Two STM32-based drones on a shared CAN bus. Drone A leads. Drone B follows in formation. Real-time position sharing, priority-based messaging, automatic fault detection.

drone-can-network/
├── Common/
│   ├── Inc/
│   │   ├── can_messages.h     # All CAN message IDs and payload structs
│   │   └── can_driver.h       # Driver API — init, send, callbacks
│   └── Src/
│       └── can_driver.c       # Full driver implementation
├── Drone_A/
│   ├── drone_a_main.h
│   └── drone_a_main.c         # Lead drone — broadcasts position, monitors B
├── Drone_B/
│   ├── drone_b_main.h
│   └── drone_b_main.c         # Follower drone — formation control from A's pos
└── docs/
    └── message_table.md       # CAN ID reference

Lower ID = higher priority. CAN arbitration ensures emergency frames always win without collision or data loss.

STM32 (Drone A)                     STM32 (Drone B)
   CAN1_TX ──► TJA1050 ──┐   ┌── TJA1050 ◄── CAN1_TX
   CAN1_RX ◄── TJA1050 ──┤   ├── TJA1050 ──► CAN1_RX
                          │   │
                    ┌─────┴───┴─────┐
             [120Ω] │  CAN-H CAN-L  │ [120Ω]
                    └───────────────┘
                      twisted pair

Required components per drone:

• STM32F4 (or F1/F3 — any with CAN peripheral)
• TJA1050 or MCP2551 CAN transceiver
• 120Ω termination resistor at each end of the bus
• Twisted pair wire (any length up to ~40m at 500Kbps)

Step 1 — copy Common/ into your STM32CubeIDE project

Step 2 — initialise CAN in CubeMX

• Mode: Normal
• Baud: 500 Kbps (Prescaler=6, BS1=11, BS2=4 at 84MHz APB1)
• Enable CAN global interrupt

Step 3 — call init and process

For Drone A:

// in main.c
#include "drone_a_main.h"

int main(void) {
    HAL_Init();
    SystemClock_Config();
    MX_CAN1_Init();

    DroneA_Init();

    while (1) {
        DroneA_Process();
        HAL_Delay(10);  // or remove if using RTOS
    }
}

For Drone B — same pattern but call DroneB_Init() and DroneB_Process().

Step 4 — fill in sensor stubs

Look for /* TODO: */ comments in drone_a_main.c and drone_b_main.c. Replace the stub functions with your actual GPS, IMU, and ADC reads.

Drone B holds a fixed offset from Drone A using a simple P-controller. Default: 2m east, same altitude.

Change offset in drone_b_main.c:

#define FORMATION_OFFSET_X_CM    200   // 2m east
#define FORMATION_OFFSET_Y_CM      0
#define FORMATION_OFFSET_Z_CM      0

Tune the proportional gain:

const int16_t Kp = 3;   // cm/s per cm of position error

For real flight: replace the P-controller with a full PID loop and feed the output into your flight controller's velocity setpoint input.

• CAN FD — increase DLC to 64 bytes if you need larger payloads (sensor fusion data, config frames)
• More drones — add DRONE_C_NODE_ID = 0x03 in can_messages.h, copy Drone B, change formation offset
• GCS link — connect a USB-CAN adapter (e.g. PEAK PCAN) to the bus, use python-can to read/send from PC
• Logging — send raw CAN frames to SD card using the heartbeat seq number as a timestamp reference

• STM32F411 Nucleo (500 Kbps, TJA1050 transceiver)
• STM32F103 Blue Pill (same config)

Hardware not available? Test with two STM32 dev boards connected by 3 wires (CAN-H, CAN-L, GND) with a 120Ω resistor across H and L at each end.

Author: Arya · CIT Chennai
Target: STM32 HAL · CAN 2.0A (11-bit ID) · ISO 11898