Sensirion SHT11 with a PIC16F628-20

gbm_designs · - 14th November 2004, 15:20

Greetings-

I 've recently moved from the BS2 to the PIC Basic Compiler Pro software.

I'm trying to attach a Sensirion SHT11 Temperature and Humidity sensor to the Pic 16F628-20 and then send the Calculated values in Celcius and Farenheit, as well as Relative Humidity %RH to the COM1 port on my windows machine.

I have found many sample source code, but none seem to work for me when I compile. Either written for a separate compiler, or a different chip, so the #Include statements are wrong.

Can anyone help me along here? I would really appreciate it.

If any other information is required, please let me know.

Thank you,

Christian
EPIC PROGRAMMER
PIC BASIC COMPILER PRO
16F628-20
20-MHz External Xtal

**NavMicroSystems** · - 14th November 2004, 18:05

attached is a working piece of code for the 16F628

Code:

___________________

' Temperature, Relative Humidity and Dewpoint
' Processor : 16F628
' Sensor    : SHT1x / SHT7x
' Display   : 16x2

'** Pin-Assingments

dta     VAR PORTB.1     ' Sensor Data
clk     VAR PORTB.0     ' Sensor Clock

'** Constants

cmdtr     CON %00000011    ' Command "read temperature"
cmdhr     CON %00000101    ' Command "read humitity"

'** Variables

result     VAR WORD    ' RAW Data from Sensor
chksum     VAR BYTE     ' Checksum
cmd     VAR WORD    ' Sensor Command
RHlin     VAR WORD    ' Rel. Humidity (RH) Linear (% *10)
RHtc    VAR WORD    ' Rel. Humidity (RH) temp. compensated (% *10)
Temp     VAR WORD    ' Temperature (°C *100)
DP     VAR WORD    ' Dewpiont (°C *10)


'** Temp variables used in div. calculations

TempDP  VAR WORD
Rchk     VAR BYTE 
logEW     VAR WORD
sign     VAR BIT
wy        VAR WORD
wz        VAR WORD
wj        VAR WORD
wx      VAR WORD
i     VAR BYTE
ix     VAR BYTE
bt     VAR BIT


Pause 500
LCDOut $FE,1,"**   SHT 11   **"
PAUSE 1000

main:

GoSub init
cmd = cmdtr

GoSub readsensor
Temp=result-3995

GoSub init
cmd = cmdhr

GoSub readsensor
RHlin=(26542-(54722**result+result))**result-40  ' RH linear
RHtc=655+(result*5)+(result**15917)                 
RHtc=(RHtc**(Temp/10+2480))-(RHtc**2730)+RHlin   ' RH temp. compensated

GoSub dewpoint

LCDOut $FE,$80," ",$DF,"C","   ",$25,"RH","    DP "
LCDOut $FE,$C0,DEC2 (TEMP/100),".",DEC1 (temp/10),"  ",DEC2 RHTC/10,".",DEC1 RHTC,"  ",DEC2 ABS DP/10,".",DEC1 ABS dp
sleep 10
GoTo main

'** Init Sensor
init:                                             
High dta 
Low clk 
For i=1 to 10 
High clk
Pause 1 
Low clk
Pause 1 
Next i 
Call tstart 
Return 

'** start transfer
tstart:
High clk
Pause 1 
Low dta 
Pause 1 
Low clk
Pause 1 
High clk
Pause 1 
High dta 
Pause 1 
Low clk
Return 

'** get Data from Sensor
readsensor:
GoSub tstart
GoSub WaitSensor

ShiftOut dta,clk,1,[cmd\8]                  ' send command
Input dta                      ' wait acknowledge 
Low clk
While dta=1 
Wend
PulsOut clk,10                      ' send ack 
While dta=0 
Wend
While dta=1                      ' wait for conversion to complete
Wend 
Low clk
ShiftIn dta,clk,0,[result.highbyte\8]          ' get first byte
Low dta 
PulsOut clk,10                      ' send ack 
ShiftIn dta,clk,0,[result.lowbyte\8]             ' get second byte
Low dta 
PulsOut clk,10                      ' send ack 
ShiftIn dta,clk,0,[chksum\8]                     ' get third byte (checksum)
High dta 
PulsOut clk,10                      ' send ack 
Input dta                      ' End of Transmission
Input clk                          

