I can't flash ESP32-WROOM module in my project

[thoraz]

I created a board with ESP32-WROOM module with the intent to program it through an external USB to UART dongle, but now I can't do it: Eclipse returns "A fatal error occurred: Failed to connect to ESP32: Timed out waiting for packet header". My schematic is the following



and the dongle is like this one



The signal TX0 on the module stay high (3.3V) while the RX0 seems to receive data. Are my connection in the schematic correct or I'm missing something?

[mikemoy]

your missing a button on the EN line to reset it after you pull GPIO0 low to put it into programming mode.
Your also missing a pullup on GPIO0. I believe there is a internal pullup but you'd have to check that.

[senudajayalath]

your missing a button on the EN line to reset

According to thie official datasheet you do not need a reset button right ?

[mikemoy]

You do not need a "button" but when flashing you need a way to pull EN low. His schematic has no provision for doing that.

[chegewara]

You do not need a "button" but when flashing you need a way to pull EN low. His schematic has no provision for doing that.

Actually you dont need to do it, its enough to pull down IO0 and then connect to power supply.

[mikemoy]

Actually you dont need to do it, its enough to pull down IO0 and then connect to power supply.

Sure, you can do it that way as well. But why bother when the EN and IO0 signals are built into the programming adapter. Just run the extra signal line. If your going to have a way to pull IO0 low, you might as well do the same for EN.

[Minatel]

Hi there!

Any progress on that?

It's quite important to keep signal LOW on GPIO0 during the BOOT process (after that you can release it to HIGH). Usually you have a auto program mode on most of development boards using two transistors on the serial DTR and RTS (see schematic below).

ESP_boot_circuit.png (10.59 KiB) Viewed 10243 times

If you don't have this circuit embedded on your development board, you can create using a simple push button.

[becorey]

Your schematic shows P_GND (39) not connected. That should be connected to ground.