Arduino DO sensor via Arduino Mega 2560 & ladyAda Datalogger

Projects General Guidance
1

Hello,
I need help adjusting the code so that I can

A) map 1023 to 0-255 scale
B) multiply the results of all the potentiometers by 0.68966
C) Record and Display in the serial monitor and datalog file on the datalogger

here it is: /*
SD card datalogger

The circuit:

  • analog sensors on analog ins 0, 1, and 2
  • SD card attached to SPI bus as follows:
    ** MOSI - pin 11
    ** MISO - pin 12
    ** CLK - pin 13
    ** CS - pin 4

*/

#include <SD.h>

// On the Ethernet Shield, CS is pin 4. Note that even if it's not
// used as the CS pin, the hardware CS pin (10 on most Arduino boards,
// 53 on the Mega) must be left as an output or the SD library
// functions will not work.
const int chipSelect = 10;

void setup()
{
// Open serial communications and wait for port to open:
Serial.begin(9600);
analogReference(INTERNAL1V1);
while (!Serial) {
; // wait for serial port to connect. Needed for Leonardo only
}

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(53, 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 = "";

// read three sensors and append to the string:
for (int analogPin = 0; analogPin < 3; analogPin++) {
int sensor = analogRead(analogPin);
dataString += String(sensor);
if (analogPin < 2) {
dataString += ",";
}
delay(500);
}

// 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.println(dataString);
}
// if the file isn't open, pop up an error:
else {
Serial.println("error opening datalog.txt");
}
}

Thank you

2

A) map 1023 to 0-255 scale

Otherwise known as divide by 4.

B) multiply the results of all the potentiometers by 0.68966

There is a handy * operator.

C) Record and Display in the serial monitor and datalog file on the datalogger

That code already does that (poorly). What help do you need?

3

how do I use the * operator with a string?

4

vmogli:
how do I use the * operator with a string?

A = 3*4 //This results with A=12

You may want to take some time and do a C tutorial. It will help you immensely when trying to code in C.

5

Thank you