Serial.begin and LCD initialization (+SHT11)

Forum 2005-2010 (read only) Software Interfacing
#1

I made a sketch for the SHT11 and dump the reading on a 16x2 LCD, and it works fine.
However I would also like to enable the possibility to read the same values from the USB/serial. But as soon as I add the Serial.begin() to the setup rutine the LCD refuse to initialize.
Am I overlooking some timing or what could be wrong?

#include <LCD4Bit.h> 
LCD4Bit lcd = LCD4Bit(2);   //create a 2-line display.
#include <stdlib.h>
#include <math.h>

/*
 * SHT11 to USB (Serial)
 * by Anders S. Nielsen
 *
 * An example of using the Arduino board to receive data from the 
 * Sensirion SHT11 humidity and temperature sensor. 
 * The Arduino board relays the data from the sensor to the USB port (serial port).
 * Based on code by http://dmgaming.com/
 *
 */

// Pin assignments
int shtClk=3; // SHT11 Clock pin is connected to this pin
int shtData=2; // SHT11 Data pin is connected to this pin
int boardLED=13; // A LED is connected to the pin (on Diecimila) and used to signal user
int baudrate=9600; // speed used for serial communication

// Misc variables
long logTime;
int adcCount;
int ioByte;
int ackBit;
unsigned int retVal; // Return value from SHT11
int dly;
long msTimer;
uint8_t bitmask;
double Temp; // changed from float to double
double Humi; // changed from float to double
double dewpoint;

// Calculation constants based on SHT11 data sheet
int   d1 = -40;     // from SHT11 data sheet @ 5V Vdd and Celcius operation
float d2 = 0.01;    // from SHT11 data sheet @ 14bit and Celcius operation
int   c1 = -4;      // from SHT11 data sheet @ 12bit operation
float c2 = 0.0405;  // from SHT11 data sheet @ 12bit operation
float c3 = -2.8E-6; // from SHT11 data sheet @ 12bit operation

// Function that writes a byte to the SHT11
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() 
{
  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);
}

// Function that reads a byte from the SHT11
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);
}

// Function that reset the SHT11
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);
}

// Function that reads data from the sensor
void SHT_Measure(int vSvc) 
{
  SHT_Soft_Reset();
  SHT_Start();
  ioByte = vSvc;
  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;
}

// This function can get the current status of the sensor
int SHT_Get_Status(void) 
{
  SHT_Soft_Reset();
  SHT_Start();
  ioByte = 7;
  SHT_Write_Byte();
  SHT_Wait();
  ackBit = 1;
  SHT_Read_Byte();
  return(ioByte);
}

// Heater function that can be used for sensor calibration
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(500);
  SHT_Soft_Reset();
  SHT_Start();
  ioByte = 6;
  SHT_Write_Byte();
  ioByte = 0;
  SHT_Write_Byte();
  ackBit = 1;
  SHT_Read_Byte();
}

//--------------------------------------------------------------------
double calc_dewpoint( double h,double t){
//--------------------------------------------------------------------
// calculates dew point
// input: humidity [%RH], temperature [[ch65533]C]
// output: dew point [[ch65533]C]
float k,dew_point; // local variables
k = (log10(h)-2)/0.4343 + (17.62*t)/(243.12+t);
dew_point = 243.12*k/(17.62-k);
return(dew_point);
}


void printInt(long n){
  byte buf[10];  // prints up to 10 digits  
  byte i=0;
  if(n==0)
    lcd.print('0');
  else{
    if(n < 0){
      lcd.print('-');
      n = -n;
    }
    while(n>0 && i <= 10){
      buf[i++] = n % 10;  // n % base
      n /= 10;   // n/= base
    }
    for(; i >0; i--)
      lcd.print((char) (buf[i-1] < 10 ? '0' + buf[i-1] : 'A' + buf[i-1] - 10));        
  }
}

void printDouble( double val, byte precision){
  // prints val with number of decimal places determine by precision
  // precision is a number from 0 to 6 indicating the desired decimial places
  // example: printDouble( 3.1415, 2); // prints 3.14 (two decimal places)

  printInt( (long)val);  //prints the int part
  if( precision > 0) {
    lcd.print('.'); // print the decimal point
    unsigned long frac;
    unsigned long mult = 1;
    byte padding = precision -1;
    while(precision--)
      mult *=10;       
    if(val >= 0)
      frac = (val - int(val)) * mult;
    else
      frac = (int(val)- val ) * mult;
    unsigned long frac1 = frac;
    while( frac1 /= 10 )
      padding--;
    while(  padding--)
      lcd.print('0');
    printInt(frac) ;
  }
}


void setup()
{
  //setup serial port
  Serial.begin(baudrate); // open serial
  
  // Initialize the LCD
  lcd.init();
  lcd.clear();

  //digitalWrite(boardLED, LOW);
  //delay(1000);
  lcd.cursorTo(1,0);
  delay(50);  

  // Initialize the SHT11
  lcd.printIn("Initialize SHT11");  
  pinMode(shtClk, OUTPUT); // Set pin as output
  digitalWrite(shtClk, HIGH); // Set pin high
  pinMode(shtData, OUTPUT);  // Set pin as output
  pinMode(boardLED, OUTPUT); // Set pin as output

