12-16-2017, 05:15 PM
If you connect a UART device, there is not really any autodetection for that in Linux. You can open the corresponding /dev/ttySx with minicom or some other terminal program for example and see if you get any communication back and forth. This only requires that you know what UART settings for speed, stop bits, parity etc your ESP module needs (e.g. 115200 8N1).
As for setting the GPIO levels, on the low level side you would have to reconfigure them in the devicetree if you need them set during boot up. There is also the default setting the pins have by the hardware (which is input with pull-up enabled if I remember correctly, check the user manual here...). After the pins are configured as UART pins, the UART hardware controls the levels and you can't really influence that behavior....
As for setting the GPIO levels, on the low level side you would have to reconfigure them in the devicetree if you need them set during boot up. There is also the default setting the pins have by the hardware (which is input with pull-up enabled if I remember correctly, check the user manual here...). After the pins are configured as UART pins, the UART hardware controls the levels and you can't really influence that behavior....
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