Failed to connect to ESP32: Invalid head of packet.('\x08')

[thiamugb]

hi all,
I am new users of Pycon LoPy i want to test my board.
I use pycon hello_world in C at this https://github.com/pycom/pycom-esp-idf.
when i flash then with eclipse i have a mistake saying .
"""""
Connecting.....................................................

A fatal error occurred: Failed to connect to ESP32: Invalid head of packet ('\x08')
make: *** [flash] Error 2
"""""
i don't know where is my problem.
I use mac os x.
Need help.
thanx

[nadvorvo]

Hi everyone,
I hope you can help in this matter.
Thanks a lot for writing back.
Regards, Vojtech

I am following this tutorial:
https://docs.pycom.io/updatefirmware/device/

expansion board: V3.1
GPy V1.2
I am downgrading to version GPy-1.20.2.r1.tar.gz

I do not connect a jumper cable or wire between G23 and GND (only for version 2.0)
LED blinks blue (GPy not in programing mode).

It fails with message:
pycom failed to connect to esp32 invalid head of packet (\x08)

[robert-hh]

@nadvorvo try to lower the speec.

[nadvorvo]

Hi @robert-hh, @Gijs
Thank you for your reply.

I have tested both 115200/57600 Baud. Result is same:

Thanks a lot for writing back.
Thank you in advance for your assistance.
Regards, Vojtech

[robert-hh]

@nadvorvo Can you get a REPL prompt if you connect with the board using screen or the like?

[nadvorvo]

Hi @robert-hh, @Gijs
Thank you for prompt reply. The GPy is normally working with ATOM (python REPL is ok).

Thank you in advance for your assistance.
Regards, Vojtech

[robert-hh]

@nadvorvo Did you terminate Atom with command-Q before uploading the firmware?

[nadvorvo]

Hi @robert-hh,
sure Atom was terminated (no other app using this COM port)

[nadvorvo]

Finally thanks to @robert-hh problem was identified:
even it is V3.1 expansion board it was necessary to force Bootloader mode by connecting P2 to GND + pushing Reset
then everything was ok

You can recognize being or not being in bootloader mode:
LED flashing in period aprox. 3 second ... not being in bootloader mode
LED off ... bootloader mode

Regards, Vojtech

[Theodor Kier]

@nadvorvo For anyone having the same issue today, this solved it for me too