I'm trying to interface a Dalsemi DS1721 Temp chip to the i2c bus of a
PIC16F877...
Everything seems to work for a little bit, I tell the DS1721 to start free
running mode with
default setup, then start looping and reading the temp every 2 seconds or so..
but after 5 or so reads of the temperature the PIC locks up in the temp
recieve macro..
The macros are based off John Sand's stuff on the piclist page and are as
follows:

This function initilizes the DS1721...seems to work ok
init_temp
        call    start_i2c
        movlw   TEMP_ADDR_W
        movwf   SSPBUF
        call    wait_for_ack_i2c

        movlw   TEMP_STC                ; Send StarT Conversion
        movwf   SSPBUF
        call    wait_for_ack_i2c        ; Get ACK
        call    stop_i2c
        return

This one reads the current temp from the chip, locks up at some point, cant
tell
where due to lack of any debugging hardware.

read_temp
        call    start_i2c               ; Send Start bit

        movlw   TEMP_ADDR_W
        movwf   SSPBUF
        call    wait_for_ack_i2c

        movlw   TEMP_RT                 ; Send Read Temp
        movwf   SSPBUF
        call    wait_for_ack_i2c        ; Wait for ACK

        call    start_i2c               ; Send start again

        movlw   TEMP_ADDR_R             ; Send read address
        movwf   SSPBUF
        call    wait_for_ack_i2c        ; Wait for ACK

        call    enable_receive_i2c      ; Get temperature MSB
        movf    SSPBUF, W
        movwf   Local_TempMSB           ; Save it

        call    enable_receive_i2c      ; Get temperature LSB
        movf    SSPBUF, W
        movwf   Local_TempLSB           ; Save it

        call    stop_i2c                ; We done
        return

Again the call'd functions in these are John Sand's at
http://www.piclist.com/techref/microchip/i2c87xjs.htm.
Anyone have any idea what I'm doing wrong? BTW i added the mono. cap on the
SDA line to correct the 16F877's
I2C bug.

Thanks in advance,
Tim Thompson


-
Remember, 'kill' doesn't kill processes, users kill processes.

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