ESP32 EN pin pulled down

[Devenda]

Hi,


Something strange is happening on my custom board featuring a ESP32-WROOM-32.
The EN pin is being pulled down (seemingly from the ESP32 itself), effectively preventing the ESP32 from booting.
This has not happened before and the board had functioned flawlessly in the past.

When tying EN directly to 3V3 (instead of using a pullup) the ESP32 boots and shows output on the serial bus.
When measuring EN <> GND for shorts (with a powered down board) it shows no connection (but had previously shown a short/low resistance).

Is it possible that the ESP32 pulls EN down (due to previously being damaged, a certain config setting the pin low,...)?

Strangely, another board had a similar issue with GPIO0, preventing flashing. After (destructively) removing the ESP32 and measuring the PCB (and ESP32) no shorts were found, I ruled this a broken ESP32-WROOM.

Other boards currently work fine.

Any pointers would be welcome, thanks in advance!

[WiFive]

viewtopic.php?f=12&t=11552

It is possible you had a short or whisker on your pcb and running 3.3v rail through it burned it out and fixed it.

[Devenda]

That's something I thought of too. But the problem persists. Strangely it worked fine before. The only thing I can think of is that something else went wrong, damaging the esp32 wroom internally, but again it boots fine, I'm just unable to program it again...

[vonnieda]

Do you have your power enable tied to your ESP enable, by chance?

I had a problem where I had power enable and ESP enable tied together. When the ESP is not powered fully, it will sink current on EN (and other signals). In my case, when I would turn on EN, as power started to come up the ESP would pull EN back down causing power to fail.

The solution in my case was to separate power and ESP enable, bring up power first, and then ESP enable a few ms later.

Jason

[Devenda]

Do you have your power enable tied to your ESP enable, by chance?

I had a problem where I had power enable and ESP enable tied together. When the ESP is not powered fully, it will sink current on EN (and other signals). In my case, when I would turn on EN, as power started to come up the ESP would pull EN back down causing power to fail.

The solution in my case was to separate power and ESP enable, bring up power first, and then ESP enable a few ms later.

Jason

Thanks for the hint, but the only things connected are the auto program transistor, a pull up and switch. Even without all those it still is being pulled down.

So the only other options are an internal issue in de esp wroom, or an issue on the PCB but I don't suspect the latter.

[ZeroxCorbin]

Hello, sorry to revive an old thread. I am having this same issue on a couple of custom boards. Did you ever resolve this issue?

Thank you for any advise.

[estratos]

I facing the same Issue on a ESP32 WROVER-1B CHIP ESP32-D0WD (revision 1)

Enable Pin eventualy goes low after a few minutes, what is funny that iron heating up the castellated solder joints again "removes" the short, after this I can flash the chip again with arduino IDE and with esptool without giving errors.
But chips keeps rebooting itself and eventuallly the Enable Pin shorts to ground about 2 kohm resistance to ground when you remove power.
Nothing of this make sense to me, if you left the chip power up and in download mode the enable pin stays HIGH indefinitely.

I dont think is a defective module, maybe the partition table and the fuses are mess up, at this point the only diferent thing I did before this happen, I was flashing and the program crashed my computer.

Any Clue?

[estratos]

What Chip part number are you using?, Mine is ESP32 WROVER IB on a custom board.
EN Pin is pulled up to a 10K resistor with a 1uf cap to ground, the GPIO0 Pin pulled up with a 10k resistor. To enter to flash mode as usual, EN pin short to ground then Boot Pin short to ground and release Boot after EN.

Captura de pantalla 2021-07-14 062756.png (7.59 KiB) Viewed 10950 times

Captura de pantalla 2021-07-14 062713.png (19.92 KiB) Viewed 10950 times

[smarq8]

today I face very similar issue for my custom board, it use ESP32-WROOM-32D. My board was running several hours sending some data over ESPNOW and at some point it restart few times and then was unable boot.
As I measure EN there was 160ohm to ground, after resoldering area it drop even more to around 40ohm and still not running. In the end I just short it for a while to 3V3 and it bring to 150Kohm and boot succesfully, its still way lower than other board i had (500K and 2,5M).
Any idea where is source problem?

PS. before I short it to VCC I also desolder any external component connected to EN except of 10kpullup to ensure its nothing on my board

[hegoku]

today I face very similar issue for my custom board, it use ESP32-WROOM-32D. My board was running several hours sending some data over ESPNOW and at some point it restart few times and then was unable boot.
As I measure EN there was 160ohm to ground, after resoldering area it drop even more to around 40ohm and still not running. In the end I just short it for a while to 3V3 and it bring to 150Kohm and boot succesfully, its still way lower than other board i had (500K and 2,5M).
Any idea where is source problem?

PS. before I short it to VCC I also desolder any external component connected to EN except of 10kpullup to ensure its nothing on my board

I have the same issue... The ESP32 shut down suddenly and then it can not restart. I measure the voltage of EN pin, it is 0V.
When I short the EN pin to GND, it restart again....
So confusing....