Go Down

Topic: USB interface design (Read 269 times) previous topic - next topic

zenseidk

Hello all,

I'm currently working on a project that has a USB interface and the ESP32.
The USB chip is the FTDI FT232RL. I'm in doubt about how the USB interface handles 5/3.3V via the VBUS.

Lets say that I use a 5V device on one side, say a computer and connect that to the USB power on the pcb I'm making.
The VBUS is then connected to VCC (3.3V) on the PCB I'm making.

How does this work? I'm afraid that the PC might send 5V over VBUS, which ends up on VCC on the PCB, frying the ESP32.

I've attached my circuit .

BlindWolf

#1
Feb 12, 2020, 08:56 am Last Edit: Feb 12, 2020, 09:13 am by BlindWolf
Hi,

FT232 chip has a pin(which is VCCIO) to chose voltage levels of I/O pins. For choosing voltage, the sample circuit is available under "7.4 USB to MCU UART Interface" title of FT232 Datasheet. If you are going to use it with PC, VCC of USB is 5V and your microcontroller is operating in 3.3V, then tie 3.3V with VCCIO pin. If you have still doubt, which one to use. I have a design like below. R11 and  R21 are 0-ohm resistors like a piece of wire. Solder R11 for 5v or solder R21 for 3.3V. Here, Be careful not to solder both resistors at the same time :D

Regards

Good luck

By Furkan

Go Up