Return

'** Dewpoint Calculation
    ' See: SENSIRION Application Note "Dewpoint Calculation"
    ' logEW = (0.66077+7.5*T/(237.3+T)+(log(RH)-2)
      ' DP = ((0.66077-logEW)*237.3)/(logEW-8.16077)

DewPoint:
  
  TempDP=Temp/10
  logEW=6608
  sign=TempDP.bit15
  wz=ABS TempDP
  wx=(7*wz)+(wz/2)                              
  wy=2373+wz
  wj=wx/wy
   For ix=15 to 0 step -1
    wx=(wx//wy)<<1
    wz.bit0(ix)=wx/wy
   Next
  wx=(-sign^((wj*10000)+(wz**10000)))+sign        
  logEW=wx+logEW
  wx=RHtc
  wj=(NCD wx) - 1
  wx=wx<<(15-wj)
  wz=0
  For ix=14 to 0 step -1
    wy=wx**wx
    wz.bit0(ix)=wy.bit15
    bt=~wy.bit15
    wx=(wy<<bt)+(bt && wx.bit15)
   Next
  
  wx=((wj*4000)**49321)+(wz**6021)
  logEW=wx+logEW-30000            
  sign=logEW.bit15
  logEW=(-sign^(((ABS logEW)+2)/4))+sign
  wx=1652-logEW
  sign=~wx.bit15
  wx=ABS wx
  wy=20402-logEW
  wj=wx/wy
  
   For ix=15 to 0 step -1
    wx=(wx//wy)<<1
    wz.bit0(ix)=wx/wy
   Next
  
  DP=((23730**wz)+5)/10
  DP=(-sign^DP)+sign

Return

WaitSensor:
  result=4096
Loop:
  result=result-1
   IF dta && result.bit11 Then Loop
  Return
End
___________________

Regards

Ralph

gbm_designs · - 14th November 2004, 19:20

Greetings Ralph-

Thank you for your help.

PROBLEMS:

PROBLEM1.
I get a COMPILE ERROR in this Section of Code:

DewPoint:

For ix=14 to 0 step -1
wy=wx**wx
wz.bit0(ix)=wy.bit15
bt=~wy.bit15
wx=(wy< Next <<<<---------THIS IS THE PROBLEM

QUESTION: Can you let me know what's missing here?

************************
PROBLEM2:
After COMMENTING out the ERROR LINE is PROB1, I set up the circuit as described below ((SEE CIRCUIT SPECS)) and use Hyperterminal to view the Output of the Program by COMMENTING out the LCD output in your code and replacing it with the following:

SerOut2 PORTB.2,86,[DEC2 (TEMP/100),".",DEC1 (temp/10)," ",DEC2 (TEMP/100),".",DEC1 (temp/10)," ",DEC2 RHTC/10,".",DEC1 RHTC," ",DEC2 ABS DP/10,".",DEC1 ABS dp,13,10]
'LCDOut $FE,$C0,DEC2 (TEMP/100),".",DEC1 (temp/10)," ",DEC2 RHTC/10,".",DEC1 RHTC," ",DEC2 ABS DP/10,".",DEC1 ABS dp

WHAT HAPPENS: I get the SAME Values over and over again

** SHT 11 **
12.8 00.4 12.3
12.8 12.8 00.4 12.3

QUESTION: ANY IDEAS?

************************

CIRCUIT SPECS:

PIC16F628-20
PINOUTS
4-----MCLR---4.7kohm to 5vdc
5-----VSS-----GND
6-----RB0-----Pin3 of SHT11 (SCK)
7-----RB1-----Pin2 of SHT11 (Data)
8-----RB2-----Pin10 of MAX232 (T2IN)
15---OSC2---XTAL (4Mhz)
16---OSC1---XTAL (4Mhz)

SHT11
PINOUTS
1----GND----GND
2----DATA---Pin7 of PIC (RB1)
3----SCK --- Pin6 of PIC (RB0)
4----VDD----5VDC

THANKS,

I hope this description is complete enough

CHRISTIAN

**NavMicroSystems** · - 14th November 2004, 19:27

Christian,

initially I tried to post the example using " [ code ] ... [ /code ] "

when I viewed my posting I had to realize the code was truncated at some point.

