查了官網的資料後, 發現在 Arduino Nano 的 Getting started 文章中, 有以下的補充：
NOTE: We have updated the NANO board with a fresh bootloader. Boards sold from us from January 2018 have this new bootloader, while boards manufactured before that date have the old bootloader. First, make sure you have the Arduino AVR Core 1.16.21 or later looking at the Board Manager. Then, to program the NEW Arduino NANO boards you need to chose Processor > "ATmega328P". To program old boards you need to choose Processor > "ATmega328P (Old Bootloader)". If you get an error while uploading or you are not sure which bootloader you have, try each type of processor 328P until your board gets properly programmed.
也就是說, 2018 年 1 月開始, 官方售出的 Arduino Nano 控制板上方的 bootloader 是新版的, 所以 Arduino 1.8.6 預設是配合此新版的 bootloader, 如果是之前買到的 Arduino Nano 控制板, 在上傳程式時就必須選取『工具/處理器/ATmega328P (Old Bootloader)』選項, 才能正確上傳：
