communications

TCP server/client(s): Base station -> multiple Arduino devices (over ethernet, via Raspi/Jetson node)

Sensors Attached to the SBC:

GPS (GlobalSat BU-353S4)
LIDAR (Slamtec RPLIDAR A1)
RealSense with Built-In IMU (D435i) (Not the D435)

Also Connected to the SBC:

Raspberry Pi running drive code and arm code

Notes / Scratchpad

Controller Data Acquisition

Python/Server Approach

https://inputs.readthedocs.io/en/latest/user/quickstart.html

This lacks a true front-end, so a shell of a front end would be required. The TCP server would have to be modified to send commands both over TCP and HTTP so that the browser can receive the data.

Client/Server Assignment

Definitions: Fail-Safe: Assume all controls are set to zero if connection drop; Fail-Unsafe: Assume all controls remain the same if connection drop.

Polling Method 2

Base Station is the Client, and Jetson/Raspi is the Server.

Client sends a request every 250ms to the Jetson/Raspi with the full rover control state.

Server (Jetson/Raspi) determines Fail State: If client misses poll timeout, fail condition.

Instant Control Method

Base Station is the client, and Jetson/Raspi is the server.

Server sends a request whenever controller input is changed, could either be the full state or just the thing that changed.

Fail State is allways Unsafe: No way to determine fail condition.

Command Method

Base Station is the Client, and Jetson/Raspi is the Server.

Server sends a request indicating not the control state, but an approximation of what that control state would cause during 250ms; a command. So, if the joystick is set to forwards, the command is "move forwards for 250ms at velocity 0.954". The server then translates that to holding the joystick at that velocity for 250ms before resetting it to zero.

Fail State is allways Safe: Commands are scoped to a time limit.

Getting the Realsense feed from the SBC to the Basestation

Naive Approach

Use USB-IP! It will map the SBC's usb port to the Basestation, allowing the Basestation to use the Realsense as if it's directly connected to it.

Step 1. On the SBC

Install usbip:

sudo apt install linux-tools-nvidia-tegra

List all available USB devices:

usbip list -l

Bind the Realsense:

usbip bind -b [Realsense Bus ID, should look something like #-#.#]

Step 2. On the basestation