ESP32-WROOM-32U - soldered - but not flashing

[obod0002]

Dear all,
I'v been using some of the different types of the ESP family - but the last one seems to not like me:

As I need low current, a deep sleep longer than 71minutes as well as an external antenna to increase range, I decided to buy two of the ESP32-WROOM-32U chips as well as the ESP-32S breakout boards.

I soldered both, checked to not soldered two side-by-side pins together and checked RESET button connects EN to GND as well as IO0 button connects GPIO0 to GND.

I'm using Arduino IDE and trying to upload a sketch that I was using together with a NodeMCU-32 development board.

I'm using a UART flasher that works fine with ESP-01, ESP-12 and even the development board of NodeMCU-32 (when not using that nice USB connection).

I'm connecting
ESP-32.....UART.......LiFePO4 (charged)
GND.........GND........GND
VCC..........................VCC
TX............RX
RX............TX
All other pins remain unconnected.

When the IDE is ready for upload, I'm holding down IO0 plus clicking RESET.
But it won't work, I'm always receiving the same error:
A fatal error occurred: Failed to connect to ESP32: Timed out waiting for packet header

Sure, my soldering skills on such tiny devices might be the reason, but I hope it's rather a difference between the various chips I missed out.

Thanks for helping
Olaf

[obod0002]

I found my mistake as I have to additionally connect
IO0 -> GND as well as
EN -> 3V3

Both soldered ESP32's accepted to be flashed. But currently only one is still working.
Maybe I put the other in a state where it's waiting for something different ...?

[obod0002]

sorry, me again.

I soldered to new ESP32's on breakout boards and something similar to what I described initially is happening again:
both boards flashed perfectly when I used it for the first time.
I connected four IO's in 'the upper right corner':
3v3 to +@LiFePO4
EN to +@LiFePO4
GND to LiFePO4 as well as GND@FTDI
TX to RX@FTDI
RX to TX@FTDI

(FTDI is 3V3 version. LiFePO4 is charged)

Now one of the two new boards is still flashing perfectly, the other one fails all the time.
Using the same FTDI, cables, LiFePO4, arduino ide, ...

What am I doing wrong?

[obod0002]

Hi,
Anyone out there who might have an idea or what I could check and how?
Every help is appreciated.

[chegewara]

https://github.com/espressif/esptool/wi ... -Selection

[obod0002]

meanwhile two are flashing but only if I switch between them. Using just one of the two working and flashing this one two consecutive times doesn't do ... hmmmm