Friendly Fire
University of Pennsylvania · ESE 3500 Embedded Systems · Spring 2026 final project
Devan Malik Marko Mijatovic Kim Huang Victor Wanjohi
A working IR laser-tag system: a handheld blaster, a chest-mount vest, and a BLE web dashboard that runs the match.
This repository is the class writeup and photo record for a four-person ESE 3500 team project. I keep it here as a portfolio copy of that work.
How it works
The blaster fires a 940 nm IR pulse on a valid trigger, with a 500 ms inter-shot cooldown, an ammo counter on an ST7735 LCD, piezo feedback, and shake-to-reload from an MPU6050 (I2C, ≥20 Hz, 2g for three samples). Firmware lives on an ATmega328PB.
The vest detects hits with a TSOP38238 receiver, drops remaining lives on three LEDs, and ships health / elimination state over UART to a Feather ESP BLE radio within 500 ms of a state change. A web dashboard can RESET both MCUs back to full health, full ammo, and ALIVE.
Both units run off 5 V USB power banks.
Project video
Photos
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Specifications
Software (SRS)
- SRS 01: Blaster firmware drives the IR LED for 0.5 s after a valid trigger so every shot produces a consistent, identifiable pulse.
- SRS 02: Minimum inter-shot interval of 500 ms (±50 ms). Extra trigger presses during cooldown are ignored.
- SRS 03: Ammo decrements on each valid shot; firing stops at zero. LCD ammo updates within 100 ms of the shot.
- SRS 04: Reload is shake-only, via the MPU6050. A valid shake restores ammo to maximum.
- SRS 05: Vest firmware sends health and elimination state to the BLE module over UART within 500 ms of a game-state change.
- SRS 06: A RESET command from the web app over BLE returns both MCUs to ready (full health, full ammo, ALIVE) within 1 s.
- SRS 07: MPU6050 sampled over I2C at ≥20 Hz. Shake-to-reload fires when acceleration exceeds 2g on any axis for at least three consecutive samples.
Hardware (HRS)
- HRS 01: NPN-driven 940 nm IR LED at ~50 mA, detected by a TSOP38238 at ≥3 m indoors.
- HRS 02: Vest IR receiver covers frontal hits.
- HRS 03: ST7735 LCD readable indoors, ≥5 fps for ammo / game state.
- HRS 04: Feather ESP radio for the web dashboard, stable indoors out to ~5 m.
- HRS 05: Piezo on the blaster ≥65 dB at 30 cm, with distinct fire / reload / empty tones.
- HRS 06: Each unit powered by a 5 V USB power bank (≥5000 mAh) for ≥60 minutes of play.
- HRS 07: ATmega328PB at 16 MHz, 5 V, 100 nF ceramic decoupling on VCC; subsystem current ≤500 mA in normal operation.
- HRS 08: Three vest LEDs for remaining lives, readable from ≥2 m indoors; one LED drops per valid hit.
Notes
The gameplay loop worked: IR hit detection, ammo / cooldown, shake-to-reload, and BLE status all came up as a single system. The hard parts were getting the IR LED consistent and then surviving the jump from a bench prototype into an enclosure — wiring and mechanical robustness bit us later than they should have. Earlier integration and a cleaner interconnect would be the first changes on a second pass.