Small programs for controlling RC cars with HackRF.
This car works on 40.684 MHz and moves in 8 directions (forward, backward, left, right, forward-right, forward-left, backward-right, backward-left). You can see it in action here:
The remote control is using OOK modulation with long and short pulses. One long pulse is equal to three short pulses. For example, to move the car forward, we need to send 4 long pulses followed by 10 short pulses. We can easily find the control sequence for each direction by recording the signal from the RC and then analyse it with inspectrum:
To synthesize the signal with the HackRF, we need to transmit
SAMPLE_RATE/SYMBOL_RATE samples ('1' or '0') for each bit of the control
sequence. We can find the SYMBOL_RATE with inspectrum, it is about 2018.
We choose the SAMPLE_RATE to be 2M.
This is the Dickie Toys Flippy RC Car, it works on 2.4 GHz and moves in 6 directions. You can see it in action here:
First you need to turn on the car and then start fsk_car. This is because fsk_car sends a synchronization pattern upon start and the car needs to receive it.
You can find more details about the remote protcol in this blog post.
The programs depend only on SDL2, SDL2_image and libhackrf. To build on Linux:
$ sudo apt-get install libsdl2-dev libsdl2-image-dev libhackrf-dev
$ make
$ ./ook_car
$ ./fsk_car
To build on OSX:
$ brew install sdl2 sdl2_image hackrf
$ make
$ ./ook_car
$ ./fsk_car
If you want to support the project you can send me an RC toy and I will try to reverse engineer its protocol and add it here. Send me an email for more details.