ok, I understand what you're saying here. The thing I need to make understood is that I'm not wanting to flash an LED. Maybe I made a mistake mentioning the LED. What I need to do is have a 12F675 PIC react to a square wave on an input pin. The signal is an active low and goes from 0-5vdc with a 50% duty cycle. What the signal does is flash an LED and I need to tap into that signal. It's that signal, in conjunction with another signal (which I got covered), that changes the state of an output pin. Thank you for the info. I have definitely learned something new. ----- Original Message ----- From: "Steve Smith" To: "'Microcontroller discussion list - Public.'" Sent: Tuesday, November 21, 2006 5:17 PM Subject: RE: [PIC] Detecting a square wave > OK basic lesson before you get Olinized... > > This section is written for a '629 in MPlab (untested but should work) > > list p=12F629 ; PROCESSOR > include "P12f629.inc" ; INCLUDE FILE > __CONFIG _IntRC_OSC & _MCLRE_OFF ; SETUP OPTIONS > Org 00h > Goto PORT_SETUP > > Org 04h > Return ; this avoids the interrupt as its not used > > PORT_SETUP > clrf GPIO ; clears the port > latches > bsf STATUS,RP0 ; goes to bank 1 for > direction reg > movlw b'11000001' ; set up io > (1=input) > movwf TRISIO ; and save > > CMCON_SETUP > movlw b'00000111' > clrf CMCON ; set up for digital > > bsf STATUS,RP0 ; back to bank 0 > > ; when you get here you have a working (basic) chip with an input on GP0. > and an output on GP1. Use an external 10K pull-up resistor and a > pushbutton > switch to Vss on bit 0 and a led and resistor on bit 1 to VCC > > Its quick and dirty but the led will then follow the switch this is the > closest thing to "flash the led" that a novice can learn > > START_CODE > > BTFSS GPIO,0 ; Check the switch is off > GOTO $-1 ; no go back one > BSF GPIO,1 ; Led Off > BTFSC GPIO,0 ; check the is on > GOTO $-1 ; no go back one > BCF GPIO,1 ; Led On > Goto START_CODE ; repeat. > > Now you have found a square wave input and copied it to a pin so you can > see > it working > > Everybody gotta start somwhere > Regards Steve > > -----Original Message----- > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf > Of > dax2@hotmail.com > Sent: 21 November 2006 21:30 > To: Microcontroller discussion list - Public. > Subject: Re: [PIC] Detecting a square wave > > The project that I'm doing interfaces with other equipment. > The LED indicates if the unit is in standby or not. It flashes fairly > fast, > about 4-5 times a second. > I need to use it in conjunction with an audio signal (music) which is > being > handled by a detector. It will force the unit out of standby when the > music > starts. Then force it back into standby when the music is over. > I admit that I looked at the posts about using leading/falling edges but > to > be honest I haven't got a clue as to how to implement that code. > I tried using the port digitally. I figured the LED flashed slow enough > (in > > processor time) that it would eventually see the low. Didn't work. > What I originally tried with the comparator was to set one input high and > the other to the LED signal. Then I polled the interrupt (CMIF) to see if > the signal dropped. > Didn't work. > This is just my second PIC project. > > ----- Original Message ----- > From: "Andre Abelian" > To: "Microcontroller discussion list - Public." > Sent: Tuesday, November 21, 2006 3:22 PM > Subject: RE: [PIC] Detecting a square wave > >> directly connect to any of external interrupt input and >> fallow rising or falling edge. >> I do not any reason to use comparator >> >> Andre >> >> >> >> >> >> -----Original Message----- >> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu]On Behalf >> Of dax2@hotmail.com >> Sent: Tuesday, November 21, 2006 10:57 AM >> To: piclist@mit.edu >> Subject: [PIC] Detecting a square wave >> >> >> I have a project that requires me to detect a blinking LED. >> I'm using a 12F675 PIC. >> The signal to the LED is a 5v 50% duty cycle signal when it's on. >> A solid 5v when it's off. >> I tried to use the comparator but apparently I'm doing something wrong. >> Can someone point me in the right direction, please? >> -- >> http://www.piclist.com PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> >> -- >> http://www.piclist.com PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist