Note: To use a pin as the GPIO, ensure that the E_IO_HV field is disabled in the corresponding pinmux register of the GPIO pin. You can disable the 3.3V Tolerance Enable field in the pinmux spreadsheet and reflash the board with the updated pinmux file.
Why should it not be possible to use a GPIO with 3.3V tolerance enabled? With an external pull-up, this should work. We have in our design GPIO22 and GPIO23, which we use as outputs with a pull-up to 3.3V.
I’m kind of interested in the answer to this myself. I think it is probably going to be due to the module itself operating at 1.8V, and then using a level converter on the carrier board to 3.3V. If the “tolerance” setting is for the module, then this would not be useful when it is the carrier board using the 3.3V. Any tolerance would be from the carrier board side unless it is a custom carrier board with a 1.8V passthrough. Not really sure though.
All the GPIOs on Thor SOC are 1.8V only and you will damage the Thor SOC GPIOs/pins if you are using 3.3V pull ups on some GPIOs. At the Jetson Thor Module level there are very few GPIOs which have a level shifter from 1.8V to 3.3V and hence the output at the module pin level is 3.3V CMOS. However, from Thor SOC perspective they are still 1.8V GPIOs and hence the E_IO_HV field in the pinmux needs to be disabled.
So why is there even an option to choose 3.3V tolerance for pins if they are not really 3.3V tolerant? What exactly happens then when E_IO_OD Open-Drain Select is enabled?
E_IO_OD field Enables or Disables OD feature in the GPIO so the GPIO can be used in OD mode. For example, E_IO_OD will be Enabled for I2C bus signals as both SDA and SCL are open drain signals. Even if you Enable E_IO_OD the external pull up needs to be 1.8V.
3V3 Tolerance Enable field is different and available on say AGX Orin , but not available for selection in Jetson Thor pinmux as all GPIOs are 1.8V only.