ESP32C6 still resets with DTR when USB_SERIAL_JTAG_USB_UART_CHIP_RST_DIS is set

[clupien]

On windows, when the software disconnects from the serial port, it toggles the DTR line which resets the ESP32C6 (I have a esp32c6 devkit mini, v0.0).
I know there is nothing to do on the device for the USB to UART connection but on the USB Serial/JTAG, the documentations says:

Note that as described earlier, certain RTS/DTR sequences lead to hardware reset of ESP32-C6. Software can disable hardware recognition of these DTR/RTS sequences by setting the USB_SERIAL_JTAG_USB_UART_CHIP_RST_DIS bit, allowing software to interpret these signals freely.

This is in section 32.3.2 CDC-ACM Firmware Interface Functional Description of the ESP32-C6 Technical Reference Manual.

So I have been trying to change that bit but without any functional difference. Toggling the DTR signal still resets the ESP32C6.

The code I use is basically

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#include "soc/usb_serial_jtag_struct.h"
USB_SERIAL_JTAG.chip_rst.usb_uart_chip_rst_dis = 1;

which I used in the arduino devkit but also in the esp-idf. I even modified the 2nd stage bootloader to basically only do that and stop there and I still get the same behavior.

So has anybody been able to make that function work as documented or is this a hardware problem (or documentation error).

[ESP_Sprite]

You mean this development board? If so, make sure to connect to the 'USB' header; the other one is connected to an USB-serial chip.

[clupien]

Yes it is that device and I am using the correct connector.
Using pyserial under linux I can toggle the RTS/DTR lines and I can see the change on the device with the same register that contains the USB_SERIAL_JTAG_USB_UART_CHIP_RST_DIS bit. I also see that bit value change. I do the reading with something like:

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#include "soc/usb_serial_jtag_reg.h"
 printf("Chip RES_REG 0x%08x\n", *(unsigned int *)USB_SERIAL_JTAG_CHIP_RST_REG);

[ESP_Sprite]

One thing I can think of is that you need to write USB_SERIAL_JTAG_CONFIG_UPDATE to 1 to update the actual hardware.

[clupien]

Thanks a lot. That makes it work. So for other people that have the same problem the code is:

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#include "soc/usb_serial_jtag_struct.h"
USB_SERIAL_JTAG.chip_rst.usb_uart_chip_rst_dis = 1;
USB_SERIAL_JTAG.config_update.config_update = 1;

I might suggest a little more details in the documentation about the config_update register.
But otherwise I am happy. Thanks again.