Hardware & Wiring

Kegboard v4 targets generic ESP32 devkits. There is no custom PCB (yet); the legacy kegboard-mini/mega/coaster boards ran the AVR firmware and live on the arduino branch.

Supported boards

Board package

Chip

Notes

boards/esp32-s3-devkitc-1.yaml

ESP32-S3

Reference target. Native USB (no adapter to flash), ample GPIO, PSRAM headroom.

boards/esp32-devkit.yaml

ESP32 (WROOM-32)

What most people already have in a drawer.

boards/esp32-c6-devkitc-1.yaml

ESP32-C6

Forward-looking: WiFi 6, Thread/Zigbee radios.

Other ESPHome-supported ESP32 variants work; write your own board package with the same substitution names.

Pin maps

Defined as substitutions in each board package; override them in your config to relocate a peripheral.

Substitution

S3

Classic

C6

Used by

meter0_pin–meter3_pin

4–7

4, 5, 13, 14

4–7

Flow meters

onewire_pin

15

16

10

Thermo 1-Wire bus

relay0_pin, relay1_pin

16, 17

17, 18

11, 18

Relays

buzzer_pin

18

19

19

Piezo buzzer

led0_pin, led1_pin

8, 9

21, 22

20, 21

Flow LEDs

rfid_rx_pin

44

23

22

RFID reader UART

onewire_auth_pin

21

25

23

iButton 1-Wire bus

The maps avoid each chip’s landmines: strapping pins, flash/PSRAM pins, native-USB pins, and (on the classic ESP32) GPIO 34–39, which are input-only with no internal pull-ups and so cannot bias an open-collector meter.

Flow meters

Kegboard supports open-collector meters — typically hall-effect sensors that pulse once per fixed volume as liquid passes. Meter inputs use the internal pull-up and count falling edges; wire the meter’s output straight to the pin, its ground to ground.

ESP32 GPIOs are not 5 V tolerant. Open-collector meters are safe on a 3.3 V pull-up even when powered from 5 V, because they only ever pull the line to ground. Meters with a push-pull 5 V output will damage the ESP32 and need a level shifter or divider. Check your meter before wiring it.

The default calibration (ml_per_tick: 0.185, ~5.4 ticks/mL) matches the SwissFlow SF800 and its clones. Other meters work; set ml_per_tick accordingly (a Vision 2000 is ~2200 ticks/L → 0.4545).

Temperature sensors

DS18B20/DS18S20 sensors on the onewire_pin bus, via ESPHome’s one_wire and dallas_temp. Any number of sensors on one bus; each needs the usual 4.7 kΩ pull-up to 3.3 V (many breakout probes include it).

Authentication readers

  • 125 kHz RFID: RDM6300-class readers (the ID-12 lineage) on rfid_rx_pin via UART at 9600 baud, using ESPHome’s rdm6300. TX-only — nothing is wired back to the reader.

  • iButton: a second 1-Wire bus on onewire_auth_pin, read by kegboard_onewire. Kept separate from the thermo bus so a wet hand stays away from the keg sensors.

  • Anything else: any ESPHome reader (wiegand, pn532, rc522, …) can feed kegboard_auth — see extending.

Relays and valves

packages/relays.yaml defines two GPIO relay outputs, each with a watchdog that switches it off relay_watchdog_timeout (default 10 s) after it turns on — see the package’s notes before putting a grant-driven valve on one. Use a relay module rated for logic-level (3.3 V) input, or a transistor driver. What’s downstream is usually a solenoid valve; give it its own supply and a flyback diode if the module lacks one.

Buzzer and LEDs

A passive piezo on buzzer_pin plays the legacy Kegboard melodies (packages/buzzer.yaml); an active buzzer generates its own tone and will ignore them. Flow LEDs are ordinary GPIO LEDs with resistors, wired per the pin map and driven from on_pour_start/on_pour_end automations.