Sensirion SHT11 with a PIC16F628-20

[Original]

Look at this:

'*******************************[ 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