UART does not work when powering through VIN

[gfurtadoalmeida]

Hi,
I'm using 5 ADCs (32, 35, 34, VN, VP), 3 outputs (18, 19, 21) and UART2 (RX2, TX2).
The logic driving the ADCs and outputs works fine on VIN but I got nothing on the UART.
When powered through USB everything works fine.

I've tried (with no luck):
* UART0 and UART2.
* Connecting VIN to 9V.
* Disconnecting everything; powering only the board.
* Adding a 100uF capacitor between VIN and GND.

Is there any configuration I'm missing?
Has anyone faced this problem?

Hardware:
* Board: ESP32 DevKitC-V1 WROOM-32
* Core Installation version: v4.3-dev-907-g6c17e3a64-dirty
* IDE name: Visual Studio Code with ESP32 plugin
* Flash Frequency: 40Mhz
* PSRAM enabled: no
* Upload Speed: 115200
* Computer OS: Windows 10

Power Supply
* Generic wall adapter: 9V, 1A.
* Voltage regulator: LM8705CV, from 9V to 5V.

Measures taken on the AMS1117 (onboard power regulator):
* Input: 5.10V
* Output: 3.29V
* Current drawn: ~50mA

[ESP_Sprite]

Are you using the 'default' pins for UART0? One thing I can think of is that your devboard doesn't power the onboard USB-to-serial converter from Vin and as such that chip will permanently pull down these pins. You could try using alternative pins for the UART peripheral to check if this is the case.

[gfurtadoalmeida]

I've tried with the defaults one for both UART0 (rx0, tx0) and UART2 (rx2, tx2), neither worked.
Should it happen only to UART0 or both?

I'll let you know if changing to other pins works.

Thanks!

[gfurtadoalmeida]

It was sheer stupidity.
The FTDI board had its jumper set to 5V; setting to 3.3V solved the problem.
Being dumb is hard, kids.

It's interesting though that the board was able to deliver 5V while connected using USB.

Thanks everyone.