Thanks very much for the code.
I am searching now for the dew point computation in picbasic pro !

Thanks a lot for the help

Ambrogio
IW2FVO


Quote Originally Posted by scalerobotics View Post
A quick google search got me to here for some basic stamp code. It may help. You could also search sht75 on this site for some more hits.

http://www.emesystems.com/OL2sht1x.htm

Please don't double post. I moved your post to this thread, even though it is pretty much the same as the first post.

Code:
'{$STAMP BS2}
' SHT15.bs2 version C
' (c) 2002, 2004 Tracy Allen, http://www.emesystems.com
' access the Sensirion model sht11 or sht15
' humidity and temperature chip
' temperature to xx.x degrees Celsius, RH to xx.x %
' Repeatedly shows raw data and converted values on debug screen.
' version B, corrects glaring error in humidity computation
' also adjusts timeout to allow use with faster stamps too.
' version C updates the math for temperature compensation of %RH
' and enables display of negative temperatures
' hookup sht11 or sht15 as follows for this program
'
' STAMP                 SENSIRION
'               220
' p1 ----o-----/\/\---o--pin 3 sck, clock
'                     |
'        ;---/\/\-----' pull-down
'        | 4.7k
' Vss--o-o---------------pin 1 common
'      |
'     ===  0.1uf
'      |             
' Vdd--o-o---------------pin 4 +5 volts
'        |    4.7k
'        '---/\/\-----; pull-up
'                     |
'              220    |
' p0 ----------/\/\---o--pin 2 dta, data
'                       
'
' The following code does not implement the CRC checking
 
 
sck PIN 1
dta PIN 0 ' note, 5k-10k pull-up, also 330ohm between the dta on stamp to dta on sht
dtain var in0
 
shtTR CON 3 ' read temperature
shtRH CON 5 ' read humidity
shtSW CON 6 ' status register write
shtSR CON 7 ' status register read
shtS0 CON 30 ' restore status register defaults (be sure to delay 11 milliseconds)
 
cmd VAR Byte
result VAR Word ' raw result from sht, also used as counter
r0 VAR result.byte0
r1 VAR result.byte1
degC VAR Word ' degrees Celsius * 100
RH VAR Word ' %RH * 10
RHtc VAR Word ' for temperature compensation of RH
 
initialize:
 outs=0
 dirs=%1111111111111101
 GOSUB shtrst ' reset communication with sht
 
DO
 getTemperature:
 cmd=shtTR ' temperature command to sht
 GOSUB shtget16
 degC=result+5/10-400 ' from 100ths to 10ths of a degree with rounding
 DEBUG tab,REP "-"\degC.bit15,DEC ABS degC/10,".",DEC1 ABS degC
 getHumidity:
 cmd=shtRH ' humidity command to sht
 GOSUB shtget16
 RH=(26542-(54722**result+result))**result-40
 ' temperature compensation follows:
 RHtc=655+(result*5)+(result**15917) ' intermediate factor
 RHtc=(RHtc**(degC+2480))-(RHtc**2730)+RH ' compensated value
 DEBUG tab, DEC result,tab,"%RH=",DEC RH/10,".",DEC1 RH
 DEBUG tab,"%RHtc=",DEC RHtc/10,".",DEC1 RHtc,cr
 PAUSE 1000
LOOP
 
' initializes communication with sht 
shtRst:
 SHIFTOUT dta,sck,lsbfirst,[$ffff\16]
RETURN
 
' get 16 bits of data, enter with command in "cmd"
shtget16:
 gosub shtcmd ' send the command "cmd"
 gosub shtwait ' wait for command to finish
 shiftin dta,sck,msbpre,[r1] ' msbyte
 low dta ' acknowledge
 pulsout sck,10
 input dta
 shiftin dta,sck,msbpre,[r0] ' lsbyte
 input dta ' terminate communication
 pulsout sck,10
return
 
' send start sequence and command
shtcmd:
shtStart: ' send the start sequence
 ' dta: ~~~~~|_____|~~~~~~
 ' sck: ___|~~~|_|~~~~|____
 ' while dta is low, clock goes low and then high
 input dta ' pullup high
 high sck
 low dta
 low sck
 high sck
 input dta
 low sck
shtcmd1: ' send the command
 shiftout dta,sck,msbfirst,[cmd]
 input dta ' allow acknowledge
 pulsout sck,10
return
 
shtWait:
 ' wait for sht to pull data pin low
 ' or for time out
 result=4096
 DO
 result=result-1
 LOOP WHILE dta & result.bit11
 RETURN
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