Save byte value to nodemcu eeprom

Projects General Guidance
1

I am looking for a solution to save byte value to nodemcu eeprom when power loss
is there any code and circuit diagram?

2

NodeMCU has no EEPROM.

The EEPROM library, for ESP8266 boards, uses some Flash memory to emulate EEPROM.

You can add an external EEPROM chip to NodeMCU.

s-l400 (37)

Which do you need help with?

3

You need a power monitoring circuit to detect when the voltage level falls a given threshold level and then to interrupt the MCU for storing the critical data into EEPROM.

4

do you have circuit diagram & code to test?

5

Does you NodeMCU contain BOD (Brownout Detection) Circuit?

6

I just have nodemcu board

7

Just to clarify... are you ...

  1. Just wanting to know how to read/write to the EEPROM so data is retained after power loss?

OR

2). Wanting to detect power failure, and then write to the EEPROM at that point ?

8

yes

9

You may try the following simplified model (Fig-1) to save critical data into EEPROM when Vcc (3.3V) reaches at 2.58V during power failure. 2.58 V is the minimum voltage level at which NdeMCU keeps working.
NodeMCUAnalogCh
Figure-1:

1. Build circuit as per Fig-1.
2. Adjust the POT to get about 0.70 V (0.9/3.3*2.58) at A0-pin.
4. Upload the following sketch (untested):

#include <EEPROM.h>
float x = 13.67;

void setup()
{
  Serial.begin(9600);
  Serial.println();
  EEPROM.begin(512);
}

void loop()
{
  int y = analogRead(A0);
  if ((float)y <= 0.7)
  {
    EEPROM.put(0, x); //saving 13.67 into EEPROM
    EEPROM.commit();
    EEPROM.end();
    while(1);   //wait for evver
  }
  else
  {
    //do other tasks
  }
}
10

is it possible to write into esp8266 eeprom inside interrupt routine?

11

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