 H L L H L > 3 H L L H H > 4 H L H L L > 5 H L H L H > 6 H L H H L > 7 H L H H H > 8 H H L L L > 9 H H L L H > 0 H H L H L > # H H L H H > * H H H L L > a H H H L H > b H H H H L > c H H H H H > d H L L L L > - L - - - - -- ================================================= For Embedded Controls Solutions and Custom Designs CHIP TECHNOLOGIES - Member, Microchip Consultant Program Bangalore - INDIA Email : chiptechKILLspamvsnl.com Webpage : http://business.vsnl.com/chiptech ( updated 16th April 1999 )

On Tue, 4 May 1999 23:44:03 -0700 Robert Szasz <.....rszaszKILLspam.....PALY.NET> writes: >I am working on a dtmf decoder for a school project. I was wondering >if >anyone could help me write a well documented program for the 12C672 it > Since only 6 of the pins of an 8 pin PIC are used for I/O, this project will quickly run out of pins. It is likely that several tricks and maybe some extra hardware would be needed to interface both the DTMF decoder and an LCD. Going to an 18-pin PIC would simplify things a lot. As for converting the 4-bit codes to ASCII characters to display, just use a 16-entry table. Put the binary outputs in order from LLLL to HHHH and write the corresponding ASCII into the table. The output from this chip looks like that from an 8870, in that case the conversion table would be: dt 'D1234567890#*ABC' To display a tone, read the 4-bit code from the DTMF chip and use it as an index from 0 to 15 into the table. Retrieve the corresponding ASCII code from the table and send it to the LCD. Is the HT9170 pin-compatible with the MT8870? I have a project which uses the latter chip but it is hard to find. ___________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com/getjuno.html or call Juno at (800) 654-JUNO [654-5866]