BMP180 LCD Problem

Hello,
This is my first Arduino project.
I have a Leonardo and a BMP180, with a 16x2 character LCD.
I have the BMP180 working, with sensible figures coming upon the serial monitor, but I get squiggly things coming up on the LCD (like the ‘divided by’ character and a little star wars figure).
I tried the ‘hello , world’ example and the LCD displays it perfectly.
I am trying to get it to display: ‘Press Temp’ on line 1 and
the measured values on line 2.
I can place a string of my choice in my setup area and it displays just fine, but, as soon as I put it in the Loop area, it goes wrong.
In desperation, I placed the print.lcd command in all sorts of places in the loop, but it didn’t seem to make a difference.
It’s as if the value is in non-printing characters, but it shows up OK in the serial monitor.

What am I doing wrong, please?

I have included my code below:

/* SFE_BMP180 library example sketch

This sketch shows how to use the SFE_BMP180 library to read the
Bosch BMP180 barometric pressure sensor.

Like most pressure sensors, the BMP180 measures absolute pressure.
This is the actual ambient pressure seen by the device, which will
vary with both altitude and weather.

Before taking a pressure reading you must take a temparture reading.
This is done with startTemperature() and getTemperature().
The result is in degrees C.

Once you have a temperature reading, you can take a pressure reading.
This is done with startPressure() and getPressure().
The result is in millibar (mb) aka hectopascals (hPa).

If you’ll be monitoring weather patterns, you will probably want to
remove the effects of altitude. This will produce readings that can
be compared to the published pressure readings from other locations.
To do this, use the sealevel() function. You will need to provide
the known altitude at which the pressure was measured.

If you want to measure altitude, you will need to know the pressure
at a baseline altitude. This can be average sealevel pressure, or
a previous pressure reading at your altitude, in which case
subsequent altitude readings will be + or - the initial baseline.
This is done with the altitude() function.

Hardware connections:

  • (GND) to GND
  • (VDD) to 3.3V

(WARNING: do not connect + to 5V or the sensor will be damaged!)

You will also need to connect the I2C pins (SCL and SDA) to your
Arduino. The pins are different on different Arduinos:

Any Arduino pins labeled: SDA SCL
Uno, Redboard, Pro: A4 A5
Mega2560, Due: 20 21
Leonardo: 2 3

Leave the IO (VDDIO) pin unconnected. This pin is for connecting
the BMP180 to systems with lower logic levels such as 1.8V

Have fun! -Your friends at SparkFun.

The SFE_BMP180 library uses floating-point equations developed by the
Weather Station Data Logger project: http://wmrx00.sourceforge.net/

Our example code uses the “beerware” license. You can do anything
you like with this code. No really, anything. If you find it useful,
buy me a beer someday.

V10 Mike Grusin, SparkFun Electronics 10/24/2013
*/

// Your sketch must #include this library, and the Wire library.
// (Wire is a standard library included with Arduino.):

#include <SFE_BMP180.h>
#include <Wire.h>
#include “LiquidCrystal.h”
// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

// You will need to create an SFE_BMP180 object, here called “pressure”:

SFE_BMP180 pressure;

#define ALTITUDE 1655.0 // Altitude of SparkFun’s HQ in Boulder, CO. in meters

void setup()
{
// set up the LCD’s number of columns and rows:
lcd.begin(16, 2);
// Print a message to the LCD.
lcd.setCursor(0, 0);
lcd.print(“Temp Press”);
Serial.begin(9600);
Serial.println(“REBOOT”);

// Initialize the sensor (it is important to get calibration values stored on the device).

if (pressure.begin())
Serial.println(“BMP180 init success”);
else
{
// Oops, something went wrong, this is usually a connection problem,
// see the comments at the top of this sketch for the proper connections.

Serial.println(“BMP180 init fail\n\n”);
while(1); // Pause forever.
}
}

void loop()
{
char status;
double T,P,p0,a;

// Loop here getting pressure readings every 10 seconds.

// If you want sea-level-compensated pressure, as used in weather reports,
// you will need to know the altitude at which your measurements are taken.
// We’re using a constant called ALTITUDE in this sketch:

Serial.println();
Serial.print(“provided altitude: “);
Serial.print(ALTITUDE,0);
Serial.print(” meters, “);
Serial.print(ALTITUDE*3.28084,0);
Serial.println(” feet”);

// If you want to measure altitude, and not pressure, you will instead need
// to provide a known baseline pressure. This is shown at the end of the sketch.