I have edited my posting and the full code is now there as plain ASCII.

please reload the code.

regards

Ralph

gbm_designs · - 14th November 2004, 19:38

Greetings Ralph-

It appears that the source code is the same.

I did a quick line comparison and the same number of characters are present.

Could you e-mail it to me?

Thank you

mailto: [email protected]

Christian

**NavMicroSystems** · - 14th November 2004, 19:50

. . .Could you e-mail it to me?

DONE!

gbm_designs · - 14th November 2004, 19:59

Greetings Ralph-

Thank you for the E-mail.

I used the new code with my changes for the Serial Port, rather than LCD.

However I still get the same value over and over.

** SHT 11 **
RH DP •
12.8 12.8 00.4 14.9

RH DP •
12.8 12.8 00.4 14.9

Kind of odd.

I re-tested this SHT11 Device with my BS2 Program and hardware and it works fine.

I have GOT to be doing something WRONG.

Christian

**NavMicroSystems** · - 14th November 2004, 20:03

Christian,

I'll have a look at it tomorrow morning when I'm back at my desk.

regards

Ralph

gbm_designs · - 14th November 2004, 20:05

I'll keep banging away at it tonight also.

I'll let you know what I find.

Christian

**cibotsan** · - 19th May 2006, 10:13

hi! iam also working SHT11 project with PIC16F877 display with LCD, itry Ralph source code but, only **SHT 11** display no sensor reading ,can someone email source code to me? [email protected]
thanks

**ronf** · - 24th October 2006, 19:07

For anyone trying to get this first off, add wx=wy<< bt+(bt & wx.bit15)
instead of the truncated part Christian had indicated.
(nice work on the code Ralph)
This works fine on a PIC16F876A 20mhz using portc.3 and portc.4
I can see why Ralph had problems with it not posting properly. I had to
put in a space before the first bt to see it properly as without the space
it was truncating my reply too. Anyone else have a problem posting code
like this?
(helps to look at the preview)
Hope this helps someone.
Ron

**Evolution** · - 12th March 2007, 17:59

I have been trying to get this code to work for the last week,A friend and i have both recived samples and have been unable to get the project going after overcoming the first compile error it seems that the device wont respond and it just hangs in the readsensor routine, Could yoiu please post the working picbasic pro or email it to me at [email protected].
it seems that if i force data line to go low by shorting to ground the code execution continues and outputs repative numbers.
There is a misplaced next could you please clarafy where this is ment to go

regards Evolution

**Acetronics2** · - 12th March 2007, 18:27

just see that ...

http://www.parallax.com/dl/src/prod/shtdocscode.zip

Alain

Original · - 15th November 2004, 00:27

Look at this:

Code:

'*******************************[ SHT11 Sample Code ]********************************
' File...... SHT11.bas
' Purpose... SHT11 digital humidity sensor sample code
' MCU....... Microchip PIC16F877
' Software.. Converted to Proton+ 2.0 from PBPro ver 2.4
' Author.... Brandon Tarr
' E-Mail.... [email protected]
' Web....... http://www.spectrumedix.com
' Started... May 15, 2002
' Updated... 
' Version... 1.0                                               
'**************************************************************************

 device 16f877

DEFINE xtal 4
Define  LCD_DREG        PORTD
Define  LCD_DBIT        4
Define  LCD_RSREG       PORTE
Define  LCD_RSBIT       0
Define  LCD_EREG        PORTE
Define  LCD_EBIT        1

TEMP            con     1
HUMI            con     2
                                        ' adr   command r/w
Symbol statusregw      =     $06             ' 000   0011    0
Symbol statusregr      =     $07             ' 000   0011    1
Symbol measuretemp     =     $03             ' 000   0001    1
Symbol measurehumi     =     $05             ' 000   0010    1
Symbol resett           =     $1e             ' 000   1111    0

' -----[ Variables ]---------------------------------------------------------------------
Dim SCK         as     PORTC.3             ' SHT11 SCK
Dim SDATA       as     PORTC.4             ' SHT11 DATA

