Update gpio_example_main.c

Add comments to clarify how the bits of GPIO_OUTPUT_PIN_SEL and GPIO_INPUT_PIN_SEL are defined after the OR bit operator

Merges https://github.com/espressif/esp-idf/pull/10733

examples/peripherals/gpio/generic_gpio/main/gpio_example_main.c

@@ -38,9 +38,23 @@
 #define GPIO_OUTPUT_IO_0    CONFIG_GPIO_OUTPUT_0
 #define GPIO_OUTPUT_IO_1    CONFIG_GPIO_OUTPUT_1
 #define GPIO_OUTPUT_PIN_SEL  ((1ULL<<GPIO_OUTPUT_IO_0) | (1ULL<<GPIO_OUTPUT_IO_1))
+/*
+ * Let's say, GPIO_OUTPUT_IO_0=18, GPIO_OUTPUT_IO_1=19
+ * In binary representation,
+ * 1ULL<<GPIO_OUTPUT_IO_0 is equal to 0000000000000000000001000000000000000000 and
+ * 1ULL<<GPIO_OUTPUT_IO_1 is equal to 0000000000000000000010000000000000000000
+ * GPIO_OUTPUT_PIN_SEL                0000000000000000000011000000000000000000
+ * */
 #define GPIO_INPUT_IO_0     CONFIG_GPIO_INPUT_0
 #define GPIO_INPUT_IO_1     CONFIG_GPIO_INPUT_1
 #define GPIO_INPUT_PIN_SEL  ((1ULL<<GPIO_INPUT_IO_0) | (1ULL<<GPIO_INPUT_IO_1))
+/*
+ * Let's say, GPIO_INPUT_IO_0=4, GPIO_INPUT_IO_1=5
+ * In binary representation,
+ * 1ULL<<GPIO_INPUT_IO_0 is equal to 0000000000000000000000000000000000010000 and
+ * 1ULL<<GPIO_INPUT_IO_1 is equal to 0000000000000000000000000000000000100000
+ * GPIO_INPUT_PIN_SEL                0000000000000000000000000000000000110000
+ * */
 #define ESP_INTR_FLAG_DEFAULT 0
 
 static QueueHandle_t gpio_evt_queue = NULL;