Control an RC Toy Car with Raspberry Pi Pico Outputs

To control an RC car, you need an RF transmitter of some sort. These are readily available from your favorite online and/or in-person retailer, and often such cars come with a transmitter anyway. Matthias Wandel, however, wondered if it would be possible to control such a car, operating in the 49MHz range, with a Raspberry Pi Pico sans traditional transmitter.

It sounds like a rather ridiculous idea on its face, but the highly inventive and knowledgeable Wandel actually got this to work by flipping an IO pin at just the right frequency. The experiment, as seen in the video below, begins with MW holding the standard transmitter near a scope to see what he could pick up.

After he was able to sense the signal on a scope, he then initiated a flurry of experimentation, measurement, and ChatGPT-assisted programming of the Pico’s PIO pins. This allowed him to produce a Python-and-Assembly routine that oscillates the output pin at just about the exact 49.86MHz rate needed for car control. This gives a control range of six to seven meters with just a short jumper acting as an antenna.

As he notes, it’s a rather dirty signal, which would never pass FCC regulations, but it's an entertaining experiment nonetheless. It’s impressive that MW was able to do this in such a hacked together way, but it’s also a good illustration of why we have things like FCC regulations to, in theory, keep the airwaves free to use, or at least logically allocated.