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Humidity and temperature: function for reading the RHT03 sensor (OshonSoft Basic).

DogFlu66

Member
Hello; this time I leave you the procedure to read the RHT03 humidity and temperature sensor.

It is a sensor that has a single-wire port, which is used to request the reading and also receive the reading from it.

All the lines of the function are commented and indicate the port reading procedure with their corresponding times.

Timer1 is used to convert the data frame generated by the sensor to bits. It is used to measure the width of the pulses that the RHT03 generates on its port.

The function has been tested working the microcontroller at 4 and 8MHz.

Function:
Call _Read_RHT03(HR, TMP, CHK, CLOCK, "C") 'Read sensor.
'Call _Read_RHT03(HR, TMP, CHK, CLOCK, "F") 'Read sensor.

HR: returns relative humidity.
TMP: returns temperature.
CHK: returns checksum = 0 = OK.
CLOCK: System MHz.
C or F: reading in ºC or ºF.

I leave the download link of the sensor data sheet.


LCD_RHT03.jpg


Code:
'**********************************************************************************
'Relative humidity and temperature reading function for the RHT03 sensor with TMR1.
'PicEBasic Board, By dogflu66, 03/2023.
'Basic Pic Simulator IDE (PSI), v6.92, Pic16F88.
'**********************************************************************************
Define CONF_WORD = 0x2f50
Define CONF_WORD_2 = 0x3ffc
Define CLOCK_FREQUENCY = 8
'Define SIMULATION_WAITMS_VALUE = 1  'Activate for simulation.
Define SINGLE_DECIMAL_PLACES = 1
'-----------------------------------------
'Include "_ProcSetUpEBasic.bas"
'Include "_FuncionesGeneralLibrary.bas"
'Include "_FuncionesPic16F88.bas"
'-----------------------------------------
'Clock internal.
OSCCON.SCS0 = 0
OSCCON.SCS1 = 0
'8Mhz
OSCCON.IRCF0 = 1
OSCCON.IRCF1 = 1
OSCCON.IRCF2 = 1
'4Mhz
'OSCCON.IRCF0 = 0
'OSCCON.IRCF1 = 1
'OSCCON.IRCF2 = 1
'Pin configuration
AllDigital
ConfigPin PORTA = Output
ConfigPin PORTB = Output
'Configuration lcd ports. --------------------------------------------
Define LCD_BITS = 4  'Data bus length to 4bits
Define LCD_DREG = PORTA  'Data bus: puerto A
Define LCD_DBIT = 0  'Least significant bit of the data bus.
Define LCD_RSREG = PORTB  'Rs control bit on port B
Define LCD_RSBIT = 7  'RS bit on RB7 pin.
Define LCD_EREG = PORTB  'E control bit on port B.
Define LCD_EBIT = 6  'E pin on RB6 pin
Define LCD_COMMANDUS = 2000  'Wait after each command in uSec.
Define LCD_DATAUS = 100  'Wait after sending a data to the LCD in uSec.
Define LCD_INITMS = 50  'Wait during display initialization in mSec.
'---------------------------------------------------------------------
Hseropen 4800  'Initialize port RS232
Lcdinit  'Initialize lcd
'-----------------------------------------
Lcdout "Test P. RHT03"  'Print text on lcd
Call _SetUp_RHT03()  'Initialize
Symbol _Led_RHT03 = RB1  'Pin is assigned to the RHTO3 adapter board led
ConfigPin _Led_RHT03 = Output  'Led

Dim CLOCK As Byte
CLOCK = 8  'System clock in Mhz
Dim HR As Single  'Relative Humidity
Dim TMP As Single  'Temperature
Dim CHK As Byte  'Checksum
 
WaitMs 2000  'Pause 2Sec.

