Reading DS 1822 or DS1820 TH TL flags
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Posts: 46,084
I really need some help with the code needed to read the High and Low
temp Flags on these temp sensors I have not been able to find any
documintation for the actual code needed for this chore. I have the
spec sheets and have looked on the parallax sight but no one has
address the specifics of the code needed. when you search for a alarm
according to the flow chart you issue a convert T, then an alarm
search, then you issue a read scratchpad to see if a DS1822 has
issued a rom ser #, which I assume is the alarm code? Maybe?
temp Flags on these temp sensors I have not been able to find any
documintation for the actual code needed for this chore. I have the
spec sheets and have looked on the parallax sight but no one has
address the specifics of the code needed. when you search for a alarm
according to the flow chart you issue a convert T, then an alarm
search, then you issue a read scratchpad to see if a DS1822 has
issued a rom ser #, which I assume is the alarm code? Maybe?
Comments
I've been using the DS1615 and finding help for these can be tough. How are you
reading it now? Have any code we can look at?
Here is how I'd do it....I don't have one of these to play so take this with
grain of NaCl....[noparse]:)[/noparse]
First we pulse the data line to tell it to get ready. Pull the dataline low and
then high.
Wait till the return pulse done....a pause or maybe a loop to watch the
Dataline...when it's back to high we are ready to send commands.
Send the command...I'd use Shiftout. For a bus with many sensors you send out
the byte for "match Rom" 55 hex....then the 64 bit address....that's 9 bytes
total. The command might look like this...
shiftout dataline, sclk, lsbfirst, [noparse][[/noparse]$55,SN1,SN2,SN3,SN4,SN5,SN6,SN7,SN8]
I'm assuming you can ignore the clock line...no need for it anyway. If you only
have one device you can skip the rom...via
shiftout dataline, sclk, lsbfirst, [noparse][[/noparse]$CC]
Then send out "Read Scratchpad" or BE
shiftout dataline, sclk, lsbfirst, [noparse][[/noparse]$BE]
After that 9 bytes are coming your way....so you need to collect them and do
what you want with them. Your High and low values are byte 2 and 3 if you start
counting at 0
I guess shiftin works.....here is something close...
shiftin dataline, sclk, lsbpre, [noparse][[/noparse]temp1,temp2,TH,TL,crap1,crap2,CR,CP,CRC]
And there you have it, something to ponder. If you want to log temperature that
Ds1615 is pretty cool...plus I have working code for it! [noparse]:)[/noparse]
Good luck,
Let us know how it goes...
Tim
>>> j-beasley@c... 10/08/03 02:41PM >>>
I really need some help with the code needed to read the High and Low
temp Flags on these temp sensors I have not been able to find any
documintation for the actual code needed for this chore. I have the
spec sheets and have looked on the parallax sight but no one has
address the specifics of the code needed. when you search for a alarm
according to the flow chart you issue a convert T, then an alarm
search, then you issue a read scratchpad to see if a DS1822 has
issued a rom ser #, which I assume is the alarm code? Maybe?
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