Dim i           as     byte
Dim f           as     byte
Dim value       as     byte
Dim errorr       as     bit
Dim mode        as     byte
Dim ack         as     bit

Dim vall         as     byte
Dim pktvalue    as     word
Dim pktchksum   as     byte

Dim humival     as     word
Dim tempval     as     word
Dim dewpoint    as     byte
Dim checksum    as     byte

' -----[ Initialization ]----------------------------------------------------------------
ADCON1 = 7              ' Set PORTA and PORTE to digital
Low PORTE.2             ' LCD R/W line low (W)
Pause 100               ' Wait for LCD to start
lcdout $fe, 1

' -----[ Main Code ]---------------------------------------------------------------------
usetheSHT11:
gosub connectionreset
value = measurehumi
gosub measure                                        ' measure humidity
humival = pktvalue * 1000
humival = DIV32 4095
lcdout $fe, 2, "                    ", $fe, 2, "Humidity: ", dec humival / 10, ".", dec humival // 10, "%"
value = measuretemp
gosub measure                                        ' measure temperature
tempval = pktvalue * 1000
tempval = DIV32 16383
lcdout $fe, $c0, "                    ", $fe, $c0, "Temperature: ", dec tempval / 10, ".", dec tempval // 10, 223, "C"
pause 100                                            ' decrease sample time
goto usetheSHT11

' -----[ Subroutines ]-------------------------------------------------------------------
connectionreset:            
' communication reset: DATA line is high and at least 9 SCK cycles followed by transstart
'         ________________________________________       _____
' SDATA:                                          |_____|
'           _   _   _   _   _   _   _   _   _     __    __
'   SCK:  _| |_| |_| |_| |_| |_| |_| |_| |_| |___|  |__|  |___
high SDATA
low SCK                                 ' set initial state
for i = 1 to 9                          ' 9 SCK cycles
    high SCK
    low SCK
next
gosub transstart                       ' transmission start
return

transstart:                             
' generates a transmission start 
'         ___       _____
' SDATA:     |_____|
'            __    __
'   SCK:  __|  |__|  |___

high SDATA
low SCK                                 ' set initial state
high SCK
low SDATA
low SCK
high SCK
high SDATA
low SCK
return

measure:
' makes a measurement (humidity/temperature) with checksum
errorr = 0
gosub transstart                        ' transmission start
gosub writebyte
for i = 1 to 255                        ' wait until sensor has finished the measurement
    if SDATA = 0 then
        goto meascomplete
    endif
    pause 1
next 
meascomplete:
if SDATA != 0 then                      ' or timeout (~2 sec.) is reached
    errorr = 1
endif
ack = 1
gosub readbyte                          ' read the first byte (MSB)
pktvalue.highbyte = vall
gosub readbyte                          ' read the second byte (LSB)
pktvalue.lowbyte = vall
ack = 0
gosub readbyte                          ' read checksum (no acknowledge to put sensor in "sleep" mode)
pktchksum = vall
return

writebyte:
' writes a byte on the Sensibus and checks the acknowledge
errorr = 0
i = $80
while i > 0
    if (i & value) != 0 then              ' masking value with i
        high SDATA                        ' write to SENSI-BUS
    else
        low SDATA
    endif
    high SCK                            ' clk for SENSI-BUS
    low SCK
    i = i / 2                           ' shift bit for masking
wend
high SDATA                              
TRISC.4 = 1                             ' release SDATA-line
high SCK                                ' clk #9 for ack
errorr = SDATA                           ' check ack (SDATA will be pulled down by SHTXX)
low SCK
return

readbyte:
' reads a byte from the Sensibus and gives an acknowledge in case of "ack=1"
vall = 0
high SDATA                              
TRISC.4 = 1                             ' release SDATA-line
i = $80
while i > 0
    high SCK                            ' clk for SENSI-BUS
    if SDATA = 1 then                   ' read bit
        vall = vall | i
    endif
    low SCK
    i = i / 2
wend
TRISC.4 = 0                             ' grab SDATA-line
SDATA = ack                            ' in case of "ack", pull down DATA-Line
high SCK                                ' clk #9 for ack
low SCK
high SDATA                              
TRISC.4 = 1                             ' release SDATA-line
return

softreset:
' resets the sensor by a softreset
errorr = 0
GOSUB connectionreset                   ' reset communication
value = resett
gosub writebyte                         ' send RESET-command to sensor
return

**adamchapman** · - 23rd August 2007, 05:18

I'm using the above code with a 16f84a and getting a consistent number, which is clearly wrong. I'm getting humvalue 16003 and tempval 4000. And since I haven't burst into flames this seems unlikely to be accurate.

