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[[https://www.thingiverse.com/thing:2609619|LEGO DUPLO train Flatcar Heavy hauler Schnabel car]]
Digital Analogue UART I2C Pin 1 D0 i/o A0 ip RX Clock Pin 2 D1 i/o A1 ip TX Data Pin 3 […]
I have a couple of these ESP8266 boards
[[https://www.thingiverse.com/thing:2479704|thing]]