Are you using a PIC that has the pin to emulate a smaller pin device?

alan smith wrote:

>OK...i've pulled the code over to this machine so I
>can provide some more details.  I didnt want to cloud
>the issue, because I've found that port I/O behaves
>the same pretty much over the family of parts.
>
>Loading the canned code on the board, appears to be
>functioning ok. I suppose I could just write a routine
>to exercise the button on the board as well.
>
>The device is a 18F8720 on the Microchip tqfp dev
>board.  When I asked different, meant different from
>the 16F family of devices.  I'm not using TMR1 in this
>particular design, TMR0 and TMR2
>
>For setup I have
>
>#define	SHT_DATA_PIN	LATC,1
>#define SHT_DATA_DIR	TRISC,1
>#define	SHT_DATAin_PIN	PORTC,1
>#define SHT_CLK_PIN	LATC,0
>#define	SHT_CLK_DIR	TRISC,0
>
>#define FLAG		LATH,2
>#define FLAG_DIR	TRISH,2
>
>Where FLAG is being used so I can see where things are
>occuring via the logic analyzer.
>
>Here is the top part of the code.  During the section
>where its looking at the internal register SHT_Byte,
>it branches fine.  When looking for the ACK, it doesnt
>appear to be reading the port.  The SHT is pulling the
>data line low indicating the ACK is occuring but the
>code just blows right thru it as if it occurs EVEN if
>it didnt really occur.  Its not so much an issue on
>the ACK (other than if it didnt respond I'd like to
>know about it) but when I go to look for the data
>being valid (data line pulled back low after 250mS) it
>ignores the fact the data line is still high and
>attempts to read out of the device and the data is
>bogus.
>
>----------------------------------------------------------------
>;				SHT71 interface routine
>; Sends a command to the SHT71 temp/humidity sensor
>and retrieves
>; a two-byte response. The command is already in
>SHT_Byte
>
>SHT_TxRx
>
>	bsf	FLAG	; flag for analyzer					
>	; set SHT71 data line to an output
>	bcf	SHT_DATA_DIR		
>								; Send the transmission start sequence
>	bsf	SHT_DATA_PIN			
>	bsf	SHT_CLK_PIN			
>	bcf	SHT_DATA_PIN			
>	bcf	SHT_CLK_PIN			
>	nop
>	nop
>	nop
>	bsf	SHT_CLK_PIN			
>	bsf	SHT_DATA_PIN			
>	bcf	FLAG	
>
>; counter to loop through the eight bits to send
>	movlw	8
>	movwf	Byte_Count					
>
>SHT_SendBitLoop
>	bcf	SHT_CLK_PIN			
>	btfss	SHT_Byte,7			
>	bra	SHT_SendZero			
>	bsf	SHT_DATA_PIN			
>	bra	SHT_SendBit
>SHT_SendZero
>	bcf	SHT_DATA_PIN			
>SHT_SendBit
>	bsf	SHT_CLK_PIN			
>	rlncf	SHT_Byte,F				
>	decfsz	Byte_Count,F				
>	bra	SHT_SendBitLoop			
>	bcf	SHT_CLK_PIN			
>	bsf	SHT_DATA_DIR	
>			
>
>; now look for an ack (SHT71 pulls data line
>low--should
>; have occured on the last rise of the SCK line).
>
>	nop
>
>SHT_WaitAck		
>	btfss	SHT_DATAin_PIN,ACCESS		
>	goto	SHT_AckOK				
>	bsf	ERRORS,noACK			
>	return						
>
>
>
>
>
>		
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