framistats.com

I just have a thing about getting new serial bus sensors that I don’t have code for. This week it is the SHT11 humidity/temperature sensor. This is also sold at mouser, as a parallax add on kit, 28018. The datasheets are here and here. There are sample files for a BASIC stamp, but that’s no use to me.

CODE

int shtClk=11;  // clock pin
int shtData=10;   // Data pin
int ioByte;
int ackBit;
unsigned int retVal;               // Return value from SHT11
int dly;
uint8_t bitmask;

void SHT_Write_Byte(void) {
  pinMode(shtData, OUTPUT);
  shiftOut(shtData, shtClk, MSBFIRST, ioByte);
  pinMode(shtData, INPUT);
  digitalWrite(shtData, LOW);
  digitalWrite(shtClk, LOW);
  digitalWrite(shtClk, HIGH);
  ackBit = digitalRead(shtData);
  digitalWrite(shtClk, LOW);
}

int shiftIn(void) {
  int cwt;
  cwt=0;
  bitmask=128;
  while (bitmask >= 1) {
    digitalWrite(shtClk, HIGH);
    cwt = cwt + bitmask * digitalRead(shtData);
    digitalWrite(shtClk, LOW);
    bitmask=bitmask/2;
  }
  return(cwt);
}

void SHT_Read_Byte(void) {
  ioByte = shiftIn();
  digitalWrite(shtData, ackBit);
  pinMode(shtData, OUTPUT);
  digitalWrite(shtClk, HIGH);
  digitalWrite(shtClk, LOW);
  pinMode(shtData, INPUT);
  digitalWrite(shtData, LOW);
}

void SHT_Connection_Reset(void) {
  shiftOut(shtData, shtClk, LSBFIRST, 255);
  shiftOut(shtData, shtClk, LSBFIRST, 255);
}

void SHT_Soft_Reset(void) {
  SHT_Connection_Reset();
  ioByte = 30;
  ackBit = 1;
  SHT_Write_Byte();
  delay(15);
}

void SHT_Wait(void) {
  delay(5);
  dly = 0;
  while (dly < 600) {
    if (digitalRead(shtData) == 0) dly=2600;
    delay(1);
    dly=dly+1;
  }
}

void SHT_Start(void) {
  digitalWrite(shtData, HIGH);
  pinMode(shtData, OUTPUT);
  digitalWrite(shtClk, HIGH);
  digitalWrite(shtData, LOW);
  digitalWrite(shtClk, LOW);
  digitalWrite(shtClk, HIGH);
  digitalWrite(shtData, HIGH);
  digitalWrite(shtClk, LOW);
}

void SHT_Measure(int vSvc) {
  SHT_Soft_Reset();
  SHT_Start();
  ioByte = vSvc;
  digitalWrite(11, HIGH);
  digitalWrite(11, LOW);
  SHT_Write_Byte();
  SHT_Wait();
  ackBit = 0;
  SHT_Read_Byte();
  int msby;
  msby = ioByte;
  ackBit = 1;
  SHT_Read_Byte();
  retVal = msby;
  retVal = retVal * 0x100;
  retVal = retVal + ioByte;
  if (retVal <= 0) retVal = 1;
}

int SHT_Get_Status(void) {
  SHT_Soft_Reset();
  SHT_Start();
  ioByte = 7;
  SHT_Write_Byte();
  SHT_Wait();
  ackBit = 1;
  SHT_Read_Byte();
  return(ioByte);
}

void SHT_Heater(void) {
  SHT_Soft_Reset();
  SHT_Start();
  ioByte = 6;
  SHT_Write_Byte();
  ioByte = 4;
  SHT_Write_Byte();
  ackBit = 1;
  SHT_Read_Byte();
  delay(1000);
  SHT_Soft_Reset();
  SHT_Start();
  ioByte = 6;
  SHT_Write_Byte();
  ioByte = 0;
  SHT_Write_Byte();
  ackBit = 1;
  SHT_Read_Byte();
}