Hi,
it is totaly easy and you have luck that I’m just sitting in front of boring work and need some deflection.
You need an ESP8266 board: Wemos D1 mini (2,5€ , Node MCU or any other board with USB/TTL converter and 5V to 3.4V regulator will do. Or a ESP01 module if you prefer the hard way and save a few bucks 
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Than you need a RS232 to TTL converter board with a MAX3232 (certainly others will do the job too) and 4 female to female jumper wires (in some modules included). You can get this for 1€. Connect GND and 3.3V. Connect D7 (GPIO15) to TX and D8 (GPIO13) to RX.I Removed the screws and metal shield to plug it into my projector directly.
Finally a minimum 500mA USB plugpack. I used an old charger with 500mA. The ESP is well known for his power spikes during transmission and most boards do not have a sufficient capacitor to compensate this.
I used the ESP-Link firmware follow the instructions to flash and first connection. There are other Firmware available like ESPeasy.
I played around with different pin settings … this worked for me:
I picked the ESP-Link firmware because it gives you a “man in the middle” debug function using the build in console feature. My Bridge is running for more than one year 24/7 without any problems.
In the future I will try to use use the HTTP Binding and program the features I need because the dedicated binding crashes after a few weeks and I have to restart openHAB to get it up and running.
Would be nice to see your result.
Christian