Esp32 + Logic Level Converter + Custom PCB

[pabloglc]

Hi all,

I'm trying to connect ESP32-cam to my custom PCB (based on an nRF52832) with I2C. For that I need a Logic Level Converter, I have this one: Bi-Directional Logic Level Converter Hookup Guide - SparkFun Learn

These are my connections:
SDA/SCL (ESP32) --> LV1/LV2 (level shifter)
SDA/SCL (custom PCB) --> HV1/HV2 (level shifter)
3.3V --> LV (level shifter)
5V --> 5V(ESP32) and HV(level shifter)
common GND

If I reset the ESP32 without connecting 3.3V with the level shifter it works, but if LV is connected to 3.3V and I reset the ESP32 (turning off and on my custom PCB f.e), the ESP32 will reset all the time.

Maybe the connection is the problem?

[Idahowalker]

Could be.

[horace]

are you powering your custom PCB from the ESP-32-cam PCB?
if so you could be overloading the ESP power supply and causing it to reset

[pabloglc]

I have tried two set-ups, powering up the ESP-32 with the PCB with 5V, or powering the ESP-32 and PCB separately.

[horace]

which pins are you using for the esp32-CAM SDA and SCL?
note the camera is using SDA GPIO26 SCL GPIO27
sounds like you have a short circuit
if you disconnect the ESP SDA and SCL and connect the ground is it OK?

[pabloglc]

SDA is IO13 and SCL is IO12. I was curious you asked so I checked. If I disconnect IO12 (SCL) and reset ESP32 I don't have the problem of resetting. It's IO12 reserved o something?

[horace]

looked at various ESP32-cam pinouts and sample code and have not seen GPIO12 and GPIO13 mentioned as I2C pins
how-to-use-i2c-sensor-bme280-with-esp32cam uses pins 14 and 15
however, pins 12 and 13 may work as well
Edit: it appears that GPIO12 is bootstrap pin
don't have a ESP32-CAM at moment so cannot test

[pabloglc]

It seems to be the problem. Now it doesn't boot continuously. Thank you! I didn't find any reference to pin 12 being a bootstrap pin. What is exactly the purpose of that?

[horace]

none of the documentation appears to mention it
I found it here