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Wiring: RS-232 serial

Serial gear (projectors, older receivers, screen controllers) speaks RS-232, which is ±12 V — you must not wire it straight to an ESP32’s 3.3 V UART. Put a level shifter (a MAX3232 board) between them.

RS-232 serial wiring through a MAX3232 level shifter 3.3 V TTL UART RS-232 ±12 V your TX → device RX ESP32 dev board 3V3 TX RX GND 3232 MAX3232 level shifter T1IN R1OUT GND VCC T1OUT R1IN GND DB9 3 TXD 2 RXD 5 GND
The MAX3232 shifts the ESP32's 3.3 V UART to RS-232 ±12 V. The TTL side runs straight through; the RS-232 side crosses.
  • TX↔RX are crossed (your TX goes to the device’s RX). Many projectors also need a null-modem (crossover) cable — check the device’s manual; a straight cable that does nothing usually means TX/RX aren’t crossed.
  • Baud must match the device’s menu (Epson 9600, screens often 2400, BenQ configurable). Set it in the driver, not the firmware.

The proxy’s serial role is a dumb pipe (RS-232 over TCP) — all the protocol lives in the hub driver (Epson, BenQ, Screen, …), so one proxy serves whatever you point at it.