FED4 (Feeding Experimentation Device) is an open-source Arduino library for mouse operant training on board v1.7. Hardware details and chipsets: CHIPSETS.md.

Hardware features (v1.7)

• MCU — ESP32-S3
• Feeding — stepper pellet dispenser with photogate well sensing and jam-clear paths
• Nose pokes — three ESP32-S3 capacitive touch pads (left / center / right) with light-sleep wake
• Photogates — four IR gates (left / center / right poke lanes + pellet / drop path)
• Display — Kyocera TN0216 320×176 MIP reflective mono panel (SPI + VCOM)
• Storage — microSD (SPI) for session CSV logging
• Clock — DS3231 RTC
• Environment — BME680 (temp / humidity / pressure / gas), VEML7700 ambient light
• Battery — LiPo monitoring via MAX17048 fuel gauge
• Motion / proximity — PIR (EKMB1107112); VL53L1X time-of-flight; LIS3DH accelerometer on board
• User I/O — three front buttons; MCP23017 GPIO expander (rails, haptics, solenoids, display control)
• Feedback — WS2812 front RGB strip, red status LED, haptic motor, MAX98357A I2S speaker amp
• Expansion — TRRS / GPIO header (audio or digital); dual solenoid drivers; user expander pins; optional servo/INT
• Power — switched peripheral rails (PSV2 / PSV3 via TPS22917) for sleep current control
• Optional wireless — Hublink BLE sync

Library sketches stay small via an event-driven idle path: waitUntil() → act → update().

In-lab test firmware flashes (version on the display, CSV LibraryVer) are tracked in docs/firmware/.

Examples

Sketch	Role
BasicFED4	Left poke → feed (starter program)
FreeFeeding	Replace pellet when taken
2_UnitTests/	Hardware bring-up / domain checks

More programs will return under examples/1_Programs/ as domains are verified. Deeper API notes live in docs/wiki/ and the GitHub Wiki.

In Development

Open work tracked in detail in examples/2_UnitTests/SRC_AUDIT.md:

• Rebuild menu + silence UX for v1.7 display
• Retest / clean button holds (silence, menu, Mario / jingles)
• Port remaining behavioral programs from archive → 1_Programs
• PIR / motion idle path (deferred to v1.8 counter IC)
• Revisit ActivityMonitor when that sketch is unarchived
• Sense / camera — TRRS TRIG + UART path in examples/3_Submodules/ (FED4::senseSyncTime / senseTrigPulse). Validate chamber lighting + fixed AE under strip white.
• Characterize touch / SD card write duration to determine max touch rate