Today I finally got two HM-10 modules. I did flash firmware using this tutorial. It worked until I didn't send AT+RENEW command. Now, LED blinks, I see device in BT terminal(Android phone) but I can't connect to it. Terminal says Connection failed: write descriptor failed. I tried sending commands over COM port from PC, but it doesn't responde. Also I connected pin 11 to GND, problem is still here. Strange thing - After firmware flash, AT+HELP doesn't exist, while AT+HELP? returns some website.

For second module, LED doesn't blink but I see module in BT terminal. It also stopped working after AT+RENEW. When I try to connect, I get same error.

  • it is unclear what you are doing ... the tutorial that you linked is NOT for flashing firmware to an HM-10 ... it is possible that you broke the device by flashing the firmware
    – jsotola
    Commented Sep 26, 2019 at 23:49

1 Answer 1


change your COM serial baud rate to 115200. I had the same problem and the moment I change the baud rate on my Serial Com or Serial monitor. it works for me

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