Unable to upload schetch

[ionciubotaru]

I am using arduino IDE 1.8.1
I follow the instruction to download esp 32 from github and I run get.exe
I have a DEV board from olimex https://www.olimex.com/Products/IoT/ESP32-CoreBoard/
The board works on com30, I select ESP32 DEV Module,
When I put the board in programming mode I received on serial port:

ets Jun 8 2016 00:22:57
rst:0x1 (POWERON_RESET),boot:0x3 (DOWNLOAD_BOOT(UART0/UART1/SDIO_REI_REO_V2))
waiting for download

When I hit the upload button I received:

Sketch uses 385797 bytes (36%) of program storage space. Maximum is 1044464 bytes.
Global variables use 30348 bytes (10%) of dynamic memory, leaving 264564 bytes for local variables. Maximum is 294912 bytes.
esptool.py v2.0-dev
Connecting...

A fatal error occurred: Failed to connect to ESP32: Invalid head of packet ('a')
A fatal error occurred: Failed to connect to ESP32: Invalid head of packet ('a')

Please help

[me-no-dev]

try lower upload speed and hold the boot button while it's trying to upload the firmware

[copercini]

compile your sketch, and press and hold for few seconds the ESP flash button after arduino say the message in white:
Sketch uses X bytes (Y%) of program storage space. Maximum is Z bytes

Also, you don't need to put the board in programming mode.

[ionciubotaru]

Thank you, I succed keeping GPIO0 low during upload.