// You must first get a temperature measurement to perform a pressure reading.

// Start a temperature measurement:
// If request is successful, the number of ms to wait is returned.
// If request is unsuccessful, 0 is returned.

status = pressure.startTemperature();
if (status != 0)
{
// Wait for the measurement to complete:
delay(status);

// Retrieve the completed temperature measurement:
// Note that the measurement is stored in the variable T.
// Function returns 1 if successful, 0 if failure.

status = pressure.getTemperature(T);
if (status != 0)
{
// Print out the measurement:
Serial.print(“temperature: “);
Serial.print(T,2);
Serial.print(” deg C, “);
Serial.print((9.0/5.0)*T+32.0,2);
Serial.println(” deg F”);

// Start a pressure measurement:
// The parameter is the oversampling setting, from 0 to 3 (highest res, longest wait).
// If request is successful, the number of ms to wait is returned.
// If request is unsuccessful, 0 is returned.

status = pressure.startPressure(3);
if (status != 0)
{
// Wait for the measurement to complete:
delay(status);

// Retrieve the completed pressure measurement:
// Note that the measurement is stored in the variable P.
// Note also that the function requires the previous temperature measurement (T).
// (If temperature is stable, you can do one temperature measurement for a number of pressure measurements.)
// Function returns 1 if successful, 0 if failure.

status = pressure.getPressure(P,T);
if (status != 0)
{
// Print out the measurement:
Serial.print(“absolute pressure: “);
Serial.print(P,2);
Serial.print(” mb, “);
Serial.print(P*0.0295333727,2);
Serial.println(” inHg”);

// The pressure sensor returns abolute pressure, which varies with altitude.
// To remove the effects of altitude, use the sealevel function and your current altitude.
// This number is commonly used in weather reports.
// Parameters: P = absolute pressure in mb, ALTITUDE = current altitude in m.
// Result: p0 = sea-level compensated pressure in mb

p0 = pressure.sealevel(P,ALTITUDE); // we’re at 1655 meters (Boulder, CO)
Serial.print(“relative (sea-level) pressure: “);
Serial.print(p0,2);
Serial.print(” mb, “);
Serial.print(p0*0.0295333727,2);
Serial.println(” inHg”);

// On the other hand, if you want to determine your altitude from the pressure reading,
// use the altitude function along with a baseline pressure (sea-level or other).
// Parameters: P = absolute pressure in mb, p0 = baseline pressure in mb.
// Result: a = altitude in m.

a = pressure.altitude(P,p0);
Serial.print(“computed altitude: “);
Serial.print(a,0);
Serial.print(” meters, “);
Serial.print(a*3.28084,0);
Serial.println(” feet”);
}
else Serial.println(“error retrieving pressure measurement\n”);
}
else Serial.println(“error starting pressure measurement\n”);
}
else Serial.println(“error retrieving temperature measurement\n”);
}
else Serial.println(“error starting temperature measurement\n”);

delay(5000); // Pause for 5 seconds.
lcd.setCursor(0,1);
lcd.print(P);
}
<<<

Cheers,

John

Hi and welcome.

Please edit your post above and put your code in [code] [/code] tags.
Easiest way to do that is to highlight your code and then click the # button above the edit field.
Read this post (click !) so you can prevent annoying people you like to get help from.

You said you have tried the 'Hello World' sketch, did you check everything is the same ?
I mean did you check this line ?

LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

If the line in "Hello World' is different from the one you used in this other sketch, and 'Hello World' works, then you need to change the line in your own sketch accordingly.

You know, I'm having trouble with my LCD as well. It's a bit flaky. I have ( what appears to be ) a LCM1602C that came with the starter kit. I've wired it up correctly, done the tutorial and I'm able to send it text and display it, however, I have intermittent problems where it will fail to display a line, or show garbage, or replace one character with the wrong one, or append trash on the end of the line. I'm not sure if my problem is that my LiquidCrystal library is older or if I've got a bad part.

Hi Mithra

At this moment we can't be sure your problem is related to that of g4drs.
As you are describing your problem different from g4drs's problem, and in case you want help with that, ask your question in a separate thread.
That will prevent the possibility of people seeing your question as an attempt to hijack this thread, which is something you didn't plan to do of course.

I fixed it!
The Leonardo uses pins 2&3 for I2C and the standard 'Hello World' sketch uses those pins for the LCD.
I moved the LCD to some higher numbers and it all plays nicely!

Thanks, all for your advice.

John