ESPP32 GW doesn't run when I2C connected

[Colomer_1978]

Hello,

In an ESP32 gateway board I try to connect an ADC converter MCP3426. SDA to GPIO4  and SCK to GPIO12. Both pins are free to use according to the pinout information.

I also connected both pins to a 4k7 resistor to 3V3 according to I2C bus definition.

When I have this connected, I try to program the ESP32 using the USB and I receive the error "A fatal error occurred: Timed out waiting for packet content
Failed uploading: uploading error: exit status 2"

If i turn it off and on, the ESP32 gives a continuous error  "12:36:59.007 -> invalid header: 0xffffffff"

I don't understand why this problem happens. Any idea? Thanks

[Colomer_1978]

Found the problem. Actually it's not related to I2C but to the pin I use, GPIO 12 must be LOW during boot and given that I2C pins are connected to +3V3 through the resistor, it wwas not LOW during the boot.

https://randomnerdtutorials.com/esp32-pinout-reference-gpios/

[LubOlimex]

Thanks for update. I was going to say to look in the bootstrap table, it is also visible in ESP32-GATEWAY schematic, bottom-right.