While True  'Loop

    _Led_RHT03 = True
    Call _Read_RHT03(HR, TMP, CHK, CLOCK, "C")  'Read sensor.
    'Call _Read_RHT03(HR, TMP, CHK, CLOCK, "F")  'Read sensor.
    _Led_RHT03 = False
    Lcdcmdout LcdLine1Home  'Cursor to beginning of line1
    Lcdout "HR:", #HR, " T:", #TMP, "C "  'Data output on lcd (Europe)
    'Lcdout "HR:", #HR, " T:", #TMP, "F "  'Data output on lcd
    Lcdcmdout LcdLine2Home  'Cursor to beginning of line2
    Lcdout "Checksum: "  'Print checksum
    Select Case CHK
        Case 0
            Lcdout "OK.    "  'Reading ok
        Case Else
            Lcdout "ERROR. "  'Read error
    EndSelect

    WaitMs 500  'Pause in mSec.
Wend
End                                           
'Config pin datos port RHT03
Symbol _Pin_Data_RHT03 = RB4  'Assigns the data pin for the sensor RHT03
Symbol _Tmr1If = PIR1.TMR1IF  'Timer1 overflow indicator flag.
'Config pin as input and timer1
Proc _SetUp_RHT03()
    ConfigPin _Pin_Data_RHT03 = Input
    'Set timer 1
    T1CON = %00000000  'Assigns oscillator type (_Tmr1_Internal)
    T1CON.T1CKPS1 = 0  'Assign divisor x1
    T1CON.T1CKPS0 = 0
    T1CON.TMR1ON = 1  'Activate modulo
End Proc                                     
'****************************************************************************************************
'Rading function for the RHT03 sensor, returns values by reference of Relative Humidity,
'temperature and checksum.
'_HR: passes the velue for reference (relative humidity).
'_TMP: passes the value for reference (temperature).
'_CHK: pass the value by reference (checksum: = 1 errror, = 0 Ok).
'Input argument _CLK = Mhz of the system clock.
'_TMP = (_TMP * 9 / 5) + 32  'ºF
'_tmr1if = PIR1.TMR1IF  'Label the timer overflow flag.
'****************************************************************************************************
Proc _Read_RHT03(ByRef _HR As Single, ByRef _TMP As Single, ByRef _CHK As Byte, _CLK As Byte, _SYS As Byte)
    Dim _chk_aux As Byte
    Dim _HR03 As Word
    Dim _TMP03 As Word
    Dim _Signo As Bit
    Dim _n As Byte
    Dim _x As Byte
    Dim _v_aux(40) As Word
    'Initialization variables.
    _CLK = _CLK * 10  'calculates and assigns the duration of the pulse width corresponding
    _HR = 0
    _TMP = 0
    _chk_aux = 0
    _HR03 = 0
    _TMP03 = 0
    _Signo = 0
    _CHK = 1  'Checksum error is activated by defaul
    'Waits for the sensor communication port to become free.
    ConfigPin _Pin_Data_RHT03 = Input  'Sensor port as unput.
    Call _Clear_Timer1()    'Reset counter of timer1 and tmr1if.
    While _Pin_Data_RHT03 = False And _Tmr1If = False  'Wait until the port becomes free.
    Wend
    If _Tmr1If = True Then Exit  'No response, communication error.

    'MCU generates read start request to sensor (1 to 10mSec.)
    ConfigPin _Pin_Data_RHT03 = Output
    _Pin_Data_RHT03 = False
    WaitMs 5

    'MCU waits for the sensor to finish processing the read request (20 to 40uSec.).
    ConfigPin _Pin_Data_RHT03 = Input  'Port as read.
    Call _Clear_Timer1()    'Reset counter of timer1 and tmr1if.
    While _Pin_Data_RHT03 = True And _Tmr1If = False  'Waiting answer.
    Wend
    If _Tmr1If = True Then Exit  'No response, communication error.

    'MCU esperando que el sensor confirmte la petición de inicio de lectura (80uSeg.)
    Call _Clear_Timer1()    'Reset counter of timer1 and tmr1if.
    While _Pin_Data_RHT03 = False And _Tmr1If = False  'Waiting answer.
    Wend
    If _Tmr1If = True Then Exit  'No response, communication error.
 
    'MCU waiting for sensor to acknowledge read start request (80uSeg.)
    Call _Clear_Timer1()    'Reset counter of timer1 and tmr1if.
    While _Pin_Data_RHT03 = True And _Tmr1If = False  'Waiting answer.
    Wend
    If _Tmr1If = True Then Exit  'No response, communication error.

    'MCU Read datas en Bits (RH, TMP y Checksum), 26 a 28uSeg. = 0, 70uSeg. = 1
    _n = 0
    While _n < 40
        'Waiting for synchronization state to end to read the bit.
        Call _Clear_Timer1()    'Reset counter of timer1 and tmr1if.
        While _Pin_Data_RHT03 = False And _Tmr1If = False  'Waiting for synchronization state to end to raad the bit.
        Wend
        If _Tmr1If = True Then Exit  'No response, communication error.

