Custom ESP32 board, unreliable boot

[thomasn]

Hi guys,

I am designing a board (..and learning as I go) based on ESP Wroom-32, which also contains a Sim800l module, a Max7219 driven LED display, Max485-based TTL to RS485 logic, and connectors to the outside world (two Serials, one used for programming and one for communication to another device) and to an energy meter.

My problem is that my ESP32 seemingly often doesn't boot when I power up. I cannot find any solid ways to reproduce, but it seems to worsen when I attach anything to my connectors (even if these aren't powered up).

I have attached my schematic and BOM. Is there anything I am missing, that needs to be added in order to make the ESP more reliable?

Any tips would be greatly appreciated!

[felmue]

Hello @thomasn

I was wondering if the 3.3 V regulator (which seems to be rated at 300 mA) is enough to power everything?

Also, have you considered a reset circuit instead of simply tying EN to VCC all the time?

Thanks
Felix

[becorey]

Missing bypass caps near the esp32, place 1uF and 100nF.
4V LDO MIC29302WU rated for 3A, should be more than enough.
LN1134 LDO 5V to VCC 3.3V, rated 300mA is insufficient, esp32 recommends 500mA and higher is a safe bet go for something rated 600-1000mA.
R16 is 470 Ohm from 4V to GND, seems like a waste of power there.
Need R 1K and C 1uF on esp32 EN, don't just tie directly to VCC.

Please read through the esp32 datasheet and hardware guidelines for lots of helpful information