How to store 1 bit Boolean data into EEPROM and retrieve this 1 bit data?

Question

I am building a project where I have to store the digital state which is Boolean (either HIGH or LOW) of each I/O port such that after power off the state of I/O ports store in EEPROM and I can retrieve this I/O port's state after power on.

This is my code..

    #include <IRremote.h>
    #include <EEPROM.h>
    int EEPROMaddress = 0;
    int EEPROMaddress1 = 1;
    byte EEPROMbyte = EEPROM.read(EEPROMaddress);
    byte EEPROMbyte1 = EEPROM.read(EEPROMaddress1);
    int RECV_PIN = 11;
    int led = 10;//1FE50AF
    int led1 = 9;//1FED827 
    boolean previousState = bitRead(EEPROM.read(EEPROMaddress), led);
    boolean previousState1 = bitRead(EEPROM.read(EEPROMaddress1), led1);
    boolean state;
    boolean state1;
    IRrecv irrecv(RECV_PIN);
    decode_results results;
    void setup()
    {
      Serial.begin(9600);
      pinMode(10,OUTPUT);
      pinMode(9,OUTPUT);
      irrecv.enableIRIn();
    }
    void loop() {
      if (irrecv.decode(&results)) 
      {
        Serial.println(results.value, HEX);
        switch(results.value)
        {
           case 0x1FE50AF:
           if (previousState == LOW)
           {state = HIGH;
            digitalWrite(led,state);
           previousState=state;
           bitWrite(EEPROMbyte,led,state);
           EEPROM.update(EEPROMaddress,EEPROMbyte);
           delay(50);}
           else
           {state=LOW;
           digitalWrite(led,state);
           previousState=state;
           bitWrite(EEPROMbyte,led, state);
           EEPROM.update(EEPROMaddress,EEPROMbyte);
           delay(50);
           }
           break;
            case 0x1FED827:
           if (previousState1 == LOW)
           {state1=HIGH;
           digitalWrite(led1,state1);
           previousState1=state1;
           bitWrite(EEPROMbyte1,led1, state1);
           delay(50);}
           else
           {state1=LOW;
           digitalWrite(led1,state1);
           previousState1=state1;
           bitWrite(EEPROMbyte1,led1,state1);
           delay(50);}
           break;
}   
        irrecv.resume(); 
      }
}

Answer 1

Since this is Arduino SE I'm going to do this with the Arduino functions, there are other ways of course.

Write a bit to EEPROM:

byte EEPROMbyte = EEPROM.read(EEPROMaddress);
bitWrite(EEPROMbyte, pinBit, pinState);
EEPROM.update(EEPROMaddress, EEPROMbyte);

Read a bit from EEPROM:

boolean pinState = bitRead(EEPROM.read(EEPROMaddress), pinBit);

This is for updating/reading a single bit at a time as asked. If you need to read/write multiple bits at the same time(as I'd assume you are doing after power on) then it's more efficient(and less wear on the EEPROM in the case of the write) to do all the bits at once instead of one EEPROM read/write per bit.

I assume by "I/O ports" you mean Arduino pins. If you're working directly with the PORT registers(e.g. PORTB) then you can just write or read the whole register to the EEPROM, no need to deal with the individual bits.

Answer 2

Note that writing EEPROM is slow - on the order of milliseconds per write - which may limit the performance of your sketch.

A better technique is to provide a limited backup power supply to the MCU; enough to complete a set of EEPROM writes + a safety margin. A capacitor could possibly provide enough run time if doesn't have to power much else. Then, detect and interrupt on a failure of the main supply, immediately write your backup data to EEPROM, and enter an infinite loop to wait for the backup supply to fail. When the system resets, examine the EEPROM to be sure there is valid backup data there, restore what needs to be restored, and resume your task.

Update:

A search for "arduino backup power" finds a number of articles related to switching an Arduino from mains power to battery power when the mains fails. You would only need a very small battery if you're willing to only save necessary information then shut down until the power returns. A capacitor might keep your MCU running long enough to do that. Designing the circuit depends on too much we don't know about your system, though.

In fact, simply switching a backup battery as some of these articles describe, or better, running on a battery which is kept on a mains charger, may make a much simpler system that can surviVe reasonably long power outages without shutting down. Again, we don't know how often or how long your power goes out, and how reliable your system is required to be.

Answer 3

You can store any bits or bytes into eeprom in byte units. The eeprom itself doesn't care whether the data ISS bits or bytes or multi bytes.

Your code only needs to make sure that consistency is maintained in storying and retrieving of eeprom data.