Just followed a tutorial on how to set up ESP8266 with my Arduino Uno R3. I have a serial connection and get a response of the Arduino but I'm stuck now at chapter "first commands".

I have successfully issued the AT command and also the AT+RST command and got a response. BUT, the response return was "invalid" at its end instead of "ready". Also theres an output "MEM CHECK FAIL!!!"




 ets Jan  8 2013,rst cause:2, boot mode:(3,4)

load 0x40100000, len 1396, room 16 
tail 4
chksum 0x89
load 0x3ffe8000, len 776, room 4 
tail 4
chksum 0xe8
load 0x3ffe8308, len 540, room 4 
tail 8
chksum 0xc0
csum 0xc0

2nd boot version : 1.4(b1)
  SPI Speed      : 40MHz
  SPI Mode       : QIO
  SPI Flash Size & Map: 8Mbit(512KB+512KB)
jump to run user1 @ 1000

ÃÕMEM CHECK FAIL!!! <<----------------------------- ???
Ai-Thinker Technology Co. Ltd.

invalid <<----------------------------------------- should be "ready"

Can anyone explain me what that means? Do I have to (re)flash the firmware? And also - are the instructions all the same? I have bought mine from China but it was sold at the same ESP8266 module on Amazon.

  • The invalid on the end means that your config on the chip is either corrupted or not set up yet. So that's not part of your memcheck problem
    – Hyra Power
    Commented Jan 2, 2016 at 20:11

1 Answer 1



According to the tutorial it's an undocumented bug with no fix.

If you change the name, baud, and set up the wifi and password you should be good to go

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