Pic output low signal

[amitaiwe]

Hi,

All communications like USART, SPI, I2C need exacting timings to be able to work with the devices they connect to.

Your best way forward is to look for a Pic project that does the detecting but from a standard port pin/s so allowing you to use a proper crystal as the main oscillator which then allows you to run the program code and communications properly.

Thanks again for all the Patience,

I don't intend changing or interfering with the crystal oscillation .
What I want to do is as follows:
Using the clock out pin of the pic as the clock for the SPI protocol and using the same
output to connect to a inductor and from there to the SPI receiver pin and then compare
to the previous result.

The reason i want to use a SPI protocol is because as I see it oscillating a freq.
via a PIO is implemented by clearing and setting a single bit and in order to be able
to see changes in the freq. a register result is need and not a bit change.
I'm attaching a code which I thought of using in the first place for implementing the idea
and I didn't see any way for the part of getting the change of frequency information.


I hope I'm clear enough, Amitai

		LIST P=PIC16F877
		include <P16f877.inc>

		org			0x00
reset:	goto		start

		org			0x04
start:	bcf			STATUS, RP1
		bsf			STATUS, RP0		;bank 1
;------------------------------------------------------------------------------
		movlw		0xFE
		movwf		TRISC			;portC: RC0-Output
;------------------------------------------------------------------------------
		bcf			STATUS, RP0		;bank 0

LOOP:	bsf			PORTC,0			;RC0 = '1'
		call		DELAY_1m
		bcf			PORTC,0			;RC0 = '0'
		call		DELAY_1m
		goto		LOOP

;------------------------------------------------------------------------------

DELAY_1m:
		movlw		0x2f			;  N1 = 47
		movwf		0x30
cont2:	movlw		0x10			;  N2 = 16
		movwf		0x31
cont1:	decfsz		0x31,1
		goto		cont1
		decfsz		0x30,1
		goto		cont2
		return						

;------------------------------------------------------------------------------

		end

- - - Updated - - -

I have now also a PIC16f88 which has an internal osc. and using it
I can be sure that I don't change somehow the pic's routine freq. , and it
seems to have the same functions which I need as the PIC16f877

Amitai

 

[milan.rajik]

If the PIC has hardware SPI then it will generate clock for slave.

 

[amitaiwe]

TO make it more simple: create a frequency by the pic and receiving a frequency by the pic. (the compare can be left out in
the mean time)

Amitai