On Sunday 09 February 2003 01:50 am, you wrote:

Comments interspersed with code

> I am trying to read the temperature from a DS1620 and send this to a
> PC using the serial port, I know the serial portion of the code works
> I have already tested that. I am having trouble reading from the
> DS1620 and I wondered if anyone had any ideas on what I am doing
> wrong. Thanks.
>
> ;*******************************************************************
> ;Temperature
> ;*******************************************************************
>
>         LIST P=3D16F628, R=3DDEC    ; Use the PIC16F628 and decimal
> system
>
>         #include "P16F628.INC"  ; Include header file
>
>         __config  _INTRC_OSC_NOCLKOUT & _LVP_OFF & _WDT_OFF &
> _PWRTE_ON & _BODEN_ON
>
>         CBLOCK 0x20             ; Declare variable addresses starting
> at 0x20
>           dataL
>           tempw
>           count
>           Delay_i
>           Long_Delay_i
>           tmp
>         ENDC
>
>         #define  DQ     PORTB, 4
>         #define  CLK    PORTB, 5
>         #define  RST    PORTB, 6
>
>         ORG    0x000            ; Program starts at 0x000
> ;
> ; --------------------------------
> ; SET ANALOG/DIGITAL INPUTS PORT A
> ; --------------------------------
> ;
>         movlw   0x07
>         movwf   CMCON             ; CMCON=3D7 set comperators off
> ;
> ; ----------------
> ; INITIALIZE PORTS
> ; ----------------
> ;
>         movlw   0x0                     ; 00000000
>         movwf   PORTA
>
>         movlw   0x4                     ; 00000100
>         movwf   PORTB
>
>         bsf     STATUS,RP0          ; RAM PAGE 1
>
>         movlw   0xFF
>         movwf   TRISA             ; 11111111

Are all the PORTA pins connected to something? =20

>         movlw   0x12                        ; 00010010
>         movwf   TRISB
>
> ; ------------------------------------
> ; SET BAUD RATE TO COMMUNICATE WITH PC
> ; ------------------------------------
> ; Boot Baud Rate =3D 9600, No Parity, 1 Stop Bit
> ;
>         movlw   0x19              ; 0x19=3D9600 bps (0x0C=3D19200 bps)
>         movwf   SPBRG
>         movlw   0x24              ; brgh =3D high (2)
>         movwf   TXSTA             ; enable Async Transmission, set
> brgh
>
>         bcf     STATUS,RP0          ; RAM PAGE 0
>
>         movlw   0x90                    ; enable Async Reception
>         movwf   RCSTA
> ;
> ; ------------------------------------
> ; PROVIDE A SETTLING TIME FOR START UP
> ; ------------------------------------
> ;
>         bcf             RST
>         clrf    dataL
> settle  decfsz  dataL,F
>         goto    settle
>
>         movf    RCREG,W
>         movf    RCREG,W
>         movf    RCREG,W            ; flush receive buffer
> ;
> ; ---------
> ; MAIN LOOP
> ; ---------
> ;
> loop
>                 call    receive            ; wait for a char
>
>                 bsf     RST
>                 call    Delay
>                 movlw   0x0C
>                 call    sendDS
>
>                 movlw   0x03
>                 call    sendDS
>
>                 movlw   0xEE
>                 call    sendDS
>                 call    Delay
>
>                 movlw   0xAA
>                 call    sendDS
>                 call    Delay
>                 call    receiveDS
>                 bcf             RST
>                 call    send
>                 movlw   0x0D
>                 call    send
>                 movlw   0x0A
>                 call    send
>
>
>                 goto    loop
>
> ;
> ; -------------------------------------------
> ; RECEIVE CHARACTER FROM RS232 AND STORE IN W
> ; -------------------------------------------
> ; This routine does not return until a character is received.
> ;
> receive btfss   PIR1,RCIF         ; (5) check for received data
>         goto    receive
>
>         movf    RCREG,W            ; save received data in W
>         return
> ;
> ; -------------------------------------------------------------
> ; SEND CHARACTER IN W VIA RS232 AND WAIT UNTIL FINISHED SENDING
> ; -------------------------------------------------------------
> ;
> send    movwf   TXREG             ; send data in W
>
> TransWt bsf     STATUS,RP0          ; RAM PAGE 1
> WtHere  btfss   TXSTA,TRMT        ; (1) transmission is complete if
> hi goto    WtHere
>
>         bcf     STATUS,RP0          ; RAM PAGE 0
>         return
> ;
> ; --------------
> ; SEND TO DS1620
> ; --------------
> ;
> sendDS
>                 movwf   tempw
>                 movlw   8
>                 movwf   count
>                 bsf             STATUS,RP0      ;register page 1
>             bcf         DQ      ; Set data for output.
>             bcf         STATUS,RP0      ;register page 0

This is not cool at all.  Though this may work to access the TRISB=20
register, it's not at all clear.

> sendloop
>                 bcf     CLK
>                 btfsc   tempw, 0
>               bsf       DQ
>             btfss       tempw, 0
>               bcf       DQ
>             rrf         tempw, f
>             bsf         CLK
>                 decfsz  count
>                   goto  sendloop
>                 return
>
> ;
> ; -------------------
> ; RECEIVE FROM DS1620
> ; -------------------
> ;
> receiveDS
>                 movlw   8
>                 movwf   count
>                 bsf             STATUS,RP0      ;register page 1
>             bsf         DQ      ; Set data for input.
>             bcf         STATUS,RP0      ;register page 0
> receiveloop
>                 bcf     CLK
>                 rlf     tempw

Shouldn't the above line be "rlf   tempw, F"?  It looks like you are=20
dropping all your received bits.  IIRC, the default destination is W

>                 btfsc   DQ
>                   bsf   tempw, 0
>                 btfss   DQ
>                   bcf   tempw, 0
>                 bsf             CLK
>                 decfsz  count
>                   goto  receiveloop
>                 movf    tempw, w
>                 return
>
> Delay
>         movlw 0xff
>         movwf Delay_i
> L1     nop
>         decfsz Delay_i, f
>         goto L1
>         return
>
> Long_Delay
>         movwf tmp
>         movlw 0xff
>         movwf Long_Delay_i
> L2     call Delay
>         decfsz Long_Delay_i, f
>         goto L2
>         movf tmp,w
>         return
>
>         END

michael

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