I am new here and new with using Arduino. Anyway, I am using 12-Bit + Sign Temperature Sensor and Thermal Window Comparator with Two-Wire Interface (http://www.national.com/mpf/LM/LM92.html#Overview), Arduino Uno with Ethernet Shield with microSD slot attached.
First I wanted just read data from sensor and then show results on Serial monitor. With that I didn't have no problem. I think results are good. But then I wanted to save this data on microSD card via Ethernet Shield.
I used one of the example on Arduino home page wich shows how to log data from three analog sensors to an SD card using the SD library. When I run program and then I see, that temperature data are not right.
If anybody knows where is problem or problems please help me!
Here is code:
#include <SD.h>
#include <Wire.h>
const int chipSelect = 4;
int msb,lsb;
void setup()
{
Wire.begin();
Serial.begin(9600);
Serial.print("Initializing SD card...");
// make sure that the default chip select pin is set to
// output, even if you don't use it:
pinMode(10, OUTPUT);
// see if the card is present and can be initialized:
if (!SD.begin(chipSelect)) {
Serial.println("Card failed, or not present");
// don't do anything more:
return;
}
Serial.println("card initialized.");
}
void loop()
{
// make a string for assembling the data to log:
String dataString = "";
Wire.requestFrom(0x4b, 2);
while(Wire.available())
msb = Wire.receive();
lsb = Wire.receive();
float temp = (msb<<8|lsb);
int a =(temp*50)/6400;
dataString += String(a);
dataString += ",";
// open the file. note that only one file can be open at a time,
// so you have to close this one before opening another.
File dataFile = SD.open("datalog.txt", FILE_WRITE);
// if the file is available, write to it:
if (dataFile) {
dataFile.println(dataString);
dataFile.close();
// print to the serial port too:
Serial.print("temperature = ");
Serial.println(dataString);
}
// if the file isn't open, pop up an error:
else {
Serial.println("error opening datalog.txt");
}
delay(500);
}
You want to wait for TWO characters and then read them:
while(Wire.available() == 0)
/* WAITING FOR A CHARACTER */;
msb = Wire.receive();
while(Wire.available() == 0)
/* WAITING FOR A CHARACTER */;
lsb = Wire.receive();
or
while(Wire.available() < 2)
/* WAITING FOR TWO CHARACTERS */;
msb = Wire.receive();
lsb = Wire.receive();
First I would like to say thank you very much for your reply. I really don't know who to ask about it.
I tried like you suggest. I changed mine code with your suggestions. I tried both your suggestions but in both cases is the same result. On monitor serial I see output results 0. Why is that so??
The code is:
#include <SD.h>
#include <Wire.h>
int msb,lsb;
float tempt;
int a;
int dataString;
const int chipSelect = 4;
void setup()
{
Wire.begin();
Serial.begin(9600);
Serial.print("Initializing SD card...");
// make sure that the default chip select pin is set to
// output, even if you don't use it:
pinMode(10, OUTPUT);
// see if the card is present and can be initialized:
if (!SD.begin(chipSelect)) {
Serial.println("Card failed, or not present");
// don't do anything more:
return;
}
Serial.println("card initialized.");
}
void loop()
{
Wire.requestFrom(0x4b, 2);
while(Wire.available() == 0)
msb = Wire.receive();
while(Wire.available() == 0)
lsb = Wire.receive();
float temp = (msb<<8|lsb);
int a =(temp*50)/6400;
// make a string for assembling the data to log:
String dataString = "temperature= ";
// read three sensors and append to the string:
dataString += String(a);
dataString += "";
File dataFile = SD.open("datalog.txt", FILE_WRITE);
if (dataFile) {
dataFile.println(dataString);
dataFile.close();
// print to the serial port too:
Serial.println(dataString);
}
// if the file isn't open, pop up an error:
else {
Serial.println("error opening datalog.txt");
}
delay(500);
}
Please help me! I really want to solve this problem!
Sorry, I feel so ..... I am beginner with Arduino and I forget on this details. I repair code and is working great! It shows me the value in whole numbers, but I also want to see the decimal value. Is this because of function int??
Thanks a lot for your help and time! I appreciate your help!
I got the same shield, how did you get the SD lib to compile? Or which version do you use? Tried 2 versions and all i get is 'SD.h:26: error: expected class-name before '{' token'.
I used the second option proposed by Johnwasser. At the end it was only problem because I forget to add ";" at the end of the line. After that it works fine for me. Now I wanted to see also decimal value. I need to make some more studies about it.
I don't know much about your code, but I think you have problem in 26 line and maybe is "{" missing or is too much.
This should print out the temperature to three decimal places:
int temperature = msb<<8 | lsb;
// make a string for assembling the data to log:
String dataString = "temperature= ";
// read three sensors and append to the string:
dataString += String(temperature/128);
temperature %= 128; // Strip off the integer degrees
dataString += "."; // Decimal point
for (int i=0; i<3; i++)
{
temperature *= 10; // "shift" the number one digit to the left
dataString += "0" + (temperature/128); // Add that one digit to the string
temperature %= 128; // Strip off that digit
}
dataString += "";
to drejcek
I'm a student and I wanted to ask if you can publish the project of 'interface between LM92 and ARDUINO UNO board.
I ask this because my professor asked me this task.
If you do me this favor, I would be very grateful.
Thanks