CRC code for DS1820

Archiver

Does anyone have a PBASIC routine to check/verify the scratch pad ram
CRC code for the DS1820?
Thanx,
-Barry

Archiver

Barry-

The program below will read the Serial ID and scratchpad for DS18S20,
plus calculate and verify the CRC. The CRC code implements the
standard Dallas Semi 8-bit CRC algorithm. Should work fine for the
'1820 as well.

Regards,

Steve

'{$STAMP BS2p}

id VAR BYTE(9)
i VAR BYTE
j VAR BYTE
k VAR BYTE
crc VAR BYTE
feedback VAR BIT

' display serial ID, CRC results
OWOUT 8,1,[noparse][[/noparse]$33]
OWIN 8,0,[noparse][[/noparse]STR id\8]
DEBUG "Serial ID: "
FOR i = 0 TO 7
DEBUG HEX2 id(i), " "
NEXT

crc = 0
FOR i = 0 TO 7
j = id(i): GOSUB addToCRC
NEXT
DEBUG CR,CR

' display scratchpad contents, CRC results
OWOUT 8,1,[noparse][[/noparse]$CC,$BE]
OWIN 8,0,[noparse][[/noparse]STR id\9]
DEBUG "Scratchpad: "
FOR i = 0 TO 8
DEBUG HEX2 id(i)," "
NEXT

crc = 0
FOR i = 0 TO 8
j = id(i): GOSUB addToCRC
NEXT
DEBUG CR,CR

STOP

addToCRC:
DEBUG CR,HEX2 j," "
FOR k = 0 TO 7
feedback = crc.BIT0 ^ j.BIT0
crc = crc >> 1 + (feedback*$80) ^ (feedback*$0C)
j = j >> 1
NEXT
DEBUG HEX2 crc," "
RETURN


On 2 Jan 04 at 17:20, prius_lover2002 wrote:

> Does anyone have a PBASIC routine to check/verify the scratch pad
> ram CRC code for the DS1820? Thanx, -Barry