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Arduino MEGA (also ESP8266 NodeMcu, Wemos) have a much less compiled firmware and depends of ethernet controller type (ENC28J60,W5100,W5500 for AVR microcontrollers), Real-Time Clock device(DS1307, DS3231) or Serial only support. Each firmware has detailed info what type of I/O is supported. Arduino UNO and NANO have limited flash and RAM memory and because of that, there is a much more firmware for these devices with different configurations. The software send array of data, store data in EEPROM and decode at Arduino initialization according to uploaded firmware.
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ACC also have built in firmware uploader, so you don't need to have installed Arduino IDE.
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ACC package has already defined firmware (Arduino compiled sketch) with support for different types of the boards(AVR,ESP8266), sensors, ethernet(network) controllers, Real-Time clock(RTC) devices, timers and counters.
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