Si7021.gcb

#chip mega328p,16
#option explicit
#include <millis.h>       ' Include the Library
#define SAMPLERATE 4000     ' Flash rate in mS

#define hi2c_BAUD_RATE 100
#define hi2c_DATA PORTC.4
#define hi2c_CLOCK PORTC.5
hi2cMode Master

Dim Si7021_HighByte, Si7021_LowByte as byte
Dim SiRaw Alias Si7021_HighByte, Si7021_LowByte as Word

Dim Humidity,Temperature,TemperatureC,TemperatureF as Word
DIM Temperature as WORD

Dim Hundredths as Byte

#define USART_BAUD_RATE 9600
#define USART_TX_BLOCKING
#define USART_DELAY 10 ms


Dim CurMs, LstMs as word  ' declare working variables
' Main                    ' This loop runs over and over forever.
LstMs = 0
CurMs = 0

' Main                    ' This loop runs over and over forever.
Do
  CurMs = millis()

  if CurMs - LstMs >= SAMPLERATE then  ' required Time has Elapsed

    Read_Humidity
    Read_Temperature

    LstMs = CurMs                   ' And Record Toggle Time
  end if

Loop


Sub Read_Humidity
  Hi2CStart
  HI2cSend (0x80)  'Write
  Hi2cSend (0xF5)
  Hi2CReStart
  HI2CSend (0x81)  'read
  wait 50 ms   ' for conversion ( could be less)
  Hi2CReStart

  HI2CSend (0x81)  'read
  Hi2CReceive (Si7021_HighByte, ACK)
  Hi2CReceive (Si7021_Lowbyte, NACK)
  Hi2Cstop
  'now do the maths
  Humidity = (([long]SiRaw * 125) / 65536) -6

;  Locate 1,12
  If Humidity  < 10 then hserPrint "0"
  hserPrint "Humidity="+str(Humidity) : hserPrint "%"
  HSerPrintCRLF

End Sub

Sub Read_Temperature
  Hi2CStart
  HI2CSend (0x80)  'Write
  Hi2cSend (0xE0)

  Hi2CReStart
  HI2CSend (0x81)  'read
  Hi2CReceive (Si7021_HighByte, ACK)
  Hi2CReceive (Si7021_Lowbyte, NACK)
  Hi2Cstop
  wait 20 ms

  TemperatureC = (([long]SiRaw * 17572) / 65536) - 4685
  TemperatureF =   (([long]TemperatureC * 9) /5) + 3200

  Hundredths = TemperatureF % 100  'Modulud Divide
  TemperatureF = TemperatureF / 100

;  Locate 2,14
  hserPrint "Temp.="+str(TemperatureC) : hserPrint "." : hserPrint str(Hundredths)+" "

End Sub