RTC RAM size...

[jedie]

I wanted to check the size of the RTC RAM, and hacked this:

Code: Select all

import machine

rtc = machine.RTC()
i = 1
while True:
    try:
        rtc.memory(b'X' * i)
    except Exception as e:
        print('Error:', e)
        print(len(rtc.memory()), 'Bytes')
        print(rtc.memory())
        break
    else:
        i += 1

Output on one of my ESP8266 boards:

Code: Select all

Error: buffer too long
492 Bytes
b'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'

Do all ESP8266 boards have the same size?

[shaoziyang]

In ESP32, rtc.memory() size is 2048.

[jimmo]

Yes, this is true of the ESP8266, the board doesn't change this.

You can read the MicroPython implementation at ports/esp8266/machine_rtc.c In particular look at the MEM_ constants near the top.

There are 256 bytes of system data (64 blocks), and 512 bytes of user data (128 blocks). The first section of the user data is used by calibration data (delta=2, cal=1, magic=1 blocks) and then the length of the stored Python data (1 block). So that leaves 512-(2+1+1+1)*4 = 492 bytes.