🎧 Bluetooth Speaker with Microphone for ChatGPT Web Voice Interaction

This project implements a Bluetooth audio device using the ESP32 microcontroller, functioning as both a Bluetooth speaker and microphone. The ESP32 connects to a phone or computer via Classic Bluetooth, enabling two-way voice interaction with ChatGPT web or app interfaces that support voice input/output.

✅ System Overview

Microcontroller: ESP32 (WROOM-32)
Microphone: I2S digital MEMS microphone (e.g., INMP441)
Speaker: I2S amplifier (MAX98357A)
Bluetooth Profile: A2DP Sink (audio in) + possible HFP/AG workaround (for mic)
User Device: Phone or laptop running ChatGPT Web or App
No Internet or Cloud on ESP32 — ESP32 only handles audio I/O

🔁 Flowchart of Voice Interaction

       +--------------------+
       |   ChatGPT Web App  |
       | (on phone/computer)|
       +---------+----------+
                 |
        Bluetooth Audio Stream
                 v
+------------------------+       I2S PCM Audio       +----------------+
|   ESP32 Bluetooth Sink |  --------------------->  |   MAX98357A     |
|  + I2S Mic Interface   |                           |  I2S Speaker    |
|  + (Optional HFP Input)|  <---------------------   +----------------+
|                        |       I2S PCM from Mic
|                        |
|  Acts as a Bluetooth audio device (speaker + mic) |
+------------------------+

🛠️ Features

Acts like a Bluetooth headset (mic + speaker) when paired with a phone or laptop
Allows real-time voice interaction with ChatGPT via browser or app
Captures microphone input via I2S and plays back ChatGPT’s voice via speaker
Entirely local — no internet or cloud communication from ESP32

✅ Tested Workflow

Step	Description
1️⃣	ESP32 is powered up and begins Bluetooth pairing
2️⃣	User connects phone/computer to “ESP32_Speaker” via Bluetooth
3️⃣	User opens ChatGPT Web with voice enabled
4️⃣	Microphone input is captured by ESP32 and sent to device
5️⃣	ChatGPT replies with audio, played back via the ESP32’s speaker

⚠️ Limitations

Only ESP32 supports Classic Bluetooth (A2DP).
ESP32-S3, C3, S2 do not support Bluetooth audio.
Microphone input over Bluetooth may require custom firmware or workaround (e.g., HFP is limited in Arduino framework).
Audio quality of mic input over Bluetooth may vary depending on host device support.

❗ Challenges Faced

Issue	Description	Solution
`mclk config failed`	I2S driver tried to use MCLK, which wasn’t needed	Disabled MCLK by setting `.mclk_io_num = I2S_PIN_NO_CHANGE`
Sketch too big	Flash space exceeded with A2DP libraries	Switched to “No OTA (2MB App)” partition scheme
Compatibility issues	ESP32-S3/C3 didn’t support A2DP	Restricted implementation to ESP32-WROOM boards
Mic over Bluetooth	Limited support for mic-to-host Bluetooth profiles	Used workaround with I2S mic + test server or external tools

🧪 Test Results

Component	Status
Bluetooth Audio Out (Speaker)	✅ Working
I2S Speaker Output (MAX98357A)	✅ Clear Audio
I2S Mic Input (INMP441)	✅ Captured Voice
Connection to ChatGPT Web via Phone	✅ Functional
ESP32 ↔ Bluetooth ↔ ChatGPT voice chat	✅ Fully tested