Robot Swarm using ESP-NOW Communication

Swarm robotics is usually taught as simulation — dozens of agents on a screen, no radios, no dropped packets, no dead batteries. The moment you put radios on real robots, the interesting problems appear: who hears whom, what happens when an acknowledgement never arrives, how formations survive a robot that stops responding. Wi-Fi and Bluetooth both drag in access points, pairing and latency that make multi-robot coordination painful. ESP-NOW, Espressif's connectionless peer-to-peer protocol, is the purpose-built answer: short packets, millisecond latency, no infrastructure. This project builds a real three-robot swarm on it — one controller, three ESP32 differential-drive robots, formation broadcasts with acknowledgements and retries, 10 Hz position telemetry, and ultrasonic collision override that works even if the radio link dies. The console makes the invisible visible: arena positions, packet log, delivery rate and round-trip latency. Formations are design targets measured on the buyer's own floor — range and loss depend on the room, antennas and interference, and the report says so.

1. Each robot ESP32 registers the controller's MAC address as an ESP-NOW peer at boot — no Wi-Fi association is ever needed.
2. The operator picks a formation on the console; the controller broadcasts a formation packet with each robot's target x/y slot (up to 250 bytes).
3. Robots acknowledge; the controller retries missing acks up to 3 times and the console logs the ack count per broadcast.
4. Followers run a proportional controller driving their differential-drive motors toward their assigned slots; the leader follows console joystick commands.
5. Every robot streams position, heading, battery and RSSI back at 10 Hz; the console renders the arena map and link statistics live.
6. Ultrasonic sensors run a local loop on each robot: an obstacle inside the stop distance halts the motors regardless of what the radio says.
7. The telemetry view aggregates delivery rate and round-trip latency; the report's test procedure has the buyer measure range, loss and latency in their own room.

Tech stack:

• 4x ESP32 DevKit (1 controller + 3 robots), Arduino-core firmware
• 3x differential-drive robot chassis kits (motors, wheels, caster)
• ESP-NOW peer-to-peer protocol (connectionless, 250-byte frames)
• Ultrasonic distance sensors (local collision override per robot)
• Proportional formation-follower controller firmware
• Li-ion battery packs with charging guidance
• Single-file HTML/CSS/JS command console (arena, telemetry, packet log)

• [ESP-NOW peer-to-peer link] Controller and robots communicate with connectionless ESP-NOW frames — no router, no pairing, no cloud; up to 250-byte packets with millisecond-scale latency.
• [Formation control] Broadcast line, triangle, cluster and scatter formations; each follower runs a proportional controller toward its assigned slot while the leader follows the console joystick.
• [Acknowledged broadcasts] Every formation packet expects per-robot acks; missing acks trigger up to 3 retries, and the console shows exactly who acknowledged and who didn't.
• [Live arena console] The command console renders robot positions and headings in real time from 10 Hz ESP-NOW telemetry, with per-robot battery bars and RSSI.
• [Packet + latency telemetry] Packet log, delivery-rate counter and a 60-second round-trip latency chart make the wireless link itself the observable under test — design target ≥ 95% delivery in lab range.
• [Ultrasonic collision override] Each robot's ultrasonic sensor halts it independently of the radio link — the safety layer that works even during a comms blackout.
• [Leader-follower roles] SWARM-01 leads (console-driven), SWARM-02/03 follow; roles are firmware constants, so the viva can discuss reassignment and failure handling.
• [Complete build docs] Chassis assembly guide, ESP-NOW peer-registration procedure (MAC pairing), tuning guide for the follower gains, and commented firmware.

• Complete firmware: controller (broadcast, ack/retry, joystick) + robot (peer link, follower control, telemetry, collision override)
• Chassis assembly and wiring guide for all three robots
• ESP-NOW peer-registration (MAC pairing) procedure
• Command console web app (swarm control + telemetry views)
• Follower-gain tuning guide
• Project report PDF (background, protocol design, control design, test procedure)
• PPT presentation for final review
• Viva Q&A preparation document (ESP-NOW vs Wi-Fi/BLE, formation control, proportional control, acks/retries, link budget)
• Setup guide (first power-up, peer registration, first formation)

• Delivery rate and latency are design targets measured on the buyer's own robots — walls, Wi-Fi interference and antenna orientation change them, and the report documents the measurement procedure rather than pre-claiming figures.
• Three robots is the tested configuration; larger swarms need broadcast scheduling work the report flags as future scope.
• Position tracking in the console comes from each robot's own odometry/telemetry, not an external motion-capture system — absolute arena accuracy is approximate.
• Ultrasonic sensors see flat obstacles well and soft/angled ones poorly; the collision override is a safety layer, not a mapping system.
• Battery life limits demo sessions; the report's power notes size expectations honestly.