This is a hobby-scale (Yak) Rover project for exploring cheap ways of building Mars ready exploration platforms.
... or it's just a little Arduino powered robot that runs around the floor of my garage.
Many are stubborn in pursuit of the path they have chosen, few in pursuit of the goal.
- Friedrich Nietzsche
You say that like it's a bad thing.
Primarily this is an exploration of whatever I find interesting in the embedded systems space. It's a chance to catch up on some education I've missed and learn some new technologies.
The development process is:
- Build something minimal but interesting.
- See where it breaks
- Goto 1.
As part of the Yak Rover project, Stubborn borrows and (hopefully) contributes to a larger effort to develop technology for an open-source Mars rover.
The flight control system framework that powers both the Rover and Ground is a bespoke C library providing capabilities that I deem necessary. Much of my focus has been on telemetry and debuggability of an increasingly sophisticated software stack. I mean, on Mars who is going plug into the Serial port and hit the reset button for you?
The Stubborn Rover itself today is a simple beast of easy to assemble off the shelf-components. This first iteration is based on the parts found in an Elegoo Most Complete Starter Kit with some minimal additions.
- Arduino Duo
- L293D Dual H-Bridge Motor Controller
- Shock Switch
- Powerboost 1000 / 3.7 V Battery
- RFM69 Transceiver
- Adafruit Mini Robot Chassis Kit
There is of course a mess of loose wires to round all this out.
The plan is to find the shortcomings from this simple setup and iterate.
To communicate with the Rover, a ground station is needed. This is built around:
- Raspberry Pi 4
- RFM69 Transceiver (identical to the Rover's)
The software stack is built around several sub-components organized as Unixy as possible. These components ideally handle a single task and are easily replacable as mission demands evolve.
This python script uses CircuitPython to interface with the rfm69 transceiver
hardware. It presents a unix domain socket on the system /var/stubborn/radio
which other processes can use to send and receive data over the radio.
Bytes written to the socket are sent directly over the radio (and hopefully received by the Rover).
Bytes recieved are sent to to the listening client.
Only a single client can connect at a time.
This C program is built on the same CiC stack as the rover and provides a high-level communication interface to the Rover.
Client connect to comsock over a unix domain socket (/var/stubborn/comsock)
and send commands to the rover such as:
FWD 255
The server will send this command to the Rover and display the result:
OK
Or in the event of an error:
ERR 3
The comsock service also receives telemetry data from the Rover. It's writen in two formats.
/var/stubborn/to is a tab-delimited data file in the format:
NOW=2403777634 UP=167495 LOOP=0 COM=1 RSSI=229 ERR=2
/var/stubborn/to.json is JSON formatted:
{"NOW": 1632030343, "UP": 19252, "LOOP": 0, "RSSI": 229, "COM": 2}
The Ground Data System is a user interface for the ground station that uses the underlying components to receive commands from the user and display telemetry about the Rover's operation.
It's written in Go in uses the tview library to present a fun terminal-based UI.
Automated testing is currently limited to CiC library code. See more here
Rather than rely on the Arduino IDE, scripts powered by arduino-cli are available. Wrapper scripts (Scripts-To-Rule-Them-All) is available)
Ground station services are managed using systemd. Unit files are for radio and comsock services.
gds can be run directly using go:
go run main.go
This may change as this component increases in complexity.