ESP32-S3-WROOM-1U pin behaviour at/after reset

[Jonathan2892]

Hello,

I have a question about the pin behaviour of esp32-s3-wroom-1u. The Technical Reference of the esp32-s3 says that MTDO (GPIO40) pin is IE (input enabled) after reset, without any pull-ups or pull-downs.
Now I connected a 20k pull-down resistor on this pin, so it should be low at and after reset. Right?

I connected this pin to a small chip that controls the power. If the pin goes high the power is turned of.
Now every time I press the reset button the system shuts down. If I tie MTDO/GPIO40 to GND with a wire and press reset the system stays on.
It looks like the esp pulls MTDO/GPIO40 to high after reset button is released. Is this true? Is the technical reference wrong here or do I get it wrong?

Best
Jonathan

[ESP_LJH]

Could you show me your schematic? I may not understand well your connections.

[Jonathan2892]

Hey,
Sorry I forgot the schematic.

Bildschirm­foto 2023-03-28 um 14.29.22.png (226.94 KiB) Viewed 4677 times

best
jonathan

[ESP_LJH]

As I know, GPIO40 should not be high during power-up but I find this, please say if you enter into USB OTG mode?
https://www.espressif.com/sites/default ... ual_en.pdf
table 33-7

[Jonathan2892]

Hey,

this is interesting...I think I am not using USB OTG, at least not on purpose...
So I got some new pcb's with the esp32-s3-wroom-1u on it. Since I need the UART0-pins for other functions I thought I could use the USB interface for flashing the firmware and for JTAG debugging. Thus I only need the two USB pins and can use the JTAG and UART0 pins for other stuff.

I know, that if I want to flash firmware for the very first time via the USB-JTAG interface I need to put the esp32-s3 in download-mode. But if I press the RESET button, GPIO40 goes HIGH (checked this with an oscilloscope).
This behaviour occurs also when I try to upload firmware via USB-UART or try to get the efuse-summary (vscode-extension).

Is the USB-OTG mode active by default?

In production the firmware will be updated via OTA, but for first time flashing and as a backup I want to use the USB/JTAG interface. For that I do not need the USB-OTG or DFU, right?

best
Jonathan

[30.03.2023]Update1:
After burning EFUSE_DIS_USB_OTG_DOWNLOAD_MODE everything works like it should. Since the default state of the esp32-s3-wroom-1u module is that the pin is on high from factory settings, I think I have only the option to change some pins... Because even to burn this efuse I need to short GPIO40 down to GND.
Or do you see another option for production?

[Jonathan2892]

Hey,

I investigated a little further and found the following:

I have some never used befor esp32-s3-devkitC-1 v1.6 boards. They have the fuse DIS_USB_OTG_DOWNLOAD_MODE = True already burned by factory.
The newer esp32-s3-wroom modules have DIS_USB_OTG_DOWNLOAD_MODE = False by factory.

Is there any way to figure out, which esp32-s3-wroom versions has the DIS_USB_OTG_DOWNLOAD_MODE fuse burned by factory and which not?

Is DIS_USB_OTG_DOWNLOAD_MODE = False now the standard settings by factory?

Best
Jonathan