  // Initialize the sensor
  lcd.printIn("Resetting SHT11");
  SHT_Connection_Reset(); // Reset the SHT11 sensor
  lcd.cursorTo(2,0);
  lcd.printIn("Reset done");

  digitalWrite(boardLED, HIGH); // Light the pin13 LED
  //delay(1000); // Wait for 1000 miliseconds
  lcd.cursorTo(2,0); // Move cursor to first space on second line
  lcd.printIn("Ready to start!");
  delay(1000);  // Wait for 1000 miliseconds
  digitalWrite(boardLED, LOW); // Turn pin13 LED off (we are ready)
  lcd.clear();  // Remove everything visible on the display
  lcd.cursorTo(1,0);
  lcd.printIn(" HumiTemp v0.2a");
  delay(3000);
  
}

void loop()
{
  msTimer=millis(); // load number of milliseconds since the Arduino board began running the current program into msTimer
  if (msTimer <= logTime) // if msTimer is lower than the the last time we checked the run time then we reset the logTime.
  {
    logTime = 0;
  }
  if (msTimer > (logTime + 1000)) // if program has been running in more that 5 sec then we fetch new readings from the sensor
  {
    logTime = millis(); // recored current program run time
    digitalWrite(boardLED, HIGH); // Light the pin13 LED
    SHT_Measure(3); // Get SHT11 temperature
    digitalWrite(boardLED, LOW); // Turn pin13 LED off
    Temp = d1+d2*retVal; // Temperature conversion according to SHT11 data sheet
    lcd.cursorTo(1,0); // Move LCD cursor to first space on first line
    lcd.printIn("T:"); // Preload LCD with text
    printDouble(Temp,1); // display temp in ascii on LCD
    lcd.print(223); // print degree character (223d = 11011111b = CFh)
    lcd.printIn("C "); // will be printed right after temperature (no need to calculate position)
    digitalWrite(boardLED, HIGH); // Light the pin13 LED
    SHT_Measure(5); // Get SHT11 humidity
    digitalWrite(boardLED, LOW); // Turn pin13 LED off
    Humi = c1+c2*retVal+c3*(retVal*retVal); // Humidity conversion according to SHT11 data sheet
    lcd.printIn("H:"); // Preload LCD with text
    printDouble(Humi,1); // display humi in ascii on LCD
    lcd.printIn("%RH "); // will be printed right after humidity (no need to calculate position)
    dewpoint = calc_dewpoint(Temp,Humi);
    lcd.cursorTo(2,0); // Move LCD cursor to first space on second line
    lcd.printIn("Dp:"); // 
    printDouble(dewpoint,1);
    lcd.print(223); // print degree character (223d = 11011111b = CFh)
    lcd.printIn("C "); // will be printed right after temperature (no need to calculate position)
  }
}

thanks in advance.

#2

spelle:

LCD4bit was written a while ago. There is the possibility that some subtle changes in the later Arduino code is causing this problem. There was a similar problem between the LiquidCrystal library and Arduino prior to v0018. Why don't you use Arduino v0018 and the version of the LiquidCrystal that comes with it and see if you have better luck.

Don

#3

Ok, followed the advice and now cut-n-pasted something new together using LiquidCrystal and SHT1x libraries (it is always interesting to change more than one variable at the time…).
However the Serial vs. LCD activity is still unresolved.
In below code the serial communication runs fine but the LCD is dead in the water. The LCD is initialized ok and the “Starting SHT11” is written to the display but as soon as the serial communicaton is loaded the LCD communication is wrecked somehow and nothing comes out of the lcd-commands in the loop().

Any suggestions would be appreciated.

#include <SHT1x.h>
#include <LiquidCrystal.h>

// Specify data and clock connections and instantiate SHT1x object
#define dataPin 2
#define clockPin 3

float temp_c;
float temp_f;
float humidity;
// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 0, 7, 8, 9, 10);  
SHT1x sht1x(dataPin, clockPin);
 
void setup()
{
  // set up the LCD's number of rows and columns: 
  lcd.begin(16, 2);
  lcd.print("Starting SHT11"); 
  lcd.setCursor(1,1);
  Serial.begin(9600); // Open serial connection to report values to host
  Serial.println("Starting up");
}
 
void loop()
{
  // Read values from the sensor
  temp_c = sht1x.readTemperatureC();
  //temp_f = sht1x.readTemperatureF();
  humidity = sht1x.readHumidity();

  // Print the values to the serial port
  Serial.print("Temperature: ");
  Serial.print(temp_c,1);
  Serial.print("C / ");
  Serial.print("Humidity: ");
  Serial.print(humidity,1);
  Serial.println("%");

  lcd.setCursor(0,1); // 2nd row display
  lcd.print("T:");
  lcd.print(temp_c,1);
  lcd.print(" H:");
  lcd.print(humidity,1);  
  lcd.print("%");
  
  //Wait before we fetch next sample
  delay(1000);
}
#4

LiquidCrystal lcd(12, 0, 7, 8, 9, 10);

It looks like you are using pin 0 for the LCD Enable, but pins 0 and 1 are used for serial communications. Try a different pin for the Enable line.

Don

#5

YES! :)

Like always, obvious when you realize the reason.

#6