Using EEPROM

Projects Programming
1

Hi, I've read multiple threads on different websites but I'm still a little stuck with this.

I am writing a program for an alarm, one of the functions allows the user to alter some values, based on the size of their fuel tank/fuel type. (tankw - width, tankl - length, weight - fuel density, warning - low level volume).

I want these values to be saved after setting, even if there is a power interruption, then loaded during the setup during restart.

Here is my function to update the values after the user goes through the function to set there values:

void setTank()
{
EEPROM.update(tankw,tankw); // write (tankw) to nonvolatile memory
EEPROM.update(tankl,tankl); // write (tankl) to nonvalatile memory
EEPROM.update(weight,weight); // write (weight) to nonvalatile memory
EEPROM.update(warning,warning);
}

and here is the code in my setup:

EEPROM.read(warning);
EEPROM.read(tankl);
EEPROM.read(tankw);
EEPROM.read(weight);

it compiles ok, I just don't think I have it right at the moment!

Any help would be appreciated, regards, Shaun

2 
 EEPROM.read(warning);
  EEPROM.read(tankl);
  EEPROM.read(tankw);
  EEPROM.read(weight);

You read the EEPROM but do not store the results.

Lokie so:

value = EEPROM.read(address);
3

thats what i thought was missing, loading the results to the correct place, thank you!

Would the update command save them OK?

4

Update is for saving (writing) values. To retrieve values, use read() or get().

5

shaunh84:
Hi, I've read multiple threads on different websites but I'm still a little stuck with this.

Have you read the EEPROM library documentation?

6

Why dont you serial print all your saved values so you can see exactly what is being stored and read

7

shaunh84:
Here is my function to update the values after the user goes through the function to set there values:

void setTank()

{
EEPROM.update(tankw,tankw); // write (tankw) to nonvolatile memory
EEPROM.update(tankl,tankl); // write (tankl) to nonvalatile memory
EEPROM.update(weight,weight); // write (weight) to nonvalatile memory
EEPROM.update(warning,warning);
}

This is not going to do what you expect it to. As is explained in the EEPROM library reference:
https://www.arduino.cc/en/Reference/EEPROMUpdate
the first parameter of EEPROM.update() is the EEPROM address. You need to define a specific address where each configuration is stored. Something like this:

unsigned int tankwAddress = 0;
unsigned int tanklAddress = 1;

... and so on

then:

EEPROM.update(tankwAddress, tankw); // write (tankw) to nonvolatile memory
EEPROM.update(tanklAddress, tankl); // write (tankl) to nonvolatile memory
8

Here is an example using put() and get() to store and save parameters in a struct. I used int data types in the struct but you can use any data type and even mix data types.

#include <EEPROM.h>

struct Config
{
   int height;
   int width;
   int weight;
   int alarm;
};

Config config;

void setup()
{
   Serial.begin(115200);

   // give elements values
   config.height = 150; 
   config.width = 100;
   config.weight = 40;
   config.alarm = 3;
   
   EEPROM.put(0, config);
   Serial.println("values written\n");
   
   Serial.println("retrieving values");
   EEPROM.get(0, config);
   Serial.print("height = ");
   Serial.print(config.height);
   Serial.print("   width = ");
   Serial.print(config.width);
   Serial.print("   weight = ");
   Serial.print(config.weight);
   Serial.print("   alarm = ");
   Serial.println(config.alarm);
   Serial.println();
}

void loop()
{

}
9

Thanks for the responses, I got there in the end, and until just now didn't know how to find old posts, and didnt realise there had been extra responses!

I used addresses to update and read from, had a little fun with numbers bigger than 255 but got there!