Changed ESP8266-01 to wrong settings by mistake. It was working ok at 115200 (its default settings). It was connected like this:


Using Arduino as bridge

  • Pins 0 and 1 (RX/TX) connected directly to ESP8266 since I didnt have USB to TTL adapter.
  • MCU removed so I could make that scenario work

It was just for testing AT commands. I did it like that because I realized that I was getting errors all the time trying to connect using SerialSoftware (and different pins in Arduino).

Found out later that SerialSoftware does not work correctly at 115200...

So I issued the following AT command:


Now I cannot connect to the ESP8266 to correct that setting. All I get is garbage characters. I understand it's because of the flow control settings. I set it to both RTS and CTS which I also read later ESP8266 does not support?

Have tried:

  • Using Putty to change settings of COM port at connect. Have tried all speeps and flow control settings combinations I could think of. I get nothing or garbage characters.
  • Changing COM port setting from Device Manager (Windows 7)
  • Flashing ESP8266 using official tool (ESPFlashDownloadTool_v3.6.1.0).It won't sync with the ESP8266. It does not allow me to adjust speed to 9600. Minimun speed that show is 115200
  • Changing settings in ESPFlashDownloadTool_v3.6.1.0 so it will sync at 9600 (file: spi_download.conf)

I cannot think of anymore ideas. Have I completely messed up my ESP8266?

Is there a way that I'm not aware of that could fix this problem? How?

Thanks in advance!



2 Answers 2


Are you aware that this configuration (3) as a rule would require both RTS and CTS extra physical signals to work ? That means, if you do not connect anything there, the level present at some pin configured anywhere would prevent ESP8266 from receiving further data from serial.

In general people use "no flow control" (0)



As I stated in my post I did it by mistake. Nonetheless I was able to fix it by using a different flashing tool that used just one .bin file instead of many like the official ESP8266 tool does.

Can anyone please explain me why is that? Why are there different tools to flash the ESP8266? In concrete, why one requires just one file that will update the SDK and AT firmware in one pass, and the other requires many differente files? Or just a link to a site o post so I can better understand the differences?

The tool I ended up usign is "ESP8266 Flash Downloader"

enter image description here

The file I used: AiThinker_ESP8266_DIO_8M_8M_20160615_V1.5.4.bin


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