Unstable EN voltage

[georgij]

Hi, I am a student working on a custom PCB with an ESP32-WROOM-32E module in a Project course.

I use FT232R as USB-UART bridge. I am having problems with EN pin dropping below the required voltage for chip to be turned on. I have changed capacitor value between EN and GND with no success.

Schematics: https://drive.google.com/file/d/1LMw0G- ... Y5YcX/view
NOTE: I only have Power Supply, Main MCU, USB to UART Bridge and Strapping Buttons connected. I don't have any Auto Programming circuitry.

Measurements with oscilloscope (Yellow: EN , Blue: 3V3):
https://cdn.discordapp.com/attachments/ ... nknown.png

I have changed PCB layouts and manufactured the PCB few times now and changed WROOM modules (I tried WROOM-32D and WROOM-32E) and the result is the same. Could anyone please help me understand why this is happening?

[Sprite]

Interesting. Nothing in your schematic looks wrong. Possibly it's something weird, like a cracked ceramic capacitor on C5?

[ZeroxCorbin]

Hello, have you gotten any resolution to this? I am experiencing the same thing.

[georgij]

Interesting. Nothing in your schematic looks wrong. Possibly it's something weird, like a cracked ceramic capacitor on C5?

I have several iterations of the same board with the same problem. It runs well for like 20 mins before EN fluctuates.

[georgij]

Hello, have you gotten any resolution to this? I am experiencing the same thing.

I ended up throwing out the design and using the ESP32-DevKitC-V4 with an external 3V3 regulator (I have desoldered the one on the DevKit). It works well. The problem with the new design is that whenever I have used the Adafruit's 20-pin 0.1" Female Headers as an adapter, it stopped working. I ended up removing the DevKit's unused pins (as an extra precaution) and soldering the remaining ones on the board. It works now, but I don't like this 'hack'.

Does not work with these headers: https://cdn.discordapp.com/attachments/ ... image0.jpg
This solution works: https://cdn.discordapp.com/attachments/ ... image0.jpg