Unable to flash ESP32-WROOM-32D through UART

[aiq25]

Hi guys. I'm having a strange issue flashing an ESP32-WROOM-32D module using UART (using an CH340C but I have tried it with a CP2104 module as well with no luck).

Upon restart of the ESP32, it communicates data via UART, so I think it is working nominally and the TX and RX lines are working.

When I try to program by putting it into bootloader mode (hold IO0 LOW then doing a RESET), I get the "waiting for download" message from ESP32 but when I try to program, Arduino can never connect to the module.

I have this on a breakout board from Amazon with 22uF capacitor on the 3.3V on the module and a 100nF from EN (RESET) to GND.

Attached are the messages I get from the ESP32 module.

I have also tied IO2 externally with a 10kOhm resistor to ground.

Does anyone have any experience with this?

I have tried to use different baud rates as well but no luck connecting during the flash process.

I'm using the latest Arduino IDE with the latest ESP32 cores.

[UberBen]

I picked the NodeMCU-32S in the IDE.  To program, I hold the IO0 button from power up until flashing is done.  Letting go of the IO0 button caused it to fail.
I have this board: https://www.amazon.com/gp/product/B09J95SMG7

[aiq25]

I tried another board and it worked. I guess the first breakout board I was working with had some issue with the "RX" pin.

[mazurov]

Related - if anyone is struggling with automatic bootloader entry from non-esp-idf toolchain the correct timing is on the screenshots. Details here: https://owenduffy.net/blog/?p=21574