dtmfout problem

[lerameur]

Hello,

I finally got my circuit working... well almost.
I use a pic chip with picbasic pro, I output DTMF and this goes through a filter shown in picbasic manual:
http://www.melabs.com/resources/pbpmanual/5_17-5_21.htm
From my scope I can see some 40v spike at the pin output and after the filter I do not see much maybe a few volts.
This goes directly to an audio transformer.
Is it normal to have 40v spike (the signal looks pretty nice). WHen I put a modem speaker at the pin output I can hear the dialing and maybe a third in strenght (sound) after the filter. At the output of the transformer I have an AC 250v capacitor. The pichip dials my phone, and I receive maybe 50% of the calls.
Should I be using the filter? (I am not using an amplifier as mentionned in the manual)
Is the 40v good to put directly on the transformer?
Also from the speaker I hear a lot of background noise

thanks
k

[mister_e]

Any real circuit and code of that? Are you using 20MHz crystal?

The noise is always there?

[Acetronics2]

Hi,

From the data I have here,...

I see a damping 680 Ohm res. on the Pic side of the line trafo. ( // with the winding !!! )

On the line side :

in series with the primary :

750 Ohms 2W // 1µF // TPJ ( to limit current to ~ 35 mA )

Alain

[lerameur]

Hi,
I am using 20Mz
I think the problem is more hardware than software..



code:/
'*************************
'* Alarm system dialer *
'*************************


'//////////////////////////////
'// Pic chip configuration //
'//////////////////////////////

INCLUDE "modedefs.bas" 'Includes supoprt for PicBasic language
@ DEVICE pic16F88,CCPMX_ON

' Setup Crystal oscillator Frequency to be used by PIC chip in MHz
DEFINE OSC 20 'use external 20mhz crystal

ANSEL = 1
CMCON = 7 ' Turn OFF the comparators so pins can be used as digital I/O-pins

'///////////////////////////////////////
'// Screen initialization //
'///////////////////////////////////////


DEFINE LCD_DREG PORTB ' Set LCD Data port
DEFINE LCD_DBIT 4 ' Set starting Data bit (0 or 4) if 4-bit bus
DEFINE LCD_RSREG PORTA ' Set LCD Register Select port
DEFINE LCD_RSBIT 2 ' Set LCD Register Select bit
DEFINE LCD_EREG PORTA ' Set LCD Enable port
DEFINE LCD_EBIT 3 ' Set LCD Enable bit
DEFINE LCD_BITS 4 ' Set LCD bus size (4 or 8 bits)
DEFINE LCD_LINES 2 ' Set number of lines on LCD

DEFINE LCD_COMMANDUS 2500
DEFINE LCD_DATAUS 250
DEFINE CHAR_PACING 2000
pause 2000


'/////////////////////////
'// PIN configuration //
'/////////////////////////

TRISA = %00011000 ' Set PORTA to all input
TRISB = %11111111 ' Set PORTB to all output
PortA = 0


'///////////////////////////////////////////////
'// Variable Declaration and initialization //
'///////////////////////////////////////////////


counter var byte
i var byte
counter=0


'//////////////////////////
'// Program starts here //
'//////////////////////////

Main:
lcdout $FE,1, "Counter:",dec counter
Pause 500

if PortA.4=1 then
counter=counter +1 'Counter at 1 dials phone number
goto Dial
endif

if PortA.4=0 then
counter=0
goto Main
endif

'//////////////////////////
'// End of program here //
'//////////////////////////

Dial:
'Determine which number to dial and dials it

lcdout $FE,1, "Dial:",dec counter
Pause 500

if counter =1 then 'begin counter loop
if PortB.0 = 1 then GOSUB Dial1760 'cel
if PortB.1 = 1 then GOSUB Dial4392 'Ken
if PortB.2 = 1 then GOSUB Dial9130 'Donald
if PortB.3 = 1 then GOSUB Dial758 'Lyne
Else
counter =1
goto Main
endif 'end counter loop

Pause 1000 'pause for 1 seconds
if (counter > 1) or (counter =0) then counter =1

'Keep counter to 1 after dialing, otherwise the program will keep dialing the number
' Will only redial if counter goes back to 0, that is alarm siren off

goto Main



'*************** subroutine here ********************
Dial1760: 'cel
lcdout $FE,1, "dialing1760 ",dec counter
Pause 500
PortA.1 = 1
pause 3000
DTMFOUT PortA.0, [5,1,4,4,4,4,4,4,4,2]
pause 4000 'Pause 4 seconds
DTMFOUT PortA.0, 20000,0, [5]
pause 2000 'Pause 2 seconds
PortA.1 = 0
return

end

/end code

[lerameur]

I think I might got the probe switch to 10x instead of 1x.. that would explain the 40v. I will check it once I get home...
if so I guess I would have would have something like 3.7v output peaks on the pin.

[lerameur]

Ok , the scoipe was set at 100x. now I read 4v at the output, but still a lot of noise after the filter, and only dials 50% of the times

k