Using the esp32 as a bluetooth repeater.

[Baza1969]

Hi,
I'm very new to esp32 coding.
.. having Googled until I'm blue in the face - I can't find anything to help.
All Bluetooth tutorials I've found are about the esp32 receiving data only - or swapping text between serial monitor on Arduino IDE and a serial Bluetooth connect app on my phone. Most are BLE, where I need classic raw serial RFCOMM reads and writes.

I have a Bluetooth (classic) controlled guitar amplifier that is controlled by an app. the app sends audio for 'play-along' backing music plus instruction to the amp to change sound (eg from a rock guitar sound to an acoustic guitar - there are 4 sound presets) it's simple raw serial RFCOMM reads and writes over bluetooth.

What I'm trying to do is have an esp32 bridge between the app and the guitar amplifier using Bluetooth via mac addresses.
On this esp32 bridge device, I want to wire 4 footswitches to allow me to send the preset code and therefore change the amp sound via footswitch (allowing me to keep my hands free for playing - whilst allowing normal communication to continue between the tablet and the guitar amp)
So in a nutshell, allow the app to talk to the guitar amp as usual, but occasionally inject a preset command to change the guitar sound preset via the press of a footswitch.
Below are the data that need to be sent to select one of the 4 presets.

Preset1 = "01fe000053fe1a000000000000000000f00124000138000000f779"
Preset2 = "01fe000053fe1a000000000000000000f00123010138000001f779"
Preset3 = "01fe000053fe1a000000000000000000f00125020138000002f779"
Preset4 = "01fe000053fe1a000000000000000000f00120030138000003f779"

Based on this interesting work by sound shed..
https://github.com/soundshed/spork/blob ... n/spork.py

Could anyone suggest a way forwards? - I plan on using Arduino Ide - but I'm happy to use what ever suits.
many thanks for your time!