diff --git a/ESPMegaPRO-firmware/lib/ESPMegaPRO/ESPMegaPRO_OOP.hpp b/ESPMegaPRO-firmware/lib/ESPMegaPRO/ESPMegaPRO_OOP.hpp
index 318da1f..31e3348 100644
--- a/ESPMegaPRO-firmware/lib/ESPMegaPRO/ESPMegaPRO_OOP.hpp
+++ b/ESPMegaPRO-firmware/lib/ESPMegaPRO/ESPMegaPRO_OOP.hpp
@@ -51,7 +51,17 @@ class ESPMegaPRO {
         void setTime(int hours, int minutes, int seconds, int day, int month, int year);
         ExpansionCard* getCard(uint8_t slot);
         FRAM fram;
+        /**
+         * @brief The Digital Input Card Built-in to the ESPMegaPRO board.
+         * @typedef DigitalInputCard
+         * @note This card is installed by default at slot 0 on the ESPMegaPRO R3 board.
+         */
         DigitalInputCard inputs = DigitalInputCard(INPUT_BANK_A_ADDRESS, INPUT_BANK_B_ADDRESS);
+        /**
+         * @brief The Digital Output Card Built-in to the ESPMegaPRO board.
+         * @typedef DigitalOutputCard
+         * @note This card is installed by default at slot 1 on the ESPMegaPRO R3 board.
+         */
         DigitalOutputCard outputs = DigitalOutputCard(PWM_BANK_ADDRESS);
         InternalDisplay *display;
         ESPMegaIoT *iot;