STM32-Jetson Comms Implementation

Overview

Here we want to define what a communication system between the STM32 and Jetson need to exchange (refer to the Exchanged Data specifications from last year), when it will be communicated (event-driven vs. batch) and the overall data schema.

Requirements

Comm Subsystem Requirement	Competition Requirement	Priority
Send the lattitude and longtitude in decimal degrees to the flight controller after a successful QR scan as well a begin takeoff command	Task 2: Send coordinates after QR Scan	HIGH
At a specified rate, send the IMU and GPS data to the jetson	Task 2: Receive IMU data	HIGH
At a specified rate, send the current location of the detected target to the flight controller	Task 2: Track targets	LOW

Schema

Flight Controller → Jetson (FOJI)

// Format schema here as JSON
{
  gpsCoordinates: {
    lattitude: 8 byte double,
    longtitude: 8 byte double,
    altitude:  8 byte double
  },
  eulerAnglesOfPlane (Radians): {
    yaw: 4 byte float,
    pitch: 4 byte float,
    roll: 4 byte float
  }
}

Note that in this iteration, eulerAnglesOfCamera comes from the gimbal controller rather than the flight controller.

Jetson → Firmware Controller (FIJO)

{
  takeoffCommand: 4 byte boolean,
  qrScanFlag: 4 byte boolean,
  detectFlag: 4 byte boolean, 
  gpsCoordinates: {
    lattitude: 8 byte double,
    longtitude: 8 byte double
  }
}

Flags

These flags are booleans that are mutually excusive.

qrScanFlag: If true, then the gpsCoordinates are the coordinates that we got from the QR Scan.
detectFlag: If true, then the gpsCoordinates are the coordinates of the detected target. (used for hover mode)

Encoding

Encode the schema as a semicolon separated value with start and end bits.

FOJI

Start bit is a $ followed by FOJI

$FOJI;lattitude;longtitude;altitude;yaw;pitch;roll

Total Message Size: 47 bytes

FIJO

Start messages with a '$' sign followed by the string “FIJO”

$FIJO;takeoffCommand;qrScanFlag;detectFlag;lattitude;longitude

Total message size: 38 bytes