For the transmitter, he turned an Arduino Pro Micro into a USB sound card which he could plug into his laptop. That outputs both the audio signal and a 40 kHz carrier signal, implemented using the ...

Humble's microcontroller ebook bundle shows you how to build wildly inventive projects with the popular Raspberry Pi and Arduino. By Alexandria Haslam Feb 22, 2019 8:06 am PST Image: Brad Chacos/IDG ...