        'Measuring the duration of the significant pulse of the bit
        Call _Clear_Timer1()    'Reset counter of timer1 and tmr1if.
        While _Pin_Data_RHT03 = True And _Tmr1If = False  'Measuring pulse duration.
        Wend
        If _Tmr1If = True Then Exit  'No response, communication error.

        _v_aux(_n) = _Get_Timer1()  'Assign timer counter.
        _n++  'Increments the index of the vector.
    Wend

    'Converts the captured times to bits.
    _n = 0
    While _n < 40
        Select Case _n
            Case <= 15  'Relative humidity.
                If _v_aux(_n) <= _CLK Then
                    _HR03 = _ClearBit32(_HR03, 15 - _n)
                Else
                    If _v_aux(_n) >= _CLK Then _HR03 = _SetBit32(_HR03, 15 - _n)
                Endif
            Case <= 31  'Temperatura ºC
                If _v_aux(_n) <= _CLK Then
                    _TMP03 = _ClearBit32(_TMP03, 31 - _n)
                Else
                    If _v_aux(_n) >= _CLK Then _TMP03 = _SetBit32(_TMP03, 31 - _n)
                Endif
            Case Else  'Received checksum
                If _v_aux(_n) <= _CLK Then
                    _CHK = _ClearBit32(_CHK, 39 - _n)
                Else
                    If _v_aux(_n) >= _CLK Then _CHK = _SetBit32(_CHK, 39 - _n)
                Endif
        EndSelect
        _n++
    Wend
    'Checks the received checksum with the computed checksum.
    _chk_aux = _HR03.HB + _HR03.LB + _TMP03.HB + _TMP03.LB  'Calculated Checksum.
    If _chk_aux <> _CHK Then  'If they are distinct.
        _HR = 0
        _TMP = 0
        _CHK = 1
    Else
        _CHK = 0  'Correct reading.
        _HR = _HR03 / 10  'Assigns decimal part.
        'Assign sign.
        If _TMP03.15 = 1 Then
            _TMP03.15 = 0
            _Signo = 1
        Endif
        _TMP = _TMP03 / 10  'Assigns decimal part.
        If _Signo = 1 Then _TMP = _TMP * -1  'Assigns sign.
        If _SYS = "F" Or _SYS = "f" Then _TMP = _TMP * 1.8 + 32  'ºF
    Endif
End Proc                                     
'**************************************************************************
'Returns value: Long
'Changes to 1 the value of a specified bit of a register up to Long.
'_reg: Is the unput variable or regiser, by value.
'_bit: Bit to modify, 0 to 31.
'_SetBit32: Image of the variable with the modified bit.
Function _SetBit32(_reg As Long, _bit As Byte) As Long
    If _bit > 31 Then _bit = 31
    _SetBit32 = 1
    _SetBit32 = ShiftLeft(_SetBit32, _bit)
    _SetBit32 = _reg Or _SetBit32
End Function                                 
'Returns value: Long
'Changes to 0 the value of a specified bit of a register up to Long.
'_reg: Is then unput variable or regiser, by value.
'_bit: Bit to modify, 0 to 31.
'_ClearBit32: Image of the variable with the modified bit.
Function _ClearBit32(_reg As Long, _bit As Byte) As Long
    If _bit > 31 Then _bit = 31
    _ClearBit32 = 1
    _ClearBit32 = ShiftLeft(_ClearBit32, _bit)
    _ClearBit32 = Not _ClearBit32
    _ClearBit32 = _reg And _ClearBit32
End Function                                 
'Returns counter of Tmr1
Function _Get_Timer1() As Word
        _Get_Timer1.HB = TMR1H  'Load the high byte.
        _Get_Timer1.LB = TMR1L  'Load the low byte.
End Function                                 
'Clear Tmr1 register and Tmr1If flag.
Proc _Clear_Timer1()
        TMR1H = 0  'clear high byte
        TMR1L = 0  'Clear low byte
        PIR1.TMR1IF = 0  'clear overflow Flag.
End Proc
 

Attachments

  • FunctionReadRHT03_TMR1.bas
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