I also tried using a modified Keunyoung Oh's code for the 16f877 (found http://itp.nyu.edu/physcomp/sensors/Code/SHT11 ) but received similar results (consistent & wildly inaccurate numbers), though with different numbers.

Any idea why this might be?

Also, as a possible explanation: I'm using the DIP sht11 which has a 117 on the sensor. I'm assuming I should use the pin diagram which goes with sensirion sht11 sensor module #28018, but all the other pin diagrams are different.

any suggestions would be helpful.

thanks,
Adam

**adamchapman** · - 23rd August 2007, 21:50

here's the full code I'm currently (trying to use) everything compiles and publishes in PBP, but still no good data. is my code messed up?

Code:

'*******************************[ SHT11 Sample Code ]********************************
' File...... SHT11.bas
' Purpose... SHT11 digital humidity sensor sample code
' MCU....... Microchip PIC16F877
' Software.. Converted to Proton+ 2.0 from PBPro ver 2.4
' Author.... Brandon Tarr
' E-Mail.... [email protected]
' Web....... http://www.spectrumedix.com
' Started... May 15, 2002
' Updated...
' Version... 1.0
'************************************************* *************************

'device 16f884a

DEFINE xtal 4
Define LCD_DREG PORTD
Define LCD_DBIT 4
Define LCD_RSREG PORTE
Define LCD_RSBIT 0
Define LCD_EREG PORTE
Define LCD_EBIT 1

TEMP con 1
HUMI con 2
' adr command r/w
Symbol statusregw = $06 ' 000 0011 0
Symbol statusregr = $07 ' 000 0011 1
Symbol measuretemp = $03 ' 000 0001 1
Symbol measurehumi = $05 ' 000 0010 1
Symbol resett = $1e ' 000 1111 0

' -----[ Variables ]---------------------------------------------------------------------
ledPin             var     PORTB.0
ledVar var byte

rxPin              var     PORTB.3
txPin              var     PORTB.2
SCK var PORTA.4 ' SHT11 SCK
SDATA var PORTB.1 ' SHT11 DATA

i  var byte
f var byte
value var byte
errorr var bit
mode var byte
ack var bit

vall var byte
pktvalue var word
pktchksum var byte

humival var word
tempval var word
dewpoint var byte
checksum var byte

' -----[ Initialization ]----------------------------------------------------------------
'ADCON1 = 7 ' Set PORTA and PORTE to digital
'Low PORTE.2 ' LCD R/W line low (W)
Pause 500 ' Wait for LCD to start
'lcdout $fe, 1

' -----[ Main Code ]---------------------------------------------------------------------
usetheSHT11:
    SerOut2 txPin, 16468, [" ", 10, 13]
    High ledPin          ' Turn on LED connected to PORTB.0
    Pause 500       ' Delay for .5 seconds
    Low ledPin           ' Turn off LED connected to PORTB.0

    gosub connectionreset
    value = measurehumi
    gosub measure ' measure humidity
    humival = pktvalue * 1000
    humival = DIV32 4095
    'lcdout $fe, 2, " ", $fe, 2, "Humidity: ", dec humival / 10, ".", dec humival // 10, "%"
    value = measuretemp
    gosub measure ' measure temperature
    tempval = pktvalue * 1000
    tempval = DIV32 16383
    'lcdout $fe, $c0, " ", $fe, $c0, "Temperature: ", dec tempval / 10, ".", dec tempval // 10, 223, "C"
    SerOut2 txPin, 16468, ["humival  ", DEC humival, 10, 13]
    SerOut2 txPin, 16468, ["tempval  ", DEC tempval, 10, 13]

