Micro Sawppy Rover And Spektrum DX6i Radio Controller

There are a few missing features I I want in my Micro Sawppy Rover control board, but I’m going to leave them as to-do list items for a future revision. For now I will continue working with the version I have and solve more pressing problems. The top of the list: free this little rover from the constraints of a wired joystick.

There are many wireless control ideas on the table. I plan to adapt a version of the WiFi-based control scheme as I used for SGVHAk rover and Sawppy V1, simplified so it runs on an ESP32 instead of a Raspberry Pi. I am also interested in enabling Bluetooth control, with a main focus on BBC micro:bit and a secondary focus on Bluetooth-enabled Xbox controllers. And that’s not all! I want to add compatibility with classic radio control equipment, since that was a feature added by multiple Sawppy builders starting with Marco Walther (mw46d). I have some experience with WiFi and Bluetooth, so RC receiver is the novelty I wanted to try first.

When I met Marco and his Sawppy rover, I saw he controlled his rover using a large radio transmitter typical of remote control aircraft. In the past I had a few remote control aircraft with similar transmitters, and I also had several pistol-grip style transmitters for remote control cars. When I quit that hobby and gave away most of my equipment, that included old-school FM transmitters on the 72MHz (aircraft) and 75MHz (surface) bands. I kept only the latest hot technology of the time: Spektrum spread spectrum radios on the 2.4GHz band, one ground and one air.

My Spektrum RC aircraft controller was the DX6i which I bought as a transmitter-only unit without the usual bundled receiver and servo. At the time I only flew lightweight “Bind-N-Fly” aircraft that have their own integrated receiver tailored to the airframe for minimal weight. I thought if I ever needed a receiver I could buy one, which is still true but I didn’t want to spend that money unless I need to.

The first venue of investigation is whether someone has tackled teaching an ESP32 to speak Spektrum DSM2 or DSMX protocols directly, eliminating the need for a separate receiver module. They are all on the 2.4GHz band so the radio antenna and associated hardware might be compatible. But if anyone has done so, I failed to find their project. What I did find are multiple projects that used a Spektrum receiver module to handle RF duties and retrieving data over a serial link. Spektrum published an official reference document for this type of project, titled Specification for Spektrum Remote Receiver Interfacing: Enabling Use of Spektrum Remotes in Third-Party Products.

This might be an interesting project to tackle, but again I didn’t want to spend money right now to buy a compatible Spektrum remote receiver. Fortunately, I have another Spektrum transmitter, the DX3E, with a corresponding receiver.

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