Implement gpio:init/1 on esp32

[pguyot]

Some GPIO pins require initialization as gpio pins to work, for example GPIO 4 on ESP32C3. This is achieved by calling esp-idf gpio_config. Implement this within gpio:init/1 which is used on rp2040.

These changes are made under both the "Apache 2.0" and the "GNU Lesser General
Public License 2.1 or later" license terms (dual license).

SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later

[UncleGrumpy]

Is there any documentation in ESP-IDF about which pins require this special use case? This is new to me, and I can’t find any reference to this being needed for certain pins. We definitely need clear documentation about which pins this is required for to enable them.

[UncleGrumpy]

This definitely hammers home the need to re-write our GPIO APIs so that they are unified across platforms (and now chipsets within platforms).

[pguyot]

Is there any documentation in ESP-IDF about which pins require this special use case? This is new to me, and I can’t find any reference to this being needed for certain pins. We definitely need clear documentation about which pins this is required for to enable them.

The documentation says:

Do not rely on the default configurations values in the Technical Reference Manual, because it may be changed in the bootloader or application startup code before app_main.

https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/peripherals/gpio.html

Because we didn't call gpio_config, we did rely on previous configuration.

Explicitely, the technical reference manual of esp32c3 (page 169) says that pin 9 of esp32-c3 has function 0 MTMS and function 1 GPIO4, so I'm not surprised I had to call gpio_config. There also are functions to select pin functions, but the API changed between esp idf versions, so I favored gpio_config in gpio:init/1.

https://www.espressif.com/sites/default/files/documentation/esp32-c3_technical_reference_manual_en.pdf

The table seems to document that gpios 4-7, 12-17 and 20-21 would need this. Not all are exposed on popular esp32c3 boards though.

[bettio]

Can we mention this change in our changelog?
Let's place this under v0.6.4 section (that I added just before).