    pause 500 '100 decrease sample time
goto usetheSHT11

' -----[ Subroutines ]-------------------------------------------------------------------
connectionreset:
' communication reset: DATA line is high and at least 9 SCK cycles followed by transstart
' ________________________________________ _____
' SDATA: |_____|
' _ _ _ _ _ _ _ _ _ __ __
' SCK: _| |_| |_| |_| |_| |_| |_| |_| |_| |___| |__| |___
    input SDATA
    high SDATA
    low SCK ' set initial state
    for i = 1 to 9 ' 9 SCK cycles
    high SCK
    low SCK
    next
    gosub transstart ' transmission start
return

transstart:
' generates a transmission start
' ___ _____
' SDATA: |_____|
' __ __
' SCK: __| |__| |___

    high SDATA
    low SCK ' set initial state
    high SCK
    low SDATA
    low SCK
    high SCK
    high SDATA
    low SCK
return

measure:
' makes a measurement (humidity/temperature) with checksum
    errorr = 0
    gosub transstart ' transmission start
    gosub writebyte
    for i = 1 to 255 ' wait until sensor has finished the measurement
        if SDATA = 0 then
            goto meascomplete
    endif
    pause 1
    next
meascomplete:
    if SDATA != 0 then ' or timeout (~2 sec.) is reached
        errorr = 1
    endif
    ack = 1
    gosub readbyte ' read the first byte (MSB)
    pktvalue.highbyte = vall
    gosub readbyte ' read the second byte (LSB)
    pktvalue.lowbyte = vall
    ack = 0
    gosub readbyte ' read checksum (no acknowledge to put sensor in "sleep" mode)
    pktchksum = vall
return

writebyte:
    ' writes a byte on the Sensibus and checks the acknowledge
    errorr = 0
    i = $80
    while i > 0
        if (i & value) != 0 then ' masking value with i
            high SDATA ' write to SENSI-BUS
        else
            low SDATA
        endif
        high SCK ' clk for SENSI-BUS
        low SCK
        i = i / 2 ' shift bit for masking
    wend
    high SDATA
    TRISB.1 = 1 ' release SDATA-line
    high SCK ' clk #9 for ack
    errorr = SDATA ' check ack (SDATA will be pulled down by SHTXX)
    low SCK
return

readbyte:
' reads a byte from the Sensibus and gives an acknowledge in case of "ack=1"
    vall = 0
    high SDATA
    TRISB.1 = 1 ' release SDATA-line
    i = $80
    while i > 0
        high SCK ' clk for SENSI-BUS
        if SDATA = 1 then ' read bit
            vall = vall | i
        endif
        low SCK
        i = i / 2
    wend
    TRISB.1 = 0 ' grab SDATA-line
    SDATA = ack ' in case of "ack", pull down DATA-Line
    high SCK ' clk #9 for ack
    low SCK
    high SDATA
    TRISB.1 = 1 ' release SDATA-line
return

softreset:
' resets the sensor by a softreset
    errorr = 0
    GOSUB connectionreset ' reset communication
    value = resett
    gosub writebyte ' send RESET-command to sensor
return

**tonyfelloni** · - 13th August 2008, 03:22

Hmmmm. This was a valid interesting topic.... pity it ends in the middle of nowhere without a solution!

skimask · - 13th August 2008, 04:03

Originally Posted by tonyfelloni

Hmmmm. This was a valid interesting topic.... pity it ends in the middle of nowhere without a solution!

I think there are a couple of other working examples somewhere here on the forums.
And heck, if the original poster doesn't care if the problem is solved, why should anyone else?

**tonyfelloni** · - 14th August 2008, 00:42

Hey Skimask

I care because its relevant to something I am working on now.... To find the perfect thread....only to discover you have been led up the garden path, haha. Not to worry, I did see a few other relevant posts elsewhere.

Cheers
Tony

View Poll Results: Have I included enough relevant material to make the problem clear?

Thread: Sensirion SHT11 with a PIC16F628-20

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Sensirion SHT11 with a PIC16F628-20

Compile Error with PBCP

Code looks the same

Re: Code looks the same

Got the E-mail

THANKS!

Need help also

Missing part of code SHT11

Please help me ??????

Sometimes I feel tired ... but why ????

sht11 vs. 16f84A

sht11 v 16f84a follow up

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