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Wiring: other scenarios

Beyond IR and serial, a proxy can switch pins and act as a Bluetooth remote.

Projector screen / lift (gpio.out or serial)

Section titled “Projector screen / lift (gpio.out or serial)”

Motorised screens are either dry-contact (up/down/stop relays) or RS-232.

  • Dry contact: drive a small relay board from gpio.out pins; wire the relay contacts to the screen’s trigger terminals.
  • RS-232: wire as in serial and use the Screen driver.

For the dry-contact case, a gpio.out pin drives a relay module (its own transistor and flyback diode keep the coil off the ESP32), and the relay’s isolated COM/NO contacts close the screen controller’s trigger terminals.

A GPIO driving a relay module for a dry-contact screen trigger GPIO switches the coil ESP32 dev board 3V3 TX RX GND RLY Relay module IN VCC GND COM NO dry contact Screen trigger
A relay board isolates the screen's trigger terminals from the ESP32 — the contacts just close, so it suits any dry-contact input.

12 V trigger in/out (gpio)

Section titled “12 V trigger in/out (gpio)”
  • Out: a GPIO through a transistor/relay can pulse a 12 V trigger to power an amp on with an activity.
  • In: an opto-isolator from a 12 V trigger into a GPIO lets reMaestro react to another device turning on.

An opto-isolator is the safe way to read a trigger: the 12 V side lights an LED inside the package, a phototransistor on the other side sees it, and there is no electrical path between them — so nothing can put 12 V onto a 3.3 V pin.

A 12 V trigger read by a GPIO through an opto-isolator 1 kΩ 12 V in reads as a GPIO input Amplifier 12 V trigger out PC817 opto-isolator no electrical path A K C E ESP32 dev board 3V3 TX RX GND
The opto-isolator is the point: a 12 V trigger can tell the ESP32 an amplifier came on without any path that could put 12 V on a 3.3 V pin.

Bluetooth HID (bt.hid)

Section titled “Bluetooth HID (bt.hid)”

The ESP32 can pair to a TV/streamer as a Bluetooth remote and relay navigation with no IR and no vendor API — driven by the HID proxy driver. No extra wiring; just power the ESP32 near the device and pair.

An ESP32 acting as a Bluetooth HID remote to a streamer Bluetooth HID — no cable ESP32 dev board 3V3 TX RX GND Apple TV paired as a remote
Nothing to wire but power: the proxy pairs as a Bluetooth remote and sends the same button presses a handset would.

Bluetooth remote in (bt.host)

Section titled “Bluetooth remote in (bt.host)”

The same radio works the other way. In bt.host the board pairs to a Bluetooth remote and relays what it heard; the hub decides what it meant, so the remote drives activities from a room the hub itself can’t hear. Like bt.hid it needs no pins — power the ESP32 within range of the remote and pair.