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26 lines
2.0 KiB
Markdown
26 lines
2.0 KiB
Markdown
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# GPIO API usage in Peripheral Drivers
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When a peripheral driver initializes IOs, the general rule is to append necessary configurations onto the IO, instead of using any GPIO APIs that overwrite the current IO setting, such as `gpio_config`, `gpio_set_direction`, `gpio_set_pull_mode`.
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Use `gpio_pullup_en` and `gpio_pulldown_en` to enable the internal pull-up/pull-down resistors if necessary.
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Use `gpio_od_enable` to configure an output IO as open-drain mode if necessary.
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## Configure an IO as a peripheral signal output
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There is no need to enable the output for the IO explicitly, it is done internally in the following function calls.
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If the signal is routed through IO MUX to the pin, then only needs to call `gpio_iomux_out` to select the IO MUX function index.
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If the signal is routed through GPIO Matrix to the pin, then first call `gpio_func_sel` to let the pin use `PIN_FUNC_GPIO` function, follow by calling `esp_rom_gpio_connect_out_signal` to connect the signal.
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When a peripheral driver does de-initialization, to de-configure the pin as the peripheral signal output, a call to `gpio_output_disable` is enough. It will disconnect the signal internally.
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## Configure an IO as a peripheral signal input
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If the signal is routed through IO MUX to the pin, then call `gpio_iomux_out` to select the IO MUX function index, and also call `gpio_iomux_in` to direct the signal to IO MUX. Input will be enabled for the IO internally.
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If the signal is routed through GPIO Matrix to the pin, then first call `gpio_func_sel` to let the pin use `PIN_FUNC_GPIO` function, follow by calling `gpio_input_enable` and `esp_rom_gpio_connect_in_signal` to enable the input and connect the signal to the pin.
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When a peripheral driver does de-initialization, to de-configure the pin as the peripheral signal input, use `esp_rom_gpio_connect_in_signal` to connect the signal to CONST_ONE or CONST_ZERO, so that it is disconnected from the pin. It is not desired to call `gpio_input_disable`, because there might be other drivers still using this